hyperbaric oxygen therapy module ii crc 432 subacute cardiorespiratory care problem-based learning

Hyperbaric Oxygen TherapyModule II

CRC 432 Subacute Cardiorespiratory

CareProblem-Based Learning

HBO OUTLINE

• Definitions• History• Altitude/descent• Gas laws• Physiological effects of HBO

Hyperbaric Oxygen Therapy

• Therapeutic oxygen at pressures greater than 1 atm

• Unit expressing HBO pressure = ata• Ata = atmospheric pressure absolute• 1 ata = 1 atmosphere (atm), or 760

torr• HBO general pressure range = 2 to 3

ata


• Pressure:pressure = force/area

• Force:force = mass x

acceleration


• Ambient pressure = surrounding pressure on land, or under water.

• Atmospheric pressure = surrounding pressure caused by the weight of air.

• Water pressure = surrounding pressure caused by weight of water.


• Barometric pressure = measure of atmospheric pressure

• Barometric pressure = atmospheric pressure

• When surrounded by air: atmospheric pressure = ambient pressure = barometric pressure


• When surrounded by water: atmospheric pressure = water pressure = ambient pressure

• CAUTION!!! Don’t confuse: atmospheric pressure & atmosphere as unit


• Atmospheric pressure can be ANY value:

1 atm (sea level)½ atm (8,000 feet

elevation)3 atm (hyperbaric

chamber)


ABSOLUTE PRESSURE vs. GAUGE PRESSURE

• 33 ft sea water = 1 atm• Gauges set sea level pressure at 0 • At 33 ft depth, gauge indicates 1 atm• Absolute pressure = 2 atm


• Standard atmospheric pressure: average sea level pressure

• 14.7 psi• 1034 cm H2O• 101.3 kPa• 760 mm Hg (torr)• 33 ft H2O• 29.9 in Hg


• First sealed chamber called Domicilium built in 1662

• Chamber held compressed air (21% O2)

• Treated various ailments: scurvy, arthritis, inflammation, rickets

• Likely too little compression to benefit patients

Hyperbaric Oxygen Therapy• Beddoes is known as the “Father of

Respiratory Therapy”• Thomas Beddoes founded the “Pneumatic

Institute in Bristol,” England 1780• Patients inhaled different gases to treat

their diseases

• Pneumatic laboratory enriched with O2 treated chronic conditions

• Father of English poet Thomas Lovell Beddoes


• J. Priestly discovered O2 in England 1776

• Antoinne Lavoisier of France shares O2 discovery


GAS LAWSAir under hyperbaric conditions obeys

the same gas laws as air in the atmosphere.

Boyle’s law (1627 – 1691)Dalton’s law (1766 – 1844)Henry’s law (1774 – 1790)


Boyles’s law

• When mass & T are K, V & P inverse.K = V x PK = 2V x ½PK = ½V x 2 P

• If P increases, V decreases, & vice versa.


Boyle’s law• When mass & T are K, D & P direct.

K = D/P• Consider container open at one end

holding 1 L at 1 atm.• At 2 atm, V by ½, & D doubles.• At 3 atm, V by ⅓, & D triples.


Boyle’s law

• During HBO, density in lungs increases.

• Deep scuba diving: density of air increases, & breathing becomes more difficult.


Dalton’s law

• PT = pressure exerted by gas equals the sum of all the Pgas of the constituent gases.

PT = P1 + P2 + P3 = . . . Pn


Dalton’s law To calculate the partial pressure of

a gas in a mixture of gases:

Pgas = Fgas (PT – PH2O)

Hyperbaric Oxygen TherapyDalton’s law

TRUE or FALSEThe sum of the partial pressures of all the gases in a gas mixture can never exceed the total pressure of the gas mixture.

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?


Dalton’s law

TRUE!!!

Hyperbaric Oxygen TherapyDalton’s law

TRUE or FALSEAs air pressure increases (hyperbarism) or decreases (altitude), the partial pressures exerted by the constituent gases increases or decreases, as well.

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Dalton’s law

TRUE!!!


Dalton’s law TRUE or FALSE

When room air is compressed in a hyperbaric chamber, the percentage of the individual gases in the mixture is the same.

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Dalton’s law

TRUE!!!


Hyperbaric Oxygen TherapyDalton’s law• Lower partial pressures at altitude reflect

presence of less O2 & N2 molecules per volume compared to sea level.

• Summit at Mt. Everest (29,000 ft): 21% O2, 78% N2, 1% other

• # of O2 & N2 molecules per volume of air only 1/3 that at sea level.

• PO2 & PN2 only 1/3 that at sea level


Henry’s lawAmount of gas that dissolves in a liquid at a given temperature is a function of the partial pressure of the gas in contact with the liquid, and the solubility of the gas in that particular liquid.


Henry’s law

SIMPLIFIED: As the partial pressure of a gas above the surface of a liquid increases, more of that gas will dissolve into that liquid.


Henry’s & Dalton’s laws

When ambient pressure decreases (altitude), the partial pressures of O2 & N2 in the body fall, and fewer O2 & N2 molecules dissolve into the blood.


Henry’s & Dalton’s laws

When ambient pressure increases (hyperbarism), the partial pressures of O2 & N2 in the body increase, and more O2 & N2 molecules dissolve into the blood.


