Journal of Applied Physiology, Vol 52, Issue 6 1393-1399, Copyright © 1982 by American Physiological Society
Man at extreme altitude
J. B. West
The history of man's attempts to learn more about the physiology of extreme
altitudes is briefly reviewed. The earliest exploits were by balloonists
who were often exposed to very severe hypoxia, sometimes with fatal
consequences. A turning point was the work by Paul Bert using low-pressure
chambers; he was able to prove that the deleterious effects of low
barometric pressures were caused by the low PO2, though other explanations
for mountain sickness such as a low aterial PCO2 continued to be promoted
for some time. Many early physiologists believed that active secretion of
oxygen by the lungs was necessary to explain man's tolerance of extreme
altitudes. Indeed, Haldane championed this view until his death in 1936,
though strong evidence to the contrary had accumulated since the work of
Krogh and others in the first decade of the century. High climbs by
mountaineers have stimulated much interest in the physiology of severe
hypoxia. Norton reached over 8,500 m on Mt. Everest in 1924, but the summit
was not attained without supplementary oxygen until 1978--the last 300 m
took 54 years! This suggests that the summit, altitude 8,848 m, is very
near the limit of human tolerance, and predictions based on maximal work
levels measured at lower altitudes are consistent with this. The American
Medical Research Expedition to Everest, 1981, was specifically planned to
obtain data on human physiology at extreme altitudes, and a number of
measurements were made over 8,000 m, including some on the summit itself.
It is apparent that the mountain can be climbed without supplementary
oxygen only because the barometric pressure at the summit is not as low as
has often been predicted, and because of the extreme hyperventilation that
man develops under these conditions.
