Question

The partial pressure of inspired oxygen (PO2) decreases with increasing altitude because of the

a. lower percent of oxygen in the air.
b. lower barometric pressure.
c. higher percent of carbon dioxide in the air.
d. higher percent of nitrogen in the air.

Answer 1

The partial pressure of inspired oxygen decreases with increasing altitude primarily due to the lower barometric pressure. This makes it more difficult for the body to achieve the same level of oxygen saturation at high altitudes compared to sea level.

Step-by-step explanation:

The partial pressure of inspired oxygen (PO2) decreases with increasing altitude primarily due to the lower barometric pressure. As altitude increases, the atmospheric pressure decreases, which affects the concentration of gases in the air. Although the percentage of oxygen in the air remains constant at 21%, the lower atmospheric pressure results in a decrease in the partial pressure of oxygen.

This decrease in partial pressure makes it more difficult for the body to achieve the same level of oxygen saturation at high altitudes compared to sea level. Hemoglobin saturation, which represents the binding of oxygen to hemoglobin molecules in the blood, is lower at high altitudes. For example, at 19,000 feet above sea level, hemoglobin saturation is about 67%, compared to about 98% at sea level.

It's important to note that the percent of oxygen in the air does not change significantly with increasing altitude. The decrease in partial pressure of oxygen is primarily caused by the lower barometric pressure.