Gas diffusion

Question 1

T/F

CO2 is ~20x more soluble than O2

Answer 1

true

Question 2

Factors that determine rate of diffusion

Answer 2

1. barrier thickness (primary clinical problem)
2. partial pressure gradient
3. SA for gas diffusion
4. gas solubility

Question 3

formula for rate of diffusion

(no need to memorize)

Answer 3

Question 4

alveolar gas that cannot diffuse least readily

Answer 4

nitrogen

Question 5

alveolar gas that diffuse most readily

Answer 5

co2

Question 6

When diffusion is impaired, which gas is the least soluble

Answer 6

o2

Question 7

membrane thickness when there’s inflammation?

Answer 7

increase

Question 8

membrane thickness when there’s edema

Answer 8

increase; fluid accumulates btw epithelium and capillaries

Question 9

membrane thickness when there’s fibrosis

Answer 9

increase

Question 10

surface area when there’s chest pain?

Answer 10

decrease; shallower breathing → fewer alveoli fully expanded

Question 11

surface area when there’s obesity

Answer 11

decrease; reduced chest wall compliance

Question 12

Does diffusion impairment alone usually cause CO₂ retention?

Answer 12

no; hypercapnia needs multiple factors

Question 13

How does diffusion impairment affect alveolar gases overall?

Answer 13

decrease in PaO2
PaCO2 is normal or mildly increases

Question 14

AaDO2 normal in

Answer 14

low PiO2
alveolar hypoventilation

Question 15

AaDO2 increases in

Answer 15

diffusion impairment
V/Q mismatch
R to L shunt

Question 16

PAO2 is always greater than PaO2?

Answer 16

YES

Question 17

PaO2 when there’s impaired diffusion

Answer 17

decrease

Question 18

SO2 when there’s impaired diffusion

Answer 18

decrease

Question 19

AaDO2 when there’s impaired diffusion

Answer 19

increase

Question 20

Why is PaCO₂ often normal in diffusion impairment?

Answer 20

much more soluble than O2

Question 21

with supplemental O2, PaO2 rises above

Answer 21

> 50 mmHg

Question 22

PaO2 in alveolar hypoventilation

Answer 22

decrease

Question 23

SO2 in alveolar hypoventilation

Answer 23

decrease

Question 24

PaCO2 in alveolar hypoventilation

Answer 24

increase

Question 25

pH in in alveolar hypoventilation

Answer 25

decrease

Question 26

HCO3- in alveolar hypoventilation

Answer 26

increase

Question 27

T/F Diffusion impairment is not the most common cause of hypoxemia

Answer 27

true

Question 28

A history of no symptoms at rest and dyspnea induced by light exercise is suggestive of which cause of hypoxemia?

Answer 28

diffusion impairment

Question 29

T/F Diffusion abnormalities impair the diffusion of O2 more than they impair the diffusion of CO2

Answer 29

true

Question 30

Under normal conditions O2 and CO2 both equilibrate across the alveolar septa before blood traverses half the alveolar capillary

Answer 30

true

Question 31

What happens to PaCO₂ during compensatory hyperventilation?

Answer 31

↓

Question 32

hyperventilation happens to compensate which causes of hypoxemia?

Answer 32

low PiO2 diffusion impairment low V/Q mismatch R-L shunt

Question 33

How do patients usually increase ventilation during compensation?

Answer 33

increasing Vₜ more than respiratory rate f

Question 34

What conditions impair compensatory hyperventilation?

Answer 34

stiff lungs obesity

Question 35

T/F Under normal conditions O2 and CO2 both equilibrate across the alveolar septa before blood traverses half the alveolar capillary

Answer 35

trueee

Question 36

T/F hypoxemia causes compensatory hyperventilation

Answer 36

true