Cardiopulmonary Anatomy & Physiolo...

7th Edition
Des Jardins + 1 other
ISBN: 9781337794909



Cardiopulmonary Anatomy & Physiolo...

7th Edition
Des Jardins + 1 other
ISBN: 9781337794909
Textbook Problem

During exercise, the P ( A=a ) O 2 begins to increase when the oxygen consumption reaches about what percent of its maximum?

A. 10 percent

B. 20 percent

C. 30 percent

D. 40 percent

Summary Introduction


The pressure of oxygen in the alveoli and arteries plays a major role during exercise. The difference in pressure indicates the greater respiratory efforts with respect to the level of oxygenation that is to be achieved. The P(A-a)O2 increases with a defect in perfusion, shunting, and diffusion.


Explanation for the correct answer:

Option (D) states that the P(A-a)O2 increases when the body consumes oxygen around 40% of its maximum at the time of heavy exercise. P(A-a)O2 stands for the difference in the pressure of oxygen in the alveoli to that of the arteries. The P(A-a)O2 is the measure of effective working of the lungs of transporting oxygen into the blood. The difference in the mean alveolar–arterial oxygen tension occurs during exercise due to mismatched perfusion, ventilation, and blood shunting between the right and left pulmonary capillaries. Hence, option (D) is the correct answer.

Explanation for the incorrect answer:

Option (A) states that P(A-a)O2 increases during exercise, when the consumption of oxygen elevates to 10% of its maximum. The P(A-a)O2 increases when oxygen diffusion is defective. This is because individual tries harder to breathe and achieve normal oxygenation. So, it is an incorrect option.

Option (B) states that when the usage of the oxygen reaches 20% of the maximum oxygen consumption, the P(A-a)O2 starts to increase at the time of very heavy exercise

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