Acute altitude sickness (AAS) is a collection of symptoms that occur in individuals moving from areas of lower elevation to higher elevation. Typically, AAS occurs in sea-level dwelling individuals who participate in mountain sports. Skiers, high altitude hikers, and mountaineers may all suffer from AAS upon initial ascent to higher elevations. Recognizing the signs and symptoms of AAS is vital to initiating treatment promptly, and preventing permanent damage or death.
Physiology of Acute Altitude Sickness
There is less available oxygen in the air at high altitude, compared with air at sea level. As the oxygen concentration in air decreases, the body struggles to get adequate oxygen to support body function. The body responds to the lowered oxygen content in the air with increased respiratory rate, deeper breathing, and higher “stroke volume” of the heart (more blood pumped per heartbeat). Additionally, arteries throughout the body dilate, in an attempt to supply more blood (and more oxygen) to the tissues. This hyperfunctioning state leaves the body vulnerable to AAS, particularly if the individual exerts him or herself.
Symptoms of Acute Altitude Sickness
- Loss of appetite.
- Severe headache, worsening with exertion.
- Nausea and vomiting.
- Shortness of breath and pulmonary edema (fluid in lungs).
- Fatigue.
- Insomnia.
- Onset of symptoms is usually 6-12 hours after arrival at high altitude.
Prevention of Acute Altitude Sickness
With ski season fast approaching, following these suggestions can help prevent losing time on the mountain to AAS:
- Stay lean and fit – According to a 2003 study in the journal Annals of Internal Medicine, obese individuals suffer from AAS at higher rates than the non-obese. Similarly, a study from 1993 showed that fit individuals were less likely to suffer from AAS than sedentary individuals.
- Ascend slowly – The more rapid the ascent to higher altitude, the greater the risk of AAS. Spending a night at an intermediate elevation prior to traveling to the final altitude will decrease the risk for AAS.
- Drink fluids – This is particularly important since the body loses more water at higher altitudes than at sea level. The resulting dehydration can worsen AAS.
- Rest on arrival – Consider the first day or two at high altitude as “rest days” if possible. Exercising at high altitude can exacerbate AAS.
- Increase carbohydrate consumption – Studies show that carbohydrates, which in general are the body's main fuel source, play an even greater role in maintaining normal function at higher altitude.
- Avoid alcohol consumption – Alcohol has a dehydrating/diuretic effect on the body, and can decrease respiration, worsening AAS.
Treatment for Acute Altitude Sickness
Use a common sense approach when feeling ill. Be aware of the symptoms, which can be mistaken for “food poisoning” or a bad cold. If symptoms occur soon after arrival to high altitude, rest and hydration are important first steps. If symptoms persist, travel to lower elevation may be necessary. If unsure, it is always best to seek medical attention promptly.
For more information, please see the Center for Disease Control website.
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