Lack of oxygen (hypoxia)

At every altitude the air is about 21 % oxygen. What changes is the air pressure: at 18,000 ft it is only about half of that at sea level.

With the air pressure, the oxygen pressure falls too: the pressure that moves oxygen from your lungs into your blood. When your blood takes up too little oxygen, that is hypoxia.

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040 · Human Performance

Lack of oxygen (hypoxia)

At every altitude the air is about 21 % oxygen. What changes is the air pressure: at 18,000 ft it is only about half of that at sea level.

With the air pressure, the oxygen pressure falls too: the pressure that moves oxygen from your lungs into your blood. When your blood takes up too little oxygen, that is hypoxia.