Basic medical advice for travelers to high altitudes.

BACKGROUND: High-altitude travel, for mountain climbing, trekking, or sightseeing, has become very popular. Therefore, the awareness of its dangers has increased, and many prospective travelers seek medical advice before setting forth on their trip.

METHODS: We selectively searched the literature for relevant original articles and reviews about acclimatization to high altitude and about high-altitude-related illnesses, including acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) (search in Medline for articles published from 1960-2010).

RESULTS: High-altitude-related illnesses are caused by hypoxia and the resulting hypoxemia in otherwise healthy persons who travel too high too fast, with too little time to become acclimatized. The individual susceptibility to high-altitude-related illness is a further risk factor that can only be recognized in persons who have traveled to high altitudes in the past. In an unselected group of mountain climbers, 50% had AMS at 4500 meters, while 0.5-1% had HACE and 6% had HAPE at the same altitude. Persons with preexisting illnesses, particularly of the heart and lungs, can develop symptoms of their underlying disease at high altitudes because of hypoxia. Thus, medical advice is based on an assessment of the risk of illness in relation to the intended altitude profile of the trip, in consideration of the prospective traveler's suitability for high altitudes (cardiopulmonary performance status, exercise capacity) and individual susceptibility to high-altitude-related illnesses, as judged from previous exposures. The symptoms and treatment of high-altitude-related illnesses should be thoroughly explained.

CONCLUSION: An understanding of the physiology of adaptation to high altitudes and of the pathophysiology and clinical manifestations of high-altitude-related illnesses provides a basis for the proper counseling of prospective travelers, through which life-threatening conditions can be prevented.