If a lung having a normal ventilation-perfusion ratio (=1) SUDDENLY develops ventilation-perfusion ratio <1, which...

If a lung having a normal ventilation-perfusion ratio (=1) SUDDENLY develops ventilation-perfusion ratio <1, which of the following will occur? Explain

A decrease in arterial pO₂

An increase in alveolar pO₂

A decrease in cardiac output

A decrease in arterial pCO₂

Solutions

Expert Solution

The determination of alveolar ventilation to perfusion ratio involves two assumptions. One, that ventilation occurs equally in all alveoli. And second, that blood flow through all capillaries is uniform.
Now, if ventilation perfusion ratio drops below 1, then, the amount of perfusion occuring is greater than amount of ventilation. This implies, alveolar air concentration of different gases will gradually start to move towards to the concentration of gases in blood. Therefore, the partial pressure of carbon dioxide will increase in alveolar air and that of oxygen will decrease.
However, the concentration gradient that was present between arterial blood and alveolar air now slowly starts to diminish. As a result, the diffusion of gases slows down. This results in accumulation of these gases in blood. The partial pressure of oxygen in blood decreases and the partial pressure of carbon dioxide increases.
So, option A is correct.

Sydney Mullin answered 1 year ago

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