Altitude Sickness (Acute Mountain Sickness)

Ever exercised in the mountains? You probably noticed that oxygen can be a little thin up there. At 10,000 feet, for example, the air has only about 70 percent as much oxygen as it does at sea level. Whether you're hiking, lugging a pair of skis straight up a mountain, or simply standing around and taking in the sights, you'll have to breathe a little harder to get the oxygen that your body needs.

If your body isn't getting enough oxygen in the rarified air, you might start to notice signs of altitude sickness, also called acute mountain sickness or just mountain sickness. This condition is common at altitudes of about 8,000 feet and above, especially in people who aren't used to high altitudes. While the air is relatively thin in places like Denver, you generally need to be well over a mile above sea level to develop altitude sickness. If you think you have altitude sickness, don't go any higher until you feel better. And if you feel yourself getting worse, you need to find lower ground as soon as possible. If you don't act, a minor problem could turn into a medical emergency.

What are the symptoms of altitude sickness?

The symptoms of altitude sickness feel a lot like a hangover. Your head will start aching within 2 to 12 hours of reaching high altitude. You may also feel tired and nauseous, and you may start vomiting.

If a person becomes breathless even while resting, feels weak, and has a mild cough, he might have high-altitude pulmonary edema (HAPE), or swelling in the lungs. This condition can be fatal if he doesn't get oxygen or move at least 1,000 feet lower in elevation right away.

Extreme fatigue, confusion, and drowsiness are a sign of another potentially fatal complication, high-altitude cerebral edema or (HACE). A person with HACE needs to get to lower ground as soon as possible.

How can altitude sickness be prevented?

The best way to avoid altitude sickness is to acclimate yourself to thin air. If you're flying to a city that's at a high altitude, such as La Paz, Bolivia (12,000 feet), take it easy for a couple of days before you do any climbing. When climbing in high mountains, don't ascend more than 1,000 feet in a day. It's also a good idea to avoid alcohol for 48 hours before reaching high elevation. If you're concerned that you won't have time to fully acclimate yourself, ask your doctor about the possibility of taking acetazolamide (Diamox), a glaucoma drug that can help prevent altitude sickness.

How is altitude sickness treated?

If you get a headache from altitude sickness, take a couple of aspirin, acetaminophen, or another over-the-counter pain reliever. Altitude sickness can also be treated with medications such as Diamox and dexamethasone, a steroid drug. But the best treatment for altitude sickness is more oxygen. Moving to lower ground -- especially when faced with an emergency -- can be the best move you ever make.

References

Centers for Disease Control and Prevention. Altitude illness. 2009. http://wwwnc.cdc.gov/travel/yellowbook/2010/chapter-2/altitude-illness.aspx

American Heart Association. High-altitude sickness. 2010. http://www.americanheart.org/presenter.jhtml?identifier=4618

Altitude.org. Altitude sickness. 2010. http://www.altitude.org/altitude_sickness.php

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