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Altitude sickness is typically mild but can sometimes turn very serious − a high-altitude medicine physician explains how to safely prepare

Brian Strickland, University of Colorado Anschutz Medical Campus, The Conversation on

Published in News & Features

Equipped with the latest gear and a thirst for adventure, mountaineers embrace the perils that come with conquering the world’s highest peaks. Yet, even those who tread more cautiously at high altitude are not immune from the health hazards waiting in the thin air above.

Altitude sickness, which most commonly refers to acute mountain sickness, presents a significant challenge to those traveling to and adventuring in high-altitude destinations. Its symptoms can range from mildly annoying to incapacitating and, in some cases, may progress to more life-threatening illnesses.

While interest in high-altitude tourism is rapidly growing, general awareness and understanding about the hazards of visiting these locations remains low. The more travelers know, the better they can prepare for and enjoy their journey.

As an emergency physician specializing in high-altitude illnesses, I work to improve health care in remote and mountainous locations around the world. I’m invested in finding ways to allow people from all backgrounds to experience the magic of the mountains in an enjoyable and meaningful way.

Altitude sickness is rare in locations lower than 8,200 feet (2,500 meters); however, it becomes very common when ascending above this elevation. In fact, it affects about 25% of visitors to the mountains of Colorado, where I conduct most of my research.

The risk rapidly increases with higher ascents. Above 9,800 feet (3,000 meters), up to 75% of travelers may develop symptoms. Symptoms of altitude sickness are usually mild and consist of headache, dizziness, nausea, fatigue and insomnia. They usually resolve after one to two days, as long as travelers stop their ascent, and the symptoms quickly resolve with descent.


When travelers do not properly acclimatize, they can be susceptible to life-threatening altitude illnesses, such as high-altitude pulmonary edema or high-altitude cerebral edema. These conditions are characterized by fluid accumulation within the tissues of the lungs and brain, respectively, and are the most severe forms of altitude sickness.

Altitude sickness symptoms are thought to be caused by increased pressure surrounding the brain, which results from the failure of the body to acclimatize to higher elevations.

As people enter into an environment with lower air pressure and, therefore, lower oxygen content, their breathing rate increases in order to compensate. This causes an increase in the amount of oxygen in the blood as well as decreased CO₂ levels, which then increases blood pH. As a result, the kidneys compensate by removing a chemical called bicarbonate from the blood into the urine. This process makes people urinate more and helps correct the acid and alkaline content of the blood to a more normal level.

High-altitude medicine experts and other physicians have known for decades that taking time to slowly ascend is the best way to prevent the development of altitude sickness.


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