Physical Principles of Respiratory Care. Egan Chapter 6. Physical Principles of Respiratory Care. States of Matter Change of State Gas Behavior Under Changing Conditions Fluid Dynamics. II. Change of State. Liquid-Solid Phase Changes Melting Freezing Properties of Liquids - PowerPoint PPT Presentation
TRANSCRIPT
Physical Principles of Respiratory Care
Egan Chapter 6
Physical Principles of Respiratory Care
I States of MatterII Change of StateIII Gas Behavior Under Changing
ConditionsIV Fluid Dynamics
II Change of StateA Liquid-Solid Phase
Changes1 Melting2 Freezing
B Properties of Liquids1 Pressure in Liquids2 Buoyancy
(Archimedesrsquo Principle)3 Viscosity4 Cohesion and Adhesion5 Surface Tension6 Capillary Action
C Liquid-Vapor Phase Changes
1 Boiling2 Evaporation Vapor
Pressure and Humidity
D Properties of Gases1 Kinetic Activity of Gases2 Molar Volume and Gas
Density3 Gaseous Diffusion4 Gas Pressure5 Partial Pressure (Daltonrsquos
Law)6 Solubility of Gases in
Liquids (Henryrsquos Law)
II Change of StateA Liquid-Solid Phase Changes
1 Melting2 Freezing
httpwwwyoutubecomwatchv=j2KZmRIKea8Start at 315
5
A Liquid-Solid Phase Changes
1 Melting
When a solid is heated what happens to its kinetic energy
What happens to its intermolecular forces
6
A Liquid-Solid Phase Changes2 Freezing
When a liquid is cooled what happens to its kinetic energy
What happens to its intermolecular forces
A Liquid-Solid Phase Changes
Intermolecular forces
8
A Liquid-Solid Phase Changes Melting and Boiling
Melting PointThe temperature at which a solid
converts to a liquid Boiling Point
The temperature at which a liquid converts to the gaseous state
Substance Melting Point Boiling Point
WaterOxygen
0degC-219degC
100degC-183degC
9
A Liquid-Solid Phase Changes Melting and Boiling
Latent HeatThe amount of heat needed for a
substance to change its state of matter Latent heat of fusion
The amount of heat needed to change a solid to a liquid
Latent heat of vaporizationThe amount of heat needed to change a
liquid to a gas
10
A Liquid-Solid Phase Changes
Ice
Water
SteamLatent heat of vaporization
Latent heat of fusion
II Change of StateB Properties of Liquids
1 Pressure in Liquids2 Buoyancy (Archimedesrsquo Principle)3 Viscosity4 Cohesion and Adhesion5 Surface Tension6 Capillary Action
B Properties of Liquids Liquid Oxygen http
wwwyoutubecomwatchv=ndtmfDoI8PM
13
B Properties of Liquids Liquid molecules also possess attractive
forces but these forces are much weaker in
liquids than in solids
Liquid molecules have greater freedom of movement and possess more KE than solids This is why liquids take the shape of their
container And are capable of flow
Liquids cannot be easily compressed
14
B Properties of Liquids
1 Pressure in Liquids Is the same at any specific depth
regardless of the containerrsquos shape Is exerted equally in all directions
15
B Properties of Liquids
1 Pressure in Liquids Pascalrsquos Principle A confined liquid
transmits pressure equally in all directions
16
B Properties of Liquids
1 Pressure in Liquids Pascalrsquos Principle Downward
17
B Properties of Liquids
1 Pressure in Liquids Liquids are capable of flow Pascalrsquos Principle Sideways
18
B Properties of Liquids
1 Pressure in Liquids Pascalrsquos Principle Upward
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
B Properties of Liquids6 Capillary Action A phenomenon in which a liquid in a small
tube moves upward against gravity
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
B Properties of Liquids6 Capillary Action
httpwwwyoutubecomwatchv=mdkeZbm0cCI
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
B Properties of Liquids6 Capillary Action Clinical Examples
Capillary blood stick
httpwwwyoutubecomwatchv=q5J1cCyrASs
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
B Properties of Liquids6 Capillary Action Clinical Examples
Absorbent wick humidifiers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Liquid-Vapor Phase Changes1 Boiling2 Evaporation Vapor Pressure and Humidity
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Liquid-Vapor Phase Changes
49
Liquid to vapor phase changes (vaporization) 2 types of vaporization
Boiling heating liquid to temperature at which its vapor pressure exceeds atmospheric pressure Boiling point of most liquefied gases is very low
Liquid oxygen boils at -183degC Evaporationwhen liquid changes into gas at temperature below
its boiling point Evaporation requires heat The heat energy required for
evaporation comes from the air next to the water surface As the surrounding air loses heat energy it cools This is the principle of evaporative cooling which was previously described
