American Airlines (AA) Medical KSV Practice Test

In flight, the cabin is pressurized to an altitude equivalent, usually about 6,000–8,000 feet. At that lower ambient pressure, the amount of oxygen available to your blood decreases, which can lead to hypoxemia if your body doesn’t get enough oxygen. Supplemental oxygen is used to prevent or treat that drop in arterial oxygen and keep tissues well oxygenated. That’s why the trigger for in-flight oxygen therapy is the presence of cabin altitude–induced hypoxemia.

Other scenarios don’t reliably indicate the need for oxygen. A minor headache can have many causes and isn’t a definitive sign of low blood oxygen, and oxygen therapy isn’t something you’d rely on only on the ground or to fix humidity-related issues.