Hypoxia is the condition that occurs when the body does not obtain substantial oxygen. Lack of oxygen is one of the most dangerous conditions at high altitudes, especially when coupled with inadequate pressure and/or temperatures. When a pilot inhales air at high altitudes, there is not enough pressure to force sufficient amounts of oxygen to the lungs, causing the function of various organs, including the brain, to be impaired.

Hypoxia is difficult to detect and, unfortunately, the nature of hypoxia makes the pilot the poorest judge of when it occurs. The first symptoms of oxygen deficiency resemble mild intoxication from alcohol. Most humans are completely unaware of this state of affairs and ‘believe’ they are fully conscious, when in actual fact they are in a comatose state.

The following suggestions can prevent hypoxia from getting a foot in your door:

1. Carry oxygen and use it before you start to become hypoxic. Measure your oxygen needs by the altimeter. Use oxygen on every flight above 12,500 feet.
2. If you do not count on a supplemental oxygen source, do not fly above 12,500 feet. If bad weather is in your course, avoid it by going around instead of climbing to higher altitudes.
3. Pilots who are older, overweight, or smoke heavily should limit themselves to a ceiling of 10,000 feet flying levels unless supplemental oxygen is available.
4. Use oxygen on long flights at or above 10,000 feet.
5. Use oxygen on night flights at or above 5,000 feet.
6. When using oxygen breathe normally. Extremely deep oxygen breathing can also cause loss of consciousness.

Besides the aforementioned recommendations, if you want to be a modern precautionary pilot you can carry a simple electronic instrument called pulse oximeter which clips on your fingertip, measures the oxygen saturation of the blood and instantly displays it on a tiny digital screen. It works as a “hypoxia tester” and could become your inseparable ally.