Water enters atmosphere via evaporation when at temperature lower than its boiling point (water vapor)
Molecular water exerts pressure called water vapor pressure Temperature influences evaporation most The warmer the air the more vapor it can hold
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
50
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Evaporation the change in
state of substance from a liquid to a gaseous state below its boiling point
Molecular water exerts a pressure called the water vapor pressure
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
51
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity
State of equilibrium for every molecule escaping into the air another returns to the water reservoir
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
52
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature The warmer the air the more water vapor it
can hold The capacity of air to hold water vapor
increases with temperature Thus the warmer the air contacting a water
surface the faster the rate of evaporation
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
53
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and Humidity
Influence of Temperature If water is heated its
kinetic energy is thus increased and thus more molecules are helped to escape from its surface
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
54
C Liquid-Vapor Phase Changes2 Evaporation Vapor Pressure and HumidityInfluence of Temperature
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
55
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Clinical Application
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
56
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and HumidityInfluence of PressureHigh atmospheric pressures impede vaporizationLow atmospheric pressures increase vaporization
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
57
C Liquid-Vapor Phase Changes
2 Evaporation Vapor Pressure and Humidity Influence of surface area The greater the available surface area of the
gas in contact with air the greater the rate of liquid evaporation
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
58
C Liquid Vapor Phase Chapges
2 Evaporation Water Vapor Pressure and Humdidty Humidity water in molecular vapor form Water vapor pressure the kinetic activity of
water molecules in air For the actual amount or weight of water
vapor in a gas to be found the water vapor content (absolute humidity) must be measured
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Liquid-Vapor Phase Changes
59
2 Evaporation Water Vapor Pressure and Humidity Absolute Humidity
aka water vapor content Actual amount (or weight) of water vapor
in gas Measured in mgL Varies w temperature amp pressure Air that is fully saturated w water vapor
has absolute humidity of 438 mgL at 37degC 760 mm Hg amp water vapor pressure of 47 mm Hg
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Relative humidity (RH)
When gas is not fully saturated Water vapor content can be expressed in
relative terms Ratio of its actual water vapor content to
its saturated capacity at given temperature
RH = Content (Absolute Humidity) x 100Saturated Capacity
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
62
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example At a temperature of 22degC air has
the capacity to hold 194 mgL of water vapor (this information comes from the table in Egan) If the absolute humidity in the air is 74 mgL what is the relative humidity
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
63
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Temperature = 22degC Capacity = 194 mgL of water vapor Water vapor content (AH) = 74 mgL RH = water vapor content x 100
capacity
httpwwwyoutubecomwatchv=CL5cgXwKUXc
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
64
C Liquid-Vapor Phase Changes
2 Evaporation Water Vapor Pressure and HumidityPercent Body Humidity The ratio of the actual water vapor content of
the gas to the water vapor capacity in a saturated gas at body temperature (37degC)
BH = water vapor content x 100 capacity at 37deg C
Capacity at 37degC is always 438 mgL
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
65
Clinical ApplicationAerosol Therapy2 Evaporation Water Vapor Pressure and Humidity Clinical Aplication
Aerosol Therapy
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
66
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example The American National Standards
Institute has set a water vapor content level of 30 mgL as the minimum absolute humidity required for patients whose upper airways have been bypassed This equals what body humidity
Water vapor content = 30 mgL BH = water vapor content x 100
