Altitude Preexposure Recommendations for Inducing Acclimatization

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Altitude Preexposure Recommendations for Inducing Acclimatization

S.R. Muza, B.A. Beidleman, C.S. Fulco


For many low-altitude (<1500>2400 m) altitudes without having the time to develop an adequate degree of altitude acclimatization. Prior to departing on these trips, low-altitude residents can induce
some degree of altitude acclimatization by ascending to moderate (>1500 m) or high altitudes during either continuous or intermittent altitude preexposures. Generally, the degree of altitude acclimatization developed is proportional to the altitude attained and the duration of exposure. The available evidence suggests that continuous residence at 2200m or higher for 1 to 2 days or daily 1.5- to 4-h exposures to >4000m induce ventilatory acclimatization. Six days at 2200m substantially decreases acute mountain sickness (AMS) and improves work performance after rapid ascent to 4300 m. There is evidence that 5 or more days above 3000m within the last 2
months will significantly decrease AMS during a subsequent rapid ascent to 4500 m. Exercise training during the altitude preexposures may augment improvement in physical performance. The persistence of altitude acclimatization after return to low altitude appears to be proportional to the degree of acclimatization developed. The subsequent ascent to high altitude should be scheduled as soon as possible after the last altitude preexposure.
Key Words: altitude acclimatization; acute mountain sickness; high altitude
Introduction
Lowland (<1500 m) residents rapidly ascending to
high (>2400 m) and especially very high (>3500 m) or
extreme (>5500 m) altitudes are at risk of developing high
altitude illness (Gallagher and Hackett, 2004) and experiencing
substantial impairment of their physical and cognitive
work performance (Fulco et al., 1998). Altitude acclimatization
is a series of physiological adjustments that compensates
for the reduction in ambient oxygen. Altitude acclimatization
is the best strategy for the prevention of acute mountain sickness
(AMS) (Forgey, 2006) and allows people to achieve the
maximum physical and cognitive work performancs possible
for the altitude to which they are acclimatized (Fulco et al.,
2000; Banderet et al., 2002). A gradual or staged ascent with a
first-night sleeping altitude of no more than 2400m and daily
altitude gain limited to 300 to 600m is the recommended
strategy for induction of altitude acclimatization (Forgey, 2006).
However, for many climbers and trekkers on a tight schedule,
there may be insufficient time to develop an adequate degree of
U.S. Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Natick, Massachusetts, USA.
HIGH ALTITUDE MEDICINE & BIOLOGY
Volume 11, Number 2, 2010
ª Mary Ann Liebert, Inc.
DOI: 10.1089/ham.2010.1006
87