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Altitude sickness, the mildest form being acute mountain sickness (AMS), is a harmful effect of high altitude, caused by rapid exposure to low amounts of oxygen at high elevation. [ 1 ] [ 2 ] [ 3 ] People's bodies can respond to high altitude in different ways.
Very high altitude = 3,500–5,500 metres (11,500–18,000 ft) Extreme altitude = above 5,500 metres (18,000 ft) Travel to each of these altitude regions can lead to medical problems, from the mild symptoms of acute mountain sickness to the potentially fatal high-altitude pulmonary edema and high-altitude cerebral edema .
Failure to acclimatize may result in altitude sickness, including high-altitude pulmonary edema or cerebral edema . [11] [12] Humans have survived for 2 years at 5,950 m (19,520 ft) [475 millibars (14.0 inHg; 6.89 psi) of atmospheric pressure], which appears to be near the limit of the permanently tolerable highest altitude. [13]
The sickness is compounded by related symptoms such as cerebral oedema (swelling of brain) and pulmonary oedema (fluid accumulation in lungs) . [ 17 ] [ 18 ] Over a span of multiple days, individuals experiencing the effects of high-altitude hypoxia demonstrate raised respiratory activity and elevated metabolic conditions which persist during ...
A pressure of 6.3 kPa—the Armstrong limit—is about 1/16 of the standard sea-level atmospheric pressure of 101.3 kilopascals (760 mmHg). At higher altitudes water vapour from ebullism will add to the decompression bubbles of nitrogen gas and cause the body tissues to swell up, though the tissues and the skin are strong enough not to burst ...
High-altitude cerebral edema (HACE) is a medical condition in which the brain swells with fluid because of the physiological effects of traveling to a high altitude. It generally appears in patients who have acute mountain sickness and involves disorientation, lethargy, and nausea among other symptoms.
First aid at altitude is oxygen at the highest practicable concentration and earliest and largest practicable reduction in cabin altitude. Ground-level 100% oxygen therapy is suggested for 2 hours following type-1 decompression sickness that occurs at altitude, if it resolves upon descent.
High-altitude climbing usually requires the use of portable oxygen apparatus when climbing Mount Everest or the other eight-thousanders, though some mountaineers—and alpine style climbers in particular—have deliberately ascended Everest without oxygen (e.g. starting with Reinhold Messner in 1978).