With the recent development of improved airports located closer to major ski resorts, the recreational skier no longer undergoes a gradual ascent to high altitude. You can actually be skiing at over 10,000 feet above sea level within hours of leaving home. Although convenient, this advance in travel has made altitude-related illness the most common medical ailment seen at ski-area clinics.

Most of the ski resorts in the Rocky Mountains are located at more than 8000 feet above sea level. At this altitude, your body must adapt to compensate for environmental differences, such as less oxygen in the air. To get enough oxygen into your blood and to your body tissues, you begin to breathe faster and deeper, which can lead to hyperventilation. Your heart rate and cardiac output (the amount of blood ejected with each heart beat) also increase. These adaptations help you increase the amount of oxygen that is taken in and delivered to the body tissues but, in so doing, seem to cause a fluid shift from inside the blood vessels to the surrounding tissues.

When the fluid increases in the tissues of the brain, it causes headaches and lightheadedness as well as nausea and sleep disturbance. Hyperventilation may contribute to these symptoms. Collectively, these symptoms are called acute mountain sickness (AMS). This condition is divided by severity into four classes ranging from mild symptoms that do not interfere with activity (class 1) to severe symptoms that often include swelling of the lungs or brain and necessitate immediate descent from the elevated area (class 4).

Most cases of AMS can be adequately treated with rest, fluids, and aspirin or acetaminophen (Tylenol). In some cases, treatment with oxygen is helpful but may postpone the adjustment process that ultimately must occur. The most effective treatment is prevention, and the ideal preventative measure is gradual ascent. As previously mentioned, gradual ascent is seldom accomplished in 1996, so the following measures should be followed: drink plenty of fluids before and during your stay, especially while you are skiing; avoid salty foods and alcohol; and ease into activity at high altitude rather than skiing hard the first day. Your doctor may prescribe the medication acetazolamide, which has been found to be highly effective at preventing AMS.

In addition to AMS, pre-existing conditions, such as coronary artery (heart) disease and pulmonary (lung) disease may be intensified by sudden changes in altitude. Any condition that makes it more difficult for the heart muscle or any other vital organ to receive oxygen will be worsened by the decrease in oxygen accompanying ascent to high altitude. Anyone with heart or lung disease should discuss plans for a ski vacation with their doctor.

Skiing is an exhilarating sport enjoyed by enthusiasts of all ages in environments that are breathtaking - literally. Activity at such high elevations has inherent risks that must be taken seriously in order for skiing to be enjoyed to its fullest. Remember that when you head for your next ski vacation and your well-meaning friends say, "Don't break a leg," an equally helpful warning would be, "Don't let the high get you down."

Jay W. McMurren, M.D.