Travel Reference
In-Depth Information
al and other illnesses so common in developing countries do not lead to dehydration and
wasting. Such illnesses commonly have a greater impact on an expedition than weather or
terrain.
Acclimatization is thought to be lost at about the same rate it is gained. Once acclimat-
ized,notdescendingformorethanaweekortendaysappearsprudent.Furthermore,afully
acclimatized individualwhogoesdowntoalowaltitudeforlongerthanaweekortendays
is at increased risk of developing high-altitude pulmonary edema upon returning (“High-
Altitude Pulmonary Edema,” this chapter).
Inrecent years manypersonsplanning atriptomoderate altitude havetried toacclimat-
ize by spending an hour once or twice a day in a low-oxygen room or breathing a low-oxy-
gen gas mixture. A number of sports clubs and hotels in several countries offer such facil-
ities, and the process has been studied in a few research laboratories. Repeated short ex-
posures are not effective in stimulating acclimatization, although some regimens involving
longer exposure time may have some beneficial effects.
Someclimberswhohavemademanytripstohighmountainsbelievethebodyacclimat-
izes more rapidly and completely on later climbs. Some evidence supports the theory that
stays at high altitude within recent months speed acclimatization on subsequent ascents.
Others feel that increased familiarity with living and climbing at high altitudes is respons-
ible for the apparent greater acclimatization.
Apartfromacetazolamide,noartificialaidstoacclimatizationareknown.Susceptibility
to mountain sicknesses decreases with increasing age (one of the few benefits of aging),
but the ability to acclimatize also seems to decline slightly as people get older. Increased
physical fitness at sea level, however, increases exercise capacity at altitude and can make
a trip less physically stressful and more enjoyable.
Climberswhohavereachedthesummitofveryhighmountains—8000meters—without
supplemental oxygen have some inherent physiologic advantages that cannot be entirely
predicted by sea level studies. They are able to sustain very heavy exercise much longer
thanothers,andtheirmaximumexercisecapacityishigherthanmostathletes,althoughnot
as high as Olympic endurance athletes such as cross-country skiers. They are experienced
mountaineers with highly developed skills that enable them to climb efficiently and fast
withminimalenergyexpenditure.Enduranceathleteshavelungswithahigher-than-normal
diffusingcapacity,andtheyusuallyhaveanormalorincreasedventilatoryresponsetohyp-
oxia. Experience has given them confidence, reducing the anxiety felt by novices, which
also gives them an increased tolerance for hypoxia. Even when made acutely hypoxic at
sea level, they seem to fare better. However, some who have gone the highest without ill-
ness actually have a lower-than-normal hypoxic ventilatory response and must take longer
to acclimatize.
Summit of Mount Everest
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