Alveolar Gas Exchange MCQ Quiz | Respiratory System

1. What is the approximate partial pressure of oxygen (PO2) in the alveolar air of a healthy individual at sea level?

2. According to Fick’s law of diffusion, which of the following changes would DECREASE the rate of gas exchange across the alveolar-capillary membrane?

3. The exchange of which gas across the respiratory membrane is typically considered “perfusion-limited” under normal physiological conditions?

4. A pulmonary embolism would most likely result in which of the following?

5. What is the primary reason that carbon dioxide (CO2) diffuses across the alveolar-capillary membrane about 20 times more rapidly than oxygen (O2)?

6. In a lung region with a V/Q ratio of 0 (a shunt), the composition of blood leaving the capillaries will most closely resemble:

7. The diffusing capacity of the lung for carbon monoxide (DLCO) is used clinically to assess:

8. Which condition would lead to an A-a (Alveolar-arterial) gradient that is significantly increased above the normal range of 5-10 mmHg?

9. In a standing individual, where is the ventilation-perfusion (V/Q) ratio typically the highest?

10. The time a red blood cell spends in the pulmonary capillaries (pulmonary transit time) at rest is approximately:

11. A patient with emphysema has destruction of alveolar walls. This primarily impairs gas exchange by:

12. Which law states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid?

13. The partial pressure of CO2 (PCO2) in mixed venous blood returning to the lungs is approximately:

14. What effect does strenuous exercise have on the pulmonary transit time and gas exchange?

15. In a region of the lung with alveolar dead space (V/Q ratio approaching infinity), the gas composition of the alveoli will most closely resemble:

16. Pulmonary edema primarily impairs gas exchange by:

17. Under normal conditions, how long does it take for pulmonary capillary blood PO2 to equilibrate with alveolar PO2?

18. Why is carbon monoxide (CO) an ideal gas for measuring diffusing capacity?

19. The PO2 of systemic arterial blood is slightly lower than alveolar PO2 (approx. 95 mmHg vs 104 mmHg) mainly due to:

20. Which of the following components is NOT part of the respiratory membrane (blood-gas barrier)?

21. At the apex of the upright lung, which of the following relationships is generally true?

22. The partial pressure of water vapor (PH2O) in the humidified tracheal air is constant at body temperature and is equal to:

23. In a patient with hypoventilation, what changes would you expect in arterial blood gases?

24. The difference between alveolar ventilation (VA) and minute ventilation (VE) is accounted for by:

25. A patient is given 100% oxygen to breathe. Which of the following causes of hypoxemia will show the LEAST improvement?