What is altitude sickness?

Causes and Symptoms

There are four types of altitude sickness: acute mountain sickness, high-altitude pulmonary
edema (HAPE), high-altitude cerebral edema (HACE), and high-altitude retinopathy (HAR). Though most patients have mild symptoms, death is not uncommon in severe cases. Illness is associated with rapid ascent to mountain areas by tourists, skiers, and mountaineers. Residents of mountainous regions are less susceptible because their bodies have adapted to lower oxygen levels. It is estimated that up to one-quarter of tourists skiing in the mountains of the western United States have experienced some manifestations, although mild ones, of altitude sickness.

Acute mountain sickness is characterized by headache, decreased appetite, insomnia, fatigue, nausea, and onset at altitudes above 1,980 meters (6,500 feet). The risk of becoming affected increases with young age, quick ascent, and a past history of acute mountain sickness. Symptoms usually last for a few days. Between 5 and 10 percent of patients with acute mountain sickness progress to HAPE, which occurs when the small pulmonary blood vessels leak, allowing fluid accumulation in the lungs. Mortality from HAPE ranges from 11 to 44 percent. The related condition HACE occurs when fluid accumulation in the brain causes increased pressure within the skull. Neurologic signs such as confusion and coma may be noted.

Treatment and Therapy

Prevention is crucial to the reduction of morbidity and mortality from altitude sickness. Ascents should be slow, especially those involving physical exertion. Sedatives and salt should be avoided; alcohol should be avoided for the first forty-eight hours. Most people adapt to altitude changes within three days. Returning to lower altitudes at night is advised. Premedication with acetazolamide, a prescription drug, will hasten adaptation and reduce symptoms. In serious cases, descent to lower altitudes is vital. Corticosteroids, oxygen, and hyperbaric treatments may be used. Chronically ill persons should check with their doctors before attempting strenuous activity at high altitudes.

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