Acute mountain sickness Health Article

Definition

Acute mountain sickness is an illness that can affect mountain climbers, hikers, skiers, or travelers at high altitude (typically above 8,000 feet or 2,400 meters).

Alternative Names

High altitude cerebral edema; Altitude anoxia; Altitude sickness; Mountain sickness; High altitude pulmonary edema

Causes, incidence, and risk factors

Acute mountain sickness is brought on by the combination of reduced air pressure and lower oxygen concentration that occur at high altitudes. Symptoms can range from mild to life-threatening, and can affect the nervous system, lungs, muscles, and heart.

In most cases the symptoms are mild. In severe cases fluid collects in the lungs (pulmonary edema) causing extreme shortness of breath. This further reduces how much oxygen enters the bloodstream and reaches vital organs and tissue. Brain swelling may also occur (cerebral edema). This can cause confusion, coma, and, if untreated, death.

The chance of getting acute mountain sickness increases the faster a person climbs to a high altitude. How severe the symptoms are also depends on this factor, as well as how hard the person pushes (exerts) himself or herself. People who normally live at or near sea level are more prone to acute mountain sickness.

Approximately 20% of people will develop mild symptoms at altitudes between 6,300 to 9,700 feet, but pulmonary and cerebral edema are extremely rare at these heights. However, above 14,000 feet, a majority of people will experience at least mild symptoms. Some people who stay at this height can develop pulmonary or cerebral edema.

Symptoms

Symptoms generally associated with mild to moderate altitude illness include:

• Difficulty sleeping
• Dizziness or light-headedness
• Fatigue
• Headache
• Loss of appetite
• Nausea or vomiting
• Rapid pulse (heart rate)
• Shortness of breath with exertion

Symptoms generally associated with more severe altitude illness include:

• Bluish discoloration of the skin (cyanosis)
• Chest tightness or congestion
• Confusion
• Cough
• Coughing up blood
• Decreased consciousness or withdrawal from social interaction
• Gray or pale complexion
• Inability to walk in a straight line, or to walk at all
• Shortness of breath at rest

Signs and tests

Listening to the chest with a stethoscope (auscultation) reveals sounds called crackles (rales) in the lung, which can mean pulmonary edema.

A chest x-ray may be performed.