Altitude Sickness

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Medical Author:

Eric A Nazziola, MD

Coauthor:

John Lafleur, MD

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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• Altitude Sickness Overview
• Altitude Sickness Causes
• Altitude Sickness Symptoms
• When to Seek Medical Care
• Altitude Sickness Diagnosis
• Altitude Sickness Treatment
• Altitude Sickness Self-Care at Home
• Altitude Sickness Medical Treatment
• Altitude Sickness Follow-up
• Altitude Sickness Prevention
• Altitude Sickness Prognosis
• Altitude Sickness Pictures
• Authors and Editors
• Read more on Mountain Sickness from Healthwise

Altitude Sickness Overview

Altitude sickness (mountain sickness) is an illness that ranges from a mild headache and weariness to a life-threatening build-up of fluid in the lungs or brain at high altitudes.

Acute altitude sickness is the mildest and most common form. Because more people are traveling to areas of high elevation for skiing and mountain climbing, acute altitude sickness has become a greater public health concern. Roughly one fourth of Colorado ski area vacationers, two thirds of climbers on Mount Rainier, and half the people who fly to the Khumbu region of Nepal develop acute altitude sickness.

A more serious form of altitude sickness is high altitude pulmonary edema (HAPE). This illness occurs when fluid builds up within the lungs, a condition that can make breathing extremely difficult. Usually, this happens after the second night spent at a high altitude, but it can happen earlier or later. HAPE often comes on quickly. If left untreated, it can progress to respiratory collapse and ultimately to death. HAPE is the number one cause of death from altitude sickness.

Another severe form of altitude sickness is high altitude cerebral edema (HACE), in which fluid builds up within the brain. As the brain swells with fluid, the person's mental state changes. Loss of coordination, coma, and, finally, death can follow unless the problem is recognized and treated promptly.

Altitude Sickness Causes

Altitude sickness develops when the rate of ascent into higher altitudes outpaces the body's ability to adjust to those altitudes.

Altitude sickness generally develops at elevations higher than 8,000 feet (about 2,400 meters) above sea level and when the rate of ascent exceeds 1,000 feet (300 meters) per day.

The following actions can trigger altitude sickness:

• Ascending too rapidly
• Overexertion within 24 hours of ascent
• Inadequate fluid intake
• Hypothermia
• Consumption of alcohol or other sedatives

One way to avoid altitude sickness is allowing the body to get used to the altitude slowly.

• Acclimatization is the process by which the body adjusts to high altitudes.
• The goal of acclimatization is to increase ventilation (breathing) to compensate for lower oxygen content in the air.
• To compensate for this extra ventilation, blood needs to have a lower pH. In response, the kidneys excrete bicarbonate into the urine, which in turn lowers the body's pH to accommodate for this extra respiratory effort.