[citation needed] Both rate of decompression and pressure difference affect the type of injury likely and the severity of the consequences.
[citation needed] There are three principal physiological effects arising from decompression at altitude: decompression sickness due to bubble formation in the tissues similar to those caused by decompression after exposure to pressures higher than sea level atmospheric pressure, barotrauma caused by the over-expansion of gas-filled spaces, and altitude sickness, a manifestation of hypoxia due to the naturally low partial pressure of oxygen in the air at altitude.
[9][10] Such decompression may be classed as explosive, rapid, or slow:[10] Altitude sickness, also known as acute mountain sickness (AMS), altitude illness, hypobaropathy, or soroche, is a pathological effect of high altitude on humans, caused by acute exposure to low partial pressure of oxygen and respiratory alkalosis arising from low partial pressure of blood carbon dioxide caused by hyperventilation.
Above the Armstrong limit, the atmospheric pressure is sufficiently low that exposed water boils at normal human body temperature.
Loss of consciousness is due to hypoxia and is followed by a series of changes to cardiovascular and neurological functions, and eventually death, unless pressure is restored in 60–90 seconds.
[2] On Earth, the Armstrong limit is around 18–19 km (11–12 mi; 59,000–62,000 ft) above sea level,[2][12] above which atmospheric air pressure drops below 0.0618 atm (6.3 kPa, 47 mmHg, or about 1 psi).