Background

Hypoxia is a state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs. Because of the nature of flight, flight crews are much more likely to suffer from hypoxia than “normal” people. Knowing what to look for and how to react to resolve the situation is essential to maintain flight safety. This Briefing Note defines hypoxia and describes the symptoms and performance decrements that can result from it. It is important for flight crews to understand the warning signs of hypoxia and how the human body responds to reduced levels of oxygen. Also included are some techniques that can help a flight crew member defend against the effects of hypoxia.

Introduction

Hypoxia from exposure to altitude is due entirely to the reduced barometric pressures encountered at higher altitudes. The concentration of oxygen in the atmosphere does not change as altitude increases; rather it stays constant at about 21%. Because of the decrease in barometric pressure, however, there is less atmosphere (air) at higher altitudes, which results in less available oxygen.