Ventilation/Perfusion Matching and Hypoxemia

Question 1

The ventilation perfusion ratio is higher or lower in the apex of the lung (zone 1)?

Answer 1

higher in the apex of the lung in an upright individual than it is in the base of the lung (zone 3)

Question 2

T/F. Alveoli in the base are more compliant meaning there is more ventilation in this region than the apex.

Answer 2

true

Question 3

There is more BF to the base of the lung compared to the apex. Why?

Answer 3

since intravascular pressure in the arteries is higher

Question 4

Describe Va/Q at the base of the lung along with:

PCO2
PO2
pH

Answer 4

Va/q < 1.0

PCO2 > 40
PO2 < 100
pH < 7.4

Question 5

What is the Va/Q for the apex of the lung?

PCO2
PO2
pH

Answer 5

Va/Q = >1.0
PO2 = > 100
PCO2 = < 40
pH > 7.4

Question 6

If ventilation is 0 but there is blood flow, then VA/Q = 0.

What does this mean?

Answer 6

right to left shunt and the blood gases leaving the alveoli are the same as venous blood (low PO2 and high PCO2; y-axis intercept

Question 7

If blood flow is zero but there is ventilation what is this called?

Answer 7

alveolar dead space VA/Q= infinity

Question 8

VA/Q for 2 lung units below:

A= 0.62
B= 0.73

Which lung had the greatest:

1. PACO2, end capillary PCO2
2. PAO2, end capillary PO2
3. end capillary pH

Answer 8

Answer A
Answer B
Answer B

Question 9

Diffusion problems of the lungs typically occur in what conditions?

Answer 9

fibrosis, asbestosis, and sarcoidosis

Question 10

PaO2 is less than, greater than or equal to PAO2 in lungs where there is marked diffusion impairment?

Answer 10

less than

Question 11

What are some conditions that can cause a VA/Q mismatch?

Answer 11

severe obstruction (status asthmaticus, cystic fibrosis, anaphylaxis, infection (pneumonia), partial occlusion of an airway

Question 12

What is an intrapulmonary shunt?

Answer 12

when systemic venous blood is delivered to the left side of the heart without exchanging O2 and CO2 with the alveoli rt to left shunt

Question 13

What are some conditions that can cause intrapulmonary shunts?

Answer 13

atelactatic lung regions (pneumothorax, ARDS), complete occlusion of an airway (mucus plug, foreign body), and the rt to left shunts created by heart defects (tetralogy of Fallot)

Question 14

The failure to obtain a significant increase in arterial PO2 following the administration of supplemental O2 in hypoxemia is strong evidence of what?

Answer 14

a shunt