Altitude sickness overview

Overview
Every year, thousands of trekkers, skiers, climbers, security forces, rescuers, and others ascend to high altitudes with little or no time for acclimatization. The unacclimatized traveler ascending at such high rate are at risk for developing high altitude illness. Altitude sickness, also known as acute mountain sickness (AMS) or altitude illness is a pathological condition that is caused by acute exposure to low air pressure (usually outdoors on high altitudes). It commonly occurs above 2,400 metres (approximately 8,000 feet). Acute mountain sickness can progress to high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE). Altitude sickness does not typically affect persons traveling in aircraft, as the cabins of modern airplanes are pressurized. Another rarer type of altitude sickness caused by prolonged exposure to high altitude is chronic mountain sickness, also known as Monge's disease.

Generally, different people have different susceptibilities to altitude sickness. For some otherwise healthy people Acute mountain sickness (AMS) can begin to appear at around 2000 meters (6,500 feet) above sea level such as at many mountain ski resorts. AMS is the most frequent type of altitude sickness encountered. Symptoms often manifest themselves 6 to 10 hours after ascent and generally subside in 1 to 2 days, but they occasionally develop into the more serious conditions. Symptoms are described as headache with fatigue, stomach sickness, dizziness, and sleep disturbance as additional possible symptoms. Exertion aggravates the symptoms.

High altitude pulmonary edema (HAPE) and High altitude cerebral edema (HACE) are the most ominous of these symptoms, while acute mountain sickness, retinal haemorrhages, and peripheral edema are the less severe forms of the disease. The rate of ascent, the altitude attained, the amount of physical activity at high altitude, as well as individual susceptibility, are contributing factors to the incidence and severity of high-altitude illness.

Altitude sickness usually occurs following a rapid ascent and can usually be prevented by ascending slowly. In most of these cases, the symptoms are only temporary and usually abate with time as altitude acclimatisation occurs. However, in more extreme cases symptoms can be fatal.

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