The partial pressure of oxygen in the alveolar gas is affect

The partial pressure of oxygen in the alveolar gas is affected by certain situations. Classify each of the following conditions as causing an increase, decrease, or no change in alveolar PO_2.

Solution

Increase in pO2 will occur due to

Increased alveolar ventilation and unchanged metabolism

Decreased metabolism and unchanged alveolar ventilation.

Decreased pO2 will occur due to

Decreased alveolar ventilation and unchanged metabolism

Increased metabolism and unchanged alveolar ventilation

Breathing air with low pO2

No change in pO2 will occur due to

Proportional increase in metabolism and alveolar ventilation

Remember that, metabolism requires oxygen so it lowers partial pressure of oxygen whereas alveolar ventilation always increase pO2.