capacity at 37deg C
67
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Humidity Deficit
The difference in water vapor content between inspired air and the saturated gas conditions present in the lungs
The amount of water vapor your body must add to the inspired gas to achieve saturation at body temperature
HD=438 mgLndashwater vapor content
68
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Example Using the previous example where water
vapor content = 30 mgL What is the humidity deficit HD=438 mgLndashwater vapor content
69
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Condensation The change of state from gas to
liquid Dew Point The temperature at which
condensation begins
70
C Liquid-Vapor Phase Changes2 Evaporation Water Vapor Pressure and Humidity Clinical Application
II Change of StateD Properties of Gases
1 Kinetic Activity of Gases2 Molar Volume and Gas Density
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Partial Pressure (Daltonrsquos Law)6 Solubility of Gases in Liquids (Henryrsquos Law)
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
72
C Properties of Gases Gases do not maintain their shape
and volume they expand to fill the available space
Gases are easily compressed and expanded
Gases are capable of flow (like liquids)
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Properties of Gases
1 Kinetic Activity of Gases Molecular attractive forces are extremely
weak in gases therefore gasses possess the greatest amount of KE their PE is minimal
Gas molecules travel at high speeds in random fashion with frequent collisions
The velocity of gas molecules is directly proportional to its temperature
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Properties of Gases
2 Molar Volume and Gas Density Molar Volume
1 gram molecular weight (gmw) or mole of any substance at a temperature of 0deg C (273 K) and a pressure of 1 atm occupies 224 L (molar volume) contains 6023 x 1023 (Avogadrorsquos
number) molecules
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Properties of Gases2 Molar Volume and Gas Density Molar Volume
Equal volumes of all gases under the same conditions must contain the same number of molecules
Molar volume = 224L
1 moleof Helium
1 moleof Oxygen
has the same number of molecules
ashellip
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
C Properties of Gases
2 Molar Volume and Gas Density Gas Density
Density the ratio of a substancersquos mass to its
volumemass per unit volume
Density = gmw 224 L
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Gas Densitybull A dense substance has heavy
particles packed closely together (Uranium is a good example of a dense substance)
bull Conversely a low density substance has a low concentration of light weight particles per unit volume (Hydrogen gas)
bull The density of any gas at STPD can be computed easily by dividing its molecular weight by the universal molar volume of 224 L
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
78
GMW O2 = N2 = He = CO2 =
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Density of Gases GRAM MOLECULAR WEIGHTS( GMW) The molecular weight of a
substance in grams To find the GMW of a medical gas we must know the atomic weights of several common chemical elements
Substance Symbol Atomic Weight
A) Hydrogen H 1B) Helium He 4C) Carbon C 12D) Nitrogen N 14E) Oxygen O 16F) Room Air 288
NOTE Nitrogen and Oxygen are found in the atmosphere in gaseous form as diatomic elements So oxygen gas will have an atomic weight of 16 X 2 or 32 and nitrogen gas will have an atomic weight of 14 X 2 or 28
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
80
Gas Density Example 1 What is the density of oxygen at STP Density = gmw
224 L
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Density of O2 O2 = 32 grams
O = 8x2= 16 O2 = 16 x 2 = 32
32224 = 142
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
82
Gas Density Example 2 What is the density of air Density = gmw
224 L
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Density of AirN= 14 x 2 = 28 O= 16 x 2 = 32
28 x 79 = 221216 x 21= 6722212 + 672 = 2884 224 = 128
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Density of Gases Gases are influenced by changes in temperature and
pressure Calculates under STP conditions Calculated by dividing volume occupied by 1 mole of
gas at STP that is 224 liters into the gram of molecular weight of that gas
Density = gram molecular weight 224 liters Example Density of O2 = Weight of O2 32g 224 liters =
143gL Gases such as Helium have far less density Oxygen has higher density than air and tends to
accumulate at the lowest point (Ex oxygen enclosure)
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
