Altitude Illness Among Tourists Flying to 3740 Meters
Elevation in the Nepal Himalayas
David R. Murdoch
Acute mountain sickness (AMS) is a syndrome that
occurs at altitudes over 2500 m. It is more common
among those who ascend rapidly.' Graded ascent is the
best prophylaxis for AMS. Current recommendations
are to avoid abrupt ascent to sleeping altitudes greater than
3000 m.Then each night spent above 3000 m should average not more than 300 m above the last, with a rest day
every 2 or 3 days (or every 1000 m).'.2
The Mount Everest region of Nepal is a popular high
altitude destination for tourists. Traditionally, visitors
have trekked into the area from low altitude over several days, either starting fiom an airstrip at 2800 m or fiom
walking in from 1860 ni over a longer period. A gradual ascent schedule assists acclimatization. Nevertheless,
between 43% and 57% of trekkers experience AMS."-"
Over recent years, a small airstrip at Shyangboche (3740 m)
has opened up to regular helicopter and fixed wing
flights, thereby allowing more rapid access into the
region.This airstrip was originally built to serve Hotel
Everestview, a hotel situated near Shyangboche, which
is at a 3860 m elevation that affords excellent views of
Mount Everest. Guests typically fly directly from Kathmandu (1300 m) to Shyangboche, walk the short distance
to the hotel, stay 1 or 2 nights, and then fly back to Kathmandu. Bottled oxygen is available at the hotel, but no
trained medical personnel are in residence. Regular commercial flights to Shyangboche, unrelated to Hotel EverestView, are now also in progress.These flights provide
the opportunity for large numbers of tourists to be
rapidly transported to high altitude without the benefit
of prior acclimatization. This new situation raises concerns about the risks of altitude illness.
David R. Murdoch, MB, ChB, DTM&H, MACTM, Department
of Microbiology, Canterbury Health Laboratories,
Christchurch Hospital, Christchurch, New Zealand.
Reprint requests: Dr. David Murdoch, Department of
Microbiology, Canterbury Health Laboratories, Private Bag
151, Christchurch, New Zealand
J Travel Med 1995; 2:255-256.
To assess the risk of developing A M S among those
who fly directly to 3740 m, a survey was carried out at
Hotel Everestview. Between December 1992 and May
1993, all guests staying at the hotel were given questionnaires to complete prior to departure. The questionnaires were available in Japanese and English; they
recorded basic demographic data, method of ingress,
and recent high altitude exposure.The presence ofAMS
was determined by the Lake Louise consensusAMS self
assessment scoring system.'A score of three or more was
regarded as diagnostic for AMS.
All 158 guests who stayed at Hotel Everestview during the study period completed the questionnaire. Four
were excluded because they were on descent, having
already spent several nights at altitudes higher than the
hotel.The remaining 154 were used for analysis.The mean
age of the subjects was 45.3 years (range 12 to 93 years)
and 84 (55%) were male.Japanese were the predominant
ethnic group, comprising 124 (81%) of the sample. O n e
hundred and sixteen (75%) had flown to the Shyangboche
airstrip (3740 m), whereas the remaining 38 had walked
up from altitudes under 3000 m over a few days. None
of the guests had been over 2500 m in the 4 weeks preceding this excursion. Ninety-two (60%) stayed 2 nights
at the hotel, the remainder staying only 1 night.
Ninety-seven (84%) of those who flew directly to
3740 m developed AMS.This compares with 22 (61%)
of those who walked up to the hotel (95% CI for difference = 6 to 4096, x 2 = 8.87, p < 0.01). Only 28 (24%)
of those who flew to Shyangboche reported that symptoms ofAMS did not affect their activities, whereas 18
(16%) reported a severe reduction in activities requiring
bedrest. Only one of the subjects who had walked up to
the hotel was bedridden, whereas 17 (45%) were unaffected. Bottled oxygen was administered to 45 (29%) subjects, only two ofwhom did not have AMS. Overall, 89%
of females experienced AMS, compared with 69% of
males (95% CI for difference = 7 to 32%, x 2 = 8.46, p
< 0.01). In this study, of those who flew to Shyangboche,
21 took acetazolamide, and all but one of these developedAMS.Although unclear, it appears that this drug was
administered by hotel staff as treatment rather than as a
prophylactic measure.
255
256
The most important single finding arising from this
study is that 84% of unacclimatized subjects developed
AMS after flying directly to 3740 m and sleeping at
3860 m. Few other studies examine altitude illness after
such rapid ascent to similar elevations. Eighty percent of
shiftworkers at the United Kingdom infrared telescope
on Mauna Kea (4200 m), Hawaii, were afTected by AMS.'
These workers usually slept at 3000 m, but they made
frequent journeys between sea level and the mountain
summit by motorized vehicle. Rapid ascent of Mount
Rainier (4392 m) from near sea level in under 48 hours
was associated with AMS in 67 to 77% of climbers.'~' A
higher incidence ofAMS in females compared to males
has been noted before,"' although most studies have
found both sexes to be equally affected.
Clearly, the presence of altitude illness had a major
effect on activities of those who flew directly to 3740 m.
One sixth were bedridden by their symptoms. Some of
those most severely affected may have developed high altitude cerebral or pulmonary edema, the life-threatening
forms of altitude illness, but this is impossible to determine without further information.The availability of supplementary oxygen, the lack of exertion and further
ascent, and the ability to fly guests back to Kathmandu
each morning (weather permitting) may have prevented
further deterioration and fatalities.
It cannot be overemphasized that the best way to prevent altitude illness is to ascend gradually. However, for
those willing to risk rapid ascent, the use of pharmacologic prophylaxis against AMS should be considered.
Acetazolamide is the agent most commonly used and is
more effective than dexamethasone." The usual prophylactic dose is 250 mg twice daily or 500 mg slow
release daily, commencing at least the night before ascent
to high altitude.
The traditional gradual ascent schedule followed by
most trekkers in the Mount Everest region of Nepal
reduces the impact of altitude illness.The ease with which
people can now fly directly to altitudes above 3500 m,
and the proportion who can expect to experience AMS
as demonstrated in this study, are causes for concern.
J o u r n a l o f Travel M e d i c i n e , V o l u m e 2, N u m b e r 4
Whenever possible, abrupt ascent to sleeping altitudes
above 3000 m should be avoided.
Acknowledgments
The author thanks the staff of Hotel Everestview
for their cooperation throughout the study.
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