[High altitude sickness - review]

High altitude sickness is a common name for illnesses that can occur at high altitude, usually above 3000 meters from sea level. The cause is hypoxia but the pathophysiology of the diseases is a complex mixture of multiple factors, involving the human response to hypoxia. The most common symptom is headache, but loss of appetite, nausea and sleep disturbances are also common complaints. With rapid or high ascent there is increased risk of acute mountain sickness, with severe headache that responds poorly to pain medications, nausea, vomiting and extreme fatigue as the most common symptoms. The most severe forms of high-altitude sickness are high altitude cerebral edema and high altitude pulmonary edema. High altitude sickness can be prevented by slow ascent and avoiding overexertion. Medications can also be used to reduce symptoms. In this overview high altitude physiology and acclimatisation are reviewed. The main types of high altitude sickness are described with special emphasis on symptoms and diagnosis, but treatment and prevention are also reviewed.