5 Daltonrsquos Law of Partial Pressures Daltonrsquos Law
the sum of the partial pressures of a gas mixture equals the total pressure
Partial pressure the pressure exerted by a single gas
in a mixture
119
Daltonrsquos Law of Partial Pressures
The partial pressure of any gas within a gas mixture is proportional to its percentage in the mixture
PB = PN2 + PO2 + PH2O + PAr + PCO2 + Pgases
120
Daltonrsquos Law of Partial Pressures
Air asymp 21 O2 and 79 N2
Fractional concentration of O2 = 021 Fractional concentration of N2 = 079 partial pressure = fractional concentration x
total pressure
PO2 =
PN2 =
121
Daltonrsquos Law of Partial Pressures What happens to PB PO2 and FiO2 as
altitude changes Why do mountain climbers use extra
oxygen at high altitudes
122
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed on Airplanes
123
Daltonrsquos Law of Partial Pressures
Hyperbaric Chambers
Physical Principles of Respiratory Care
Physical Principles of Respiratory Care
II Change of State
II Change of State (2)
A Liquid-Solid Phase Changes
A Liquid-Solid Phase Changes (2)
A Liquid-Solid Phase Changes (3)
A Liquid-Solid Phase Changes (4)
A Liquid-Solid Phase Changes (5)
A Liquid-Solid Phase Changes (6)
II Change of State (3)
B Properties of Liquids
B Properties of Liquids (2)
B Properties of Liquids (3)
B Properties of Liquids (4)
B Properties of Liquids (5)
B Properties of Liquids (6)
B Properties of Liquids (7)
B Properties of Liquids (8)
B Properties of Liquids (9)
B Pressure in Liquids
B Pressure in Liquids (2)
B Pressure in Liquids (3)
B Properties of Liquids (10)
B Properties of Liquids (11)
B Properties of Liquids (12)
Cohesion and Adhesion
Cohesion and Adhesion (2)
B Properties of Liquids (13)
B Properties of Liquids (14)
B Properties of Liquids (15)
B Properties of Liquids (16)
B Properties of Liquids (17)
B Properties of Liquids (18)
B Properties of Liquids (19)
B Properties of Liquids (20)
Surface Tension
B Properties of Liquids (21)
B Properties of Liquids (22)
B Properties of Liquids (23)
B Properties of Liquids (24)
B Properties of Liquids (25)
B Properties of Liquids (26)
B Properties of Liquids (27)
B Properties of Liquids (28)
B Properties of Liquids (29)
B Properties of Liquids (30)
C Liquid-Vapor Phase Changes
C Liquid-Vapor Phase Changes (2)
C Liquid-Vapor Phase Changes (3)
C Liquid-Vapor Phase Changes (4)
C Liquid-Vapor Phase Changes (5)
C Liquid-Vapor Phase Changes (6)
C Liquid-Vapor Phase Changes (7)
C Liquid-Vapor Phase Changes (8)
C Liquid-Vapor Phase Changes (9)
C Liquid-Vapor Phase Changes (10)
C Liquid Vapor Phase Chapges
C Liquid-Vapor Phase Changes (11)
Egan Table 6-3 page 112
C Liquid-Vapor Phase Changes (12)
C Liquid-Vapor Phase Changes (13)
C Liquid-Vapor Phase Changes (14)
C Liquid-Vapor Phase Changes (15)
Clinical Application Aerosol Therapy
C Liquid-Vapor Phase Changes (16)
C Liquid-Vapor Phase Changes (17)
C Liquid-Vapor Phase Changes (18)
C Liquid-Vapor Phase Changes (19)
C Liquid-Vapor Phase Changes (20)
II Change of State (4)
C Properties of Gases
C Properties of Gases (2)
C Properties of Gases (3)
C Properties of Gases (4)
C Properties of Gases (5)
Gas Density
Slide 78
Density of Gases
Gas Density Example 1
Density of O2
Gas Density Example 2
Density of Air
Density of Gases (2)
Density of Room Air
Practice
CO2
N2
He
80 He and 20 O2
C Properties of Gases (6)
C Properties of Gases (7)
Practice (2)
C Properties of Gases (8)
C Properties of Gases (9)
C Properties of Gases (10)
C Properties of Gases (11)
C Properties of Gases (12)
Diffusion CO2 vs O2
Gas Diffusion
Fickrsquos Law of Diffusion
Fickrsquos Law Diffusion is Directly Proportional to Surface Area
Fickrsquos Law Diffusion is Directly Proportional to Surface Area (2)
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat
Fickrsquos Law Diffusion is Directly Proportional to the Concentrat (2)
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn
Fickrsquos Law Diffusion is Inversely Proportional to Tissue Thickn (2)
Fickrsquos Law of Diffusion (2)
Fickrsquos Law
C Properties of Gases (13)
C Properties of Gases (14)
Atmospheric Pressure
Atmospheric Pressure at Sea Level
Clinical Pressure Measurements
Aneroid Barometer
Mechanical Manometer
Strain-gauge Pressure Transducer
C Properties of Gases (15)
Daltonrsquos Law of Partial Pressures
Daltonrsquos Law of Partial Pressures (2)
Slide 121
Daltonrsquos Law of Partial Pressures Why are oxygen masks Needed
Daltonrsquos Law of Partial Pressures Hyperbaric Chambers
Density of Room Air GMW OF ROOM AIR Room air is not a pure substance it is a mixture of gases