Physiologic Effects• Hyperoxygenation

– Increases volume of O2 in plasma

– 10 to 13 x greater than normal

– Elevated O2 levels purge toxins & CO from the body



– At sea level while breathing room air plasma O2 concentration is 0.3 vol%

100 torr x 0.003 vol%/torr = 0.3 vol%


Physiologic Effects• HyperoxygenationAlveolar Air Equation:

R

OF0.1OFPaCO)PP(OFOP 2

222T22

IIOHIAP O F O (P P ) P aC O F O

1 .0 F O

RA I H O I

I2 2 T 2 2 2

2

P O F O (P P ) P aC O F O

1 .0 F O

RA I H O I

I2 2 T 2 2 2

2



HBO patient breathing FIO2 0.4@ 2.5 atm

P O 0 .4 (1 ,9 0 0 to rr 4 7 to rr) 4 0 to rr 0 .4 1 .0 0 .4

0 .8A 2

P O 0 .4 (1 ,9 0 0 to rr 4 7 to rr) 4 0 to rr 0 .4

1 .0 0 .4

0 .8A 2


Hyperoxygenation

PAO2 = 1,807 torr 1,807 torr x 0.003 vol%/torr = 5.4 vol%

PAO2 = 0.4 (1,900 torr – 47 torr) – 40 torr(1.15)


Normal a-v difference = 5.0 vol%

Arterial Blood

PaO2 100 torr

SaO2 97.5%

[Hb] 15 g%

Mixed Venous Blood

PvO2 46 torr

SvO2 73%

[Hb] 15 g%


CaO2 = (1.34)(15) (0.975) + 100(0.003)

= 19.6 vol%

CvO2 = (1.34)(15)(0.73) + 46(0.003 vol%.torr)

= 14.6 vol%

CaO2 – CvO2 = a-v diff = 5.0 vol%


PHYSIOLOGIC EFFECTS• Hyperoxygenation

– HBO increases dissolved oxygen in the plasma


Physiologic Effects• Direct Pressure

– Shrinks gas bubbles (Boyle’s law) to expedite reabsorption of gases

– Good for decompression sickness (DCS – aka: “the bends”)

– Good for air/gas embolism


Physiologic Effects• Vasoconstriction

– Reduces blood flow

– No significant reduction in tissue O2nation

– Benefits crushing type injuries– Benefits thermal burns

– O2 directly enters interstitial fluid promoting healing


Physiologic Effects• Bactericidal/Bacteriostatic

– Halts spread of toxins– Enhances killing of bacteria– Stimulates production of neutrophils


Physiologic Effects• Angiogenesis/Neovascularization

– Promote growth of new blood vessels– Promote collagen formation to

support new blood vessels


• Atmospheric pressure caused by weight of gas molecules in contact with earth’s surface

• Atmospheric pressure exerted on a surface of water

• Pressure decreases with altitude• Denver, CO at 5,280 ft elevation; 1

atm = 630 torr

Hyperbaric Oxygen Therapy• Water more dense than air• 33 ft sea water = 1 atm (760 torr)• Pressure at any depth = hydrostatic

pressures + atm pressure• Depth of 33 ft of H2O = 2 atm, or 2 ata• At 33 ft H2O, 2,112 lbs over each ft2 of

body (33 ft x 64 lbs/ft3 = 2,112 lbs/ft2)• 66 ft H2O = 3 ata


• Indications – CHRONIC– Nonhealing wounds– Refractory osteomyelitis– Radiation necrosis

www.uhms.org/indications/indications.htm


• Hazards– Fire: 50 deaths worldwide in 20 years

(1997)• Most common FATAL complication• Only 100% cotton fabrics in chambers• No alcohol/petroleum products• No sprays, makeup, deodorant

– Barotrauma• Ear/sinus trauma• Tympanic membrane rupture• pneumothorax


• Hazards– O2 Toxicity

•CNS toxicity (twitching, seizures, convulsions)

•Pulmonary toxicity (leaky A/C membrane)

– Other•Sudden decompression•Reversible visual changes•Claustrophobia


• Hyperbaric Chambers– Monoplace transparent Plexiglas

cylinder– One patient– No mask– No electric equipment inside– 100% oxygen– Less expensive than multi-place


multiplacehyperchamber.jpg

• Multi-place chambers– large tanks able to accommodate 2 – 14

people– achieve pressures up to 6 atm– have a chamber lock entry system that allows

medical personnel to pass through without altering the pressure of the inner chamber

– allows patients to be directly cared for by staff– filled with compressed air; patients breathe

100% oxygen through facemask, head hood, or endotracheal tube.


img_header.jpg

multiplacehyperchamber.jpg


COHb% SYMPTOMS

≤ 10% Usually none

10-20% Mild headache, dyspnea

20-30% Throbbing headache, impaired concentration

30-40% Severe headache, impaired thinking

40-50% Confusion, lethargy , syncope

50-60% Respiratory failure, seizures

60-70% Coma, convulsions, depressed cardiac & respiratory function

≥ 70% Coma, rapidly fatal

hyperbaric oxygen therapy module ii crc 432 subacute cardiorespiratory care problem-based learning

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