Wilderness: Altitude Sickness

• Altitude Sickness Overview
• Altitude Sickness Symptoms
• Altitude Sickness Treatment
• When to Seek Medical Care
• For More Information
• Web Links
• Synonyms and Keywords
• Authors and Editors

Altitude Sickness Overview

Acute mountain sickness (AMS), or altitude sickness, occurs in up to 67% of people who rapidly ascend above 8,000-10,000 feet (moderate altitude) over a period of 1-2 days. Symptoms (primarily headache) can appear within hours.

High-altitude pulmonary edema (HAPE) occurs when the air spaces of the lungs fill with fluid from leaking pulmonary blood vessels. This makes breathing and oxygenation difficult. While rare, high-altitude pulmonary edema is the most frequent cause of death in people with altitude illness. Symptomatic high-altitude pulmonary edema occurs in 2-4% of people who ascend to altitudes above 14,000 feet.

High-altitude cerebral edema (HACE) occurs when the brain swells due to fluid retention and low oxygen levels. This causes confusion and disorientation. High-altitude cerebral edema is the least common, but most severe, form of altitude illness. While less common than high-altitude pulmonary edema, high-altitude cerebral edema frequently occurs in people who already have high-altitude pulmonary edema.

Both high-altitude pulmonary edema and high-altitude cerebral edema are more common in people who ascend too rapidly and who continue to sleep at higher altitudes despite having symptoms of acute mountain sickness at lower elevations. Both conditions are gradually progressive and tend to occur over a period of days.

Women in the premenstrual water-retaining phase are more likely to develop symptoms.