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Chapter 10
HIGH-ALTITUDE ILLNESS
Recommendations are considered Category 1B, except where indicated 1A,2 or 3, by the
WMS Panel of Expert Reviewers.
I. GENERAL INFORMATION
In unacclimatized persons ascending to high altitude failure of the body to adapt to the
stress of hypobaric hypoxia may lead to the cerebral and pulmonary syndromes of high
altitude illness. Acute mountain sickness (AMS) and high altitude cerebral edema
(HACE) refer to the cerebral disorders, and high altitude pulmonary edema (HAPE) to
the pulmonary abnormalities. High-altitude illnesses affect large numbers of wilderness
travelers and result in occasional deaths. Proper management requires early diagnosis and
prompt intervention. Most importantly, preventative measures such as gradual ascent will
allow time for acclimatization and prevent high altitude illness.
II. GUIDELINES FOR PREVENTION
Most altitude illness is preventable. The following measures reduce the incidence and
severity of high-altitude illness. Although these measures do not guarantee freedom from
illness, they are highly recommended, especially for those without altitude experience.
A.
Staged Ascent: The best strategy for prevention of acute mountain sickness is a
gradual ascent to allow time for acclimatization (category 1A recommendation).
If possible, the first camp should be no higher than 8,000 feet (2,400 meters), with
an increase of no more than 1,000 to 2,000 feet (300 to 600 meters) per night. An
alternative approach is to spend two nights at the same altitude for every 2,000-
foot (600 meter) gain in altitude above 10,000 feet (3,000 meters). If a trip is
started at over 9,000 feet (2,700 meters), two nights may be spent acclimatizing at
that altitude before proceeding higher. Proceed higher during the day and return to
a lower elevation to sleep (climb high, sleep low).
B.
High-Carbohydrate Diet: A significant energy deficit may occur after ascent to
high altitude because appetite is suppressed, food may be less available or less
palatable, and energy expenditure is increased. Nutritional intake should be
increased by about 500 kcal per day above appetite emphasizing carbohydrate
rich foods, which may aid acclimatization and prevent altitude illness (category 2
recommendation).
C.
Appropriate Exercise Level: Until acclimatized, exercise moderately, avoiding
excessive dyspnea and fatigue.
D.
Hydration: To offset increased fluid losses at high altitudes, stay well hydrated.
Adequate hydration may be judged by the presence of clear urine. In the setting of
