Hypercarbia and Hypoxemia11.7.11

What happens to our cells if we don’t get enough O2?

What happens to our cells if we don’t get enough O2?

Cannot make ATP

What happens to our cells if we don’t remove CO2?

What happens to our cells if we don’t remove CO2?

CO2 is not bad by itself but can combine with H2O in the blood makes carbonic acid change in pH can cause structure changes in proteins if 3D structure can lead to loss in function.

tissue

CIRCULATION

CO2 O2

PIO2 = 150 mmHgPICO2 = 0.3 mmHg (0)

PaO

2 =

98

mm

Hg

PaC

O2

= 4

0 m

mH

g

CO2 O2

PvO

2 =

40

mm

Hg

PvC

O2

= 4

5 m

mH

g

PAO2 = 100 mmHgPACO2 = 40 mmHg

Subscripts:I = inhaledA = alveolara = arterialv = venous

Why is PIO2 150 mmHg if atmospheric PO2 is 160 mmHg?

tissue

CIRCULATION

CO2 O2

PIO2 = 150 mmHgPICO2 = 0.3 mmHg (0)

PaO

2 =

98

mm

Hg

PaC

O2

= 4

0 m

mH

g

CO2 O2

PvO

2 =

40

mm

Hg

PvC

O2

= 4

5 m

mH

g

PAO2 = 100 mmHgPACO2 = 40 mmHg

Subscripts:I = inhaledA = alveolara = arterialv = venous

Why is PIO2 150 mmHg if atmospheric PO2 is 160 mmHg?

Saturation with H2O in the lung space decreases the PO2

Causes of Hypoxemia

1.

2.

3.

4.

Causes of Hypoxemia

1. Diffusion Impairment

2. V/Q Abnormalities

3. Shunt

4. Hypoventilation

Diffusion impairment

PAO2

PcapO2

T

A

.VO2 = K x A x (PAO2 – PaO2)/T

Diffusion impairment .VO2 = K x A x (PAO2 – PcapO2)/T

How does the rate of transport change with:

-Increased thickness, ie. with fibrosis?

-Decreased surface area, ie pneumonia?

-Decreased PcapO2, less O2 in the capillary blood?

Diffusion impairment .VO2 = K x A x (PAO2 – PcapO2)/T

How does the rate of transport change with:

-Increased thickness, ie. with fibrosis?

Slow-Decreased surface area, ie pneumonia?

Slow-Decreased PcapO2, less O2 in the capillary blood?

fast, increased diffusion

V/Q Abnormalities

0Upper parts of the lung receive more/less blood supply than the lower parts (gravity).

0Upper parts of the lung also receive more/ less of the tidal volume.

V/Q Abnormalities

0Upper parts of the lung receive more/less blood supply than the lower parts (gravity).

0Upper parts of the lung also receive more/ less of the tidal volume.

V/Q Abnormalities

0The result is that the upper parts of the lung receive relatively more/less ventilation than they do blood flow, while the lower parts of the lung receive relatively more/less ventilation than they do blood flow.

V/Q Abnormalities

0The result is that the upper parts of the lung receive relatively more/less ventilation than they do blood flow, while the lower parts of the lung receive relatively more/less ventilation than they do blood flow.

Shunt

Definition:

Let’s take a short cut! But is it a good short cut?

Shunt

Definition:

When blood passes from the right heart to the left heart without becoming oxygenated?

ShuntWhich causes blood to go from the right to left heart without going through the lungs?

A. Foreign object (ie. Peanut)B. Bronchial circulationC. Pneumonia or abundant pusD. Foramen Ovale

ShuntWhich causes blood to go from the right to left heart without going through the lungs?

A. Foreign object (ie. Peanut)B. Bronchial circulationC. Pneumonia or abundant pusD. Foramen Ovale

ShuntBronchial circulation- only goes through the larger airways and does not reach the alveolar region

Foramen Ovale- system established in utero that may not close when the baby is born

Shunt

What happens with these two?

Foreign object (ie. Peanut)Pneumonia or abundant pus

Shunt

What happens with these two?Foreign object (ie. Peanut)

Pneumonia or abundant pus

Blood goes through the lungs but does not come into contact with the gas exchange region.

Does hypoventilation cause hypoxemia or hypercarbia?

Does hypoventilation cause hypoxemia or hypercarbia?

BOTH!!

Hypoventilation

What things can cause hypoventilations?1.

2.

3.

4.

Hypoventilation

What things can cause hypoventilations?1. Problems with nerves

2. Problems with muscles

3. Drugs that suppress resp. drive (morphine)

4. Problems with central resp. drive (CCHS, Ondine’s)

Hypercarbia

In addition to hypoventilation,

Think ALVEOLAR VENTILATIONThink DEAD SPACE

How to calculate alveolar ventilation?

How to calculate alveolar ventilation?

VA = (VT V‑ D) x f

What happens when you increase dead space?

VA = (VT V‑ D) x f

What happens when you increase dead space?

VA = (VT V‑ D) x f

Incr. dead space decrease alveolar ventilation increase PaCO2 = hypercarbia if above 40 mmHg

Dead Space

Name 3 things that cause changes in dead space.

Equipment

-Snorkel-Gas Mask-Ventilator

Deep Vein Thrombosis

How does DVT cause dead space?

Deep Vein Thrombosis

How does DVT cause dead space?Sedentary blood clot travels to lung embolus creates dead space decreased gas exchange air in and out is unchanged

Air can get in but gas exchange surface is destroyed.