It contains about 79 nitrogen (N2) and 21 oxygen (O2) and small amounts of other gases We can determine the relative GMW for room air by multiplying the fractional concentration of each gas by its molecular weight and adding the results The GMW of room air can also be used to find the specific gravity of other medical gases because air is the usual standard for specific gravity of gases
Nitrogen Oxygen GMW air = (79 x 28) + (21 x 32) = ( 221 ) + ( 67 ) GMW air = 288 NOTE The above method can also be used to find the relative GMW of any
mixture of gases ie 60 He and 40 O2 or 95 O2 and 5 CO2
86
Practice Calculate the density of the following
gases 1 CO22 N23 He4 80 He and 20 O25 70 He and 30 O2
CO2 C= 12 O2 = 32
12 + 32 = 44 224 = 196
N2 N= 14 N2 = 14 x2 = 28
28 224 = 125
He He = 4 224 = 018
80 He and 20 O2 He = 80 x 4 = 32 O2 = 20 x 32= 64
32 + 64 = 96 224
043
91
C Properties of Gases
2 Molar Volume and Gas Density Density
Clinical Example HeliumOxygen Flow Rate Conversion
An oxygen flow meter is being used to administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18= 8 Lmin x 18= 144 Lmin
FYI the conversion factor for 7030 Heliox = 16
92
C Properties of Gases
2 Molar Volume and Gas Density An oxygen flow meter is being used to
administer 8 Lmin of an 80He20O2 gas mixture What is the actual flow rate of this gas mixture
Actual flow rate of 80he20O2= Flow rate x 18
FYI the conversion factor for 7030 Heliox = 16
93
Practice1 An oxygen flow meter is being used to
administer 10 Lmin of an 70He30O2 gas mixture What is the actual flow rate of this gas mixture
2 A therapist wants to deliver 15 Lmin of an 80He20O2 gas mixture What liter flow should the therapist set on the flowmeter
C Properties of Gases3 Gaseous Diffusion The movement of gas molecules from an
area of high concentration to an area of low concentration
httpwwwyoutubecomwatchv=_oLPBnhOCjM
95
C Properties of Gases
3 Gaseous Diffusion Grahamrsquos Law
The rate of diffusion of a gas is inversely proportional to the square root of its density
Lighter gases diffuse rapidly Heavy gases diffuse more slowly
96
C Properties of Gases3 Gaseous Diffusion Practical Application What is the GMW of O2
What is the GMW of CO2
According to Grahamrsquos Law which gas should diffuse faster
C Properties of Gases
6 Solubility of Gases in Liquids Henryrsquos Law The amount of gas that
dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas and its solubility coefficient
Solubility coefficient the volume of a gas that will dissolve in 1 mL of a given liquid at standard pressure and specified temperature
98
C Properties of Gases6 Solubility of Gases in Liquids Practical Example
0023 mL of O2 can dissolve in 1 mL of blood at 37degC
0510 mL of CO2 can dissolve in 1 mL of blood at 37degC
According to Henryrsquos Law which gas should dissolve faster
99
Diffusion CO2 vs O2 In the end CO2 diffuses about 19 x faster
than O2 because of its much greater solubility in blood
Gas Diffusion Fickrsquos law
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
What is the surface area of the alveoli
>
Fickrsquos LawDiffusion is Directly Proportional to Surface Area
A decreased alveolar surface area Alveolar collapse Fluid in the alveoli
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Fickrsquos LawDiffusion is Directly Proportional to the Concentration Gradient
Decreased alveolar oxygen pressure (PAO2) High altitudes Alveolar hypoventilation
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
Fickrsquos LawDiffusion is Inversely Proportional to Tissue Thickness
An increased alveolar tissue thickness Alveolar fibrosis Pulmonary edema
Decreases the diffusion of oxygen into the pulmonary capillary blood
Fickrsquos Law of Diffusion The rate of diffusion across a sheet of
tissue (the alveolar-capillary membrane) is Directly proportional to the
Surface area of the tissue Solubility of the gas Partial pressure gradient
Inversely proportional to the Thickness of the tissue
Fickrsquos Law
Figure 4-8
C Properties of Gases
4 Gas Pressure All gases exert pressure Gas pressure in a liquid is known as gas
ldquotensionrdquo Atmospheric pressure is measured with a
barometer Pressure the force that a gas exerts over a
given area P = ForceArea lbin2
C Properties of Gases
4 Gas Pressure Atmospheric Pressure The pressure that
the atmospheric gases exert on objects within the Earthrsquos atmosphere
Gases that make up the atmosphere are attracted to the Earthrsquos surface by gravity
Highest near the Earthrsquos surface Sea level
760 mmHg Denver 1 mile above sea level
630 mmHg
112
Atmospheric Pressure
Measured with a barometer
Evangelista Torricelli The mercury barometer
uses the weight of a column of mercury to equilibrate with the force of the gas molecules hitting the surface of a mercury reservoir
