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Stephen J.LurieMD, PhD, Contributing EditorIndividualAuthor
To the Editor: The use of supplemental oxygen
by Himalayan mountaineers has been debated for more than 8 decades.1 Although sometimes viewed as unsporting, supplemental-oxygen
use may improve survival rates by increasing performance and lowering hypoxic
Analyses of death rates of mountaineers descending from high summits may reveal
an impact of supplemental oxygen on survival because descending mountaineers
are often near exhaustion and vulnerable to accident, storm, or illness during
We analyzed interview data4-6
and more recent data (Elizabeth Hawley, oral communication, May 4, 2000) on
all mountaineers reaching the summit of the 2 highest peaks (Everest and K2)
from 1978 (year both summits first reached without supplemental oxygen) through
1999. For "summit-team" analyses on Everest, we excluded recent data (1993-1999)
to reduce the impact of guided expeditions, which may include inexperienced
climbers. We used exact logistic regression (conditional maximum likelihood)
with survival as the dependent variable and supplemental oxygen (used and
not used) as a factor, stratified by mountain (Everest and K2). In a preliminary
analysis, the year of summiting (covariate) was unrelated to individual death
rates on Everest (either directly or via an interaction with supplemental
oxygen, P>.27) and hence excluded from final analyses.
Individual mountaineers not using supplemental oxygen had significantly
higher death rates during descent than did those using supplemental oxygen
(Table 1, P<.001). This pattern is especially evident on K2, where approximately
1 in 5 climbers not using supplemental oxygen died during descent (Table 1).
To control for nonindependence of climbers in a team, we used a "summit
team" as a complementary unit of analysis and determined (for each team reaching
the summit on a given day and route) whether supplemental oxygen was used
and whether any descending mountaineer died. Number of summiters was a covariate
because the probability of a death(s) may increase with the number of climbers
exposed to risk. Even by this conservative analysis, teams not using supplemental
oxygen had relatively high death incidences (P=.03).
Reaching the summit of Everest, and especially of K2, is dangerous.
Overall, 1 in 29 climbers died during descent on Everest, and 1 in 7 died
on K2 (Table 1). Reaching those
summits without supplemental oxygen is associated with an even higher risk:
1 climber in 12 died on Everest, and approximately 1 in 5 died on K2 (Table 1). The survival impact of supplemental
oxygen may be greater than suggested because mountaineers not using supplemental
oxygen are probably relatively more experienced and therefore might be expected
to have lower death rates. The association may be causal because supplemental
oxygen decreases exposure time and reduces physical deterioration.1,3 Nevertheless, alternative explanations
(eg, mountaineers using supplemental oxygen are more risk averse) cannot be
excluded. Moreover, a full risk assessment of supplemental oxygen use awaits
incorporation of data on death rates during ascent, risk to porters ferrying
oxygen canisters, actual causes of death, and weather conditions. In any case,
Himalayan mountaineering is a dangerous activity2
that balances adventure against risk. Mountaineers considering whether to
use supplemental oxygen should consider the risk of death during descent.
Funding/Support: This study was funded by a
fellowship to Dr Huey from the J. S. Guggenheim Fellowship.
Acknowledgment: We thank T. Hornbein, MD, University
of Washington, Seattle, and C. Houston, MD, University of Vermont, Burlington,
for advice, and E. Hawley, Consul for New Zealand, Kathmandu,
Nepal, for sharing data.
Fontanarosa PB, Huey RB, Eguskitza X. Supplemental Oxygen and Mountaineer Death Rates on Everest and K2. JAMA. 2000;284(2):181. doi:10.1001/jama.284.2.175
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