Altitude sickness

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Altitude sickness, also called mountain sickness, is an illness that occurs when the body is unable to adjust to high elevations. Symptoms of mountain sickness range from a mild headache and fatigue to a life-threatening build-up of fluid in the lungs or brain.
People may be exposed to high altitudes when they go rock climbing, mountain climbing, or skiing. At higher altitudes, there is less oxygen in the air. If a patient does not allow the body sufficient time to adjust to changes in altitude, the body does not receive enough oxygen, and symptoms of mountain sickness develop. Individuals who live at high elevations generally do not experience mountain sickness because their bodies are adjusted to the altitude.
Most patients will experience a full recovery if they start to descend to lower elevations shortly after symptoms of mountain sickness develop.
There are four forms of mountain sickness: acute mountain sickness, high altitude pulmonary edema, high altitude cerebral edema, and high altitude retinal hemorrhage.
Acute mountain sickness (AMS) is the mildest and most common type of mountain sickness. Mountain sickness typically develops when patients travel to elevations higher than 8,000 feet above sea level at a rate that is faster than 1,000 feet per day. Researchers estimate that nearly 50% of people who start at or near sea level and climb to 14,000 feet without scheduling rest time develop this condition.
If patients with AMS continue to climb or travel to higher elevations despite their symptoms, their condition may progress to a more severe form, such as high altitude pulmonary edema (HAPE). This condition occurs when fluid builds up in the lungs, making breathing difficult. Additional treatments, such as supplemental oxygen, may help reduce symptoms. If left untreated, the condition can lead to respiratory failure and death. HAPE is the number one cause of death from mountain sickness.
AMS may also develop into a severe condition called high altitude cerebral edema (HACE). This condition occurs when fluids builds up inside the brain, causing the brain to swell. As the brain swells, the person begins to feel confused and coordination becomes impaired. Some patients may experience permanent mental impairment and loss of coordination. The severity of these impairments varies among patients. If HACE is not treated, patients will develop a coma and die. More than 50% of HACE patients who develop a coma die.
Some patients with AMS may develop high altitude retinal hemorrhage (HARH). This condition occurs when there is bleeding in the eye(s). Bleeding may not be visible to the patient. A common symptom is blurred vision. Left untreated, HARH may lead to permanent eye damage or vision loss.
Patients with mountain sickness may develop HAPE, HACE, or HARH separately, or they may develop more than one of these conditions at the same time.

Related Terms

Acclimation, altitude, altitude sickness, AMS, cerebral edema, coma, CPAP, edema, Gamow bag, HACE, HAPE, HARH, high altitude sickness, hyperbaric chamber, hyperbaric therapy, mountain climbing, mountain sickness, ophthalmoscopy, oxygen, oxygen saturation, pulmonary edema, pulse oximetry, respiratory failure, retina, supplemental oxygen.