Nancy Adaptation tolife at the altitude of the summit of Everest
Zubieta-Castillo G., Zubieta-Calleja G.R., Zubieta-Calleja L., Zubieta-Calleja
High Altitude Pathology Institute (IPPA), La Paz, Bolivia
Centuries have shown us that as far as knowledge
and technologies improve, humans are able
to surmount challenges previously considered
impossible. Less than forty years ago, some scientists
believed that prolonged human occupation
of altitudes over 3000 meters was impossible.
(In fact, this remains a belief among those for
whom comfort is the main objective in life). How-ever,
such perspectives fail to consider the growing evidence
that humans (and animals) have an
extraordinary adaptive capacity to survive in the
most difficult environments presented on the planet.
From the 19th century it was claimed that
Mt. Everest was impossible to climb, through
Malloryґs inconclusive effort to the ultimate oxygen-assisted
success of Norgay and Hillary (and later Messner and Habelerґs oxygen-less ascent),
demonstrated hundreds of times that humans
have the physiological capacity to ascend the
highest point of the Farth. Careful preparation
of the expeditions, experience, persistence and
extraordinary stamina allowed Sir Edmund Hillary
and Tensing Norgay to stand on the top of
the mountain—and such is the approach of those
who have followed. But the remarkable conclusion
to be drawn from the history of such feats,
combined with our current knowledge of the potentialities
of human physiology, is that not only
humans can ascend to such altitudes, but that
they can dwell there, as well.
Human excursions to the highest realms of
the planet, under acute conditions without complete
adaptation and with imminent risk of death,
demonstrate that sufficient mechanisms of tissue
oxygenation are present to warrant such radical
conclusions as prolonged habitation at these
same extreme altitudes.
We have noted that in severe CMS and in
the example of the woman with CMS and triple
hypoxia syndrome, patients continue to arrive
ambulatory at IPPA for consultation with a
paO2 of around 35 mmHg. Such extreme hypoxic
states can be sustained over several weeks,
if not treated promptly. These low paO2 values
are comparable to those estimated for humans
at the summit of Mt. Everest . Increased
polycythemia is related not only to the severity
of respiratory insufficiency— other factors play
a role, as many researchers pointed out at the
4th World Congress on Mountain Medicine and
Physiology Arica, Chile 2000 .
If we acknowledge that individuals with advanced pathological lesions are able to adapt to
such hypoxic conditions as shown above, normal people should be able to do so even more
easily (with the qualification that there are different
individual and ethnic capacities). Further-more,
when a patient with CMS has a low paO2,
it is as if he or she were actually living at a higher altitude.
In order to better illustrate this, we
present an adapted graph plotting paO at different altitudes to depict at what relative altitude
CMS patients are living (Fig. 4).
Thus, the forgoing observations have led to
the formulation of our hypothesis that human
beings can adapt to the altitude and hypoxic conditions found at the summit of Mt. Everest. Such
adaptation, of course, is predicated upon adequate
protection from the cold, appropriate shelter and proper nutrition for such an environment.
Furthermore, our hypothesis stipulates gradual
exposure to increased hypoxia over extended
periods at intermediate altitudes, though within
an individual’s lifetime. We can summerize that,
prolonged human occupation is possible at such
extreme altitudes as Mt. Everest. If history is
any guide, it may be inevitable, as well.
Hematological adaptation to high altitude conserves energy expenditure of the pneumodynamic
and hemodynamic pumps which work harder at the beginning of acute exposure to hypoxia (such
as happens during exercise and after phlebotomy), in the interim of adaptation at the tissue level.
The first, then, is an acute phase and the other is a chronic phase.
Of course, we are not suggesting that colonies could be established on the summit of Mt
Everest. But we are convinced that the physiological attributes of humans allow for such possibility of adaptation to extreme hypoxia. Life is
possible anywhere on this planet, providing adequate nutrition and housing, and enough time is
allowed for gradual adaptation. This knowledge
permits us to understand the mechanisms of adaptation to tissue hypoxia in such a manner that
may someday be applicable and beneficial to
habitation of such adverse environments.
In this paper we have tried to explain the
foundations of our hypothesis that humans have
the capacity to adapt to life on the summit of Mt
Everest in one generation. If there is no first
generation in a new environment we cannot expect that other generations will follow. The latter
affirmation suggests that humans are already
genetically prepared for life in the highest point
of the planet—although not every single human
being. Some will be genetically incompatible or
incapable, as for example those suffering pulmonary fibrosis or Down’s syndrome or thousands
of other genetic variations in people living
at sea level which are not conducive to high altitude adaptation.
Acknowledgement: To Michael Moretti for the English correction of the manuscript and to the
Instituto Geografico Militar for their invaluable assistance
with the research in Chacaltaya
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