Deck 7: Gas Diffusion

Question 1

What is the mean DLCOsb range for healthy adults?

A) 20 to 30 mL/min/mm Hg
B) 30 to 40 mL/min/mm Hg
C) 40 to 50 mL/min/mm Hg
D) 50 to 60 mL/min/mm Hg

Answer 1

20 to 30 mL/min/mm Hg

Question 2

Why is CO the ideal gas for measuring the extent to which the alveolar capillary membrane itself impedes the diffusion rate?

A) Blood can absorb CO at a greater rate than CO can diffuse across the alveolar capillary membrane.
B) CO is lighter than O₂.
C) CO can diffuse across the alveolar capillary membrane faster than blood can absorb it.
D) CO is heavier than O₂.

Answer 2

Blood can absorb CO at a greater rate than CO can diffuse across the alveolar capillary membrane.

Question 3

When are patients with thickened alveolar capillary membranes most likely to show evidence of oxygen diffusion impairment?

A) In supine position
B) In prone position
C) During exercise
D) In any position at rest

Answer 3

During exercise

Question 4

CO₂ is how many times more soluble than O₂?

A) 16
B) 20
C) 24
D) 28

Question 5

How many times faster does oxygen diffuse through a gas medium than CO₂?

A) 0.9
B) 1.0
C) 1.1
D) 1.2

Question 6

Diffusion of which of the following gases will be limited by a defective alveolar capillary membrane?

A) O₂
B) CO₂
C) NO₂
D) N₂O

Question 7

Which of the following statements apply to Fick's law?
I.Gas diffusion increases with increased membrane surface area.
II.Gas diffusion increases with decreased membrane surface area.
III.Gas diffusion increases with increased pressure gradient.
IV.Gas diffusion decreases if membrane thickness increases.

A) I, III, IV
B) I, II, III, IV
C) II, IV
D) II, III, IV

Question 8

If oxygen equilibrium between the alveolus and capillary never occurs because of thickened membranes, oxygen transfer is truly:

A) Perfusion limited
B) Diffusion limited
C) Concentration limited
D) Perfusion and diffusion limited

Question 9

Which of the following are components of the diffusion path?
I.Capillary endothelium
II.Intracellular fluid bathing the hemoglobin molecule
III.Red blood cell membrane
IV.Alveolar epithelium
V.Surfactant layer lining the alveolar surface

A) I, II, III, IV
B) II, III
C) I, II, III, IV, V
D) II, III, IV

Question 10

What is the PAO₂ of a person breathing room air at sea level, with a PaCO₂ equal to 40 mm Hg and an R equal to 0.8?

A) Approximately 80 mm Hg
B) Approximately 90 mm Hg
C) Approximately 100 mm Hg
D) Approximately 110 mm Hg

Question 11

For a person breathing 21% oxygen, what is the inspired oxygen partial pressure?

A) Approximately 80 mm Hg
B) Approximately 100 mm Hg
C) Approximately 140 mm Hg
D) Approximately 160 mm Hg

Question 12

Why is N₂O the ideal gas for measuring the extent to which pulmonary blood contributes to the diffusion rate?

A) Blood can absorb N₂O at a greater rate than N₂O can diffuse across the alveolar capillary membrane.
B) If N₂O is inhaled, the pulmonary capillary blood reaches its maximum capacity for N₂O almost instantly.
C) If N₂O is inhaled, the pulmonary capillary blood reaches its maximum capacity for N₂O slowly.
D) Blood can absorb N₂O at a slower rate than N₂O can diffuse across the alveolar capillary membrane.

Question 13

What is the most common cause of resting hypoxemia?

A) A mismatch between ventilation and diffusion
B) A mismatch between ventilation and permeability
C) A mismatch between ventilation and dead space
D) A mismatch between ventilation and blood flow

Question 14

Which of the following laws states that the amount of gas dissolving in a liquid is directly proportional to the gas partial pressure?

A) Boyle's law
B) Charles' law
C) Henry's law
D) Reynold's law

Question 15

Which of the following is the main limiting factor for the oxygen transfer rate?

A) Perfusion
B) Diffusion
C) Solubility
D) Molecular weight of the gas

Question 16

Combining Graham's law and Henry's law, how many times faster does carbon dioxide diffuse across the alveolar capillary membrane than oxygen?

A) 10
B) 20
C) 30
D) 40

Question 17

The rate of gas diffusion in the lung is inversely proportional to its molecular weight and directly proportional to which of the following physical properties?

A) Density
B) Solubility
C) Specific gravity
D) Proton concentration

Question 18

Which of the following are true of the respiratory exchange ratio?
I.It is the ratio of alveolar CO₂ excretion to blood oxygen uptake.
II.R = VCO₂/VO₂
III.It is the ratio of oxygen uptake to blood alveolar CO₂ excretion.
IV.Its value is normally approximately 0.8.

A) I, II, IV
B) III, IV
C) I, II, III, IV
D) II, IV

Question 19

How do you obtain the diffusion capacity for oxygen?

A) It is obtained by multiplying D_LCO_sb by 1.23.
B) It is obtained by multiplying D_LCO_sb by 24.
C) It is obtained by dividing D_LCO_sb by 1.23.
D) It is obtained by dividing D_LCO_sb by 24.

Question 20

Which of the following conditions can increase the length of the diffusion path?
I.Fibrotic thickening of alveolar and capillary walls
II.Fluid in the alveoli
III.Interstitial edema fluid
IV.Capillary vasoconstriction

A) I, II, III
B) II, III
C) I, II, III, IV
D) II, III, IV

Question 21

Which of the following conditions has an inverse relationship with D_LCO_sb?

A) Age
B) Exercise
C) Lung volumes
D) PAO₂

Question 22

What is the best explanation for the D_LO₂ being greater than the D_LCO_sb?

A) O₂ is less soluble than CO in the alveolar capillary membrane but more soluble in the plasma and therefore diffuses more rapidly.
B) O₂ is more soluble than CO in the alveolar capillary membrane and less soluble in the plasma and therefore diffuses more rapidly.
C) O₂ is less soluble than CO in the alveolar capillary membrane and the plasma and therefore diffuses more rapidly.
D) O₂ is more soluble than CO in the alveolar capillary membrane and the plasma and therefore diffuses more rapidly.

Question 23

The D_LCO_sb is useful in differentiating emphysema from what other obstructive disease?

A) Asthma
B) Pneumonia
C) ARDS
D) Bronchiectasis