Question

Which of the following would increase diffusion of a gas across the alveolar/pulmonary capillary membrane?

Select one:

a. An increase in thickness of the membrane

b. A decrease in surfactant

c. An increase in the time that blood is in the alveolar capillaries

d. A decrease in the partial pressure gradient

e. An increase in the thickness of the mucous layer lining the alveoli

Answer 1

Correct answer is option C.

Explanation- when blood stays more in the alveolar capillaries, then more time the respiratory gases will have to diffuse from alveoli to blood. Hence, diffusion of gases is directly proportional to the time the blood stays in capillaries.

Other factor on which diffusion depends-

1. Pressure gradient- diffusion capacity is directly proportional to pressure gradient. Hence option d is incorrect.

2. Solubility of gas in fluid- diffusion capacity is directly proportional to solubility of gas

3. Directly proportional to total surface area respiratory membrane.

4. Inversely proportional to molecular weight of gas

5. Inversely proportional to thickess of respiratory membrane. Hence option a is incorrect.

6. Surfactant increases diffusion because surfactant protects alveoli from collapsing.