As altitude increases, what happens to the partial pressure of oxygen?

As altitude increases, the partial pressure of oxygen decreases. This is primarily due to the reduction in atmospheric pressure that occurs at higher altitudes. The total atmospheric pressure at sea level is approximately 760 mmHg, and as you ascend, this pressure diminishes. The partial pressure of any gas, including oxygen, is a fraction of the total atmospheric pressure based on its concentration.

Oxygen makes up about 21% of the atmosphere by volume, so as the total pressure decreases at higher altitudes, the partial pressure of oxygen also decreases proportionally. This decline in partial pressure can lead to several physiological effects, such as diminished oxygen availability for breathing, which is a critical consideration for aviation and high-altitude activities. Thus, understanding this concept is essential for aeromedical assessments and ensuring pilot and passenger safety in varied altitudes.