Gas Exchange and Hypoxemia

Question 1

Respiratory membrane

Answer 1

The wall of the alveoli, the interstitium, and the wall of the capillary

Question 2

How does CO2 influence bicarbonate serum levels?

Answer 2

More CO2 absorbed = higher serum bicarb levels

Question 3

3 ways CO2 is transported

Answer 3

As bicarb (70%)
Bound to hemoglobin (23%)
Diffused in plasma (7%)

Question 4

Haldane effect

Answer 4

Oxygenated Hb less able to pick up CO2

Question 5

Partial pressure of
1. O2
2. CO2
leaving and entering the lung

Answer 5

1. 100mmHg, 40 mmHg

2. 40 mmHg, 47 mmHg

Question 6

Dead space alveolus

Answer 6

Blocked capillary
V/Q = infinity
Still completely ventilated

Question 7

Shunt alveolus

Answer 7

No fresh gas is delivered to blood (blocked airway)

V/Q = 0

Question 8

Effect of
1. Fraction of O2
2. Arterial CO2
on PAO2

Answer 8

1. High fraction = increased PAO2

2. High PaCO2 = low PAO2

Question 9

Hemoglobin saturation values when PaO2 is at

1. 40
2. 60
3. 90

Answer 9

1. 60%
2. 90%
3. 97%

Question 10

Most clinically important cause of hypoxemia

Answer 10

VQ mistmatch

Seen in pneumonia, heart failure, pulmonary emboli

Question 11

5 causes of hypoexmia (in order of commonality)

Answer 11

1. VQ mismatch
2. Hypoventilation
3. Right-to-left shunt
4. Thickened diffusion barrier
5. Low inspired ppO2

Question 12

Hypoxemia is when PaO2 drops to…

Answer 12

Under 60 mmHg