Journal of Applied Physiology, Vol 73, Issue 5 1749-1755, Copyright © 1992 by American Physiological Society
Effects of a 1-yr stay at altitude on ventilation, metabolism, and work capacity
T. V. Serebrovskaya and A. A. Ivashkevich
A.A. Bogomoletz Institute of Physiology, Kiev, Ukraine.
The hypoxic and hypercapnic ventilatory drive, gas exchange, blood lactate
and pyruvate concentrations, acid-base balance, and physical working
capacity were determined in three groups of healthy males: 17 residents
examined at sea level (group I), 24 sea-level natives residing at 1,680-m
altitude for 1 yr and examined there (group II), and 17 sea-level natives
residing at 3,650-m altitude for 1 yr and examined there (group III). The
piecewise linear approximation technique was used to study the ventilatory
response curves, which allowed a separate analysis of slopes during the
first phase of slow increase in ventilation and the second phase of sharp
increase. The hypoxic ventilatory response for both isocapnic and
poikilocapnic conditions was greater in group II and even greater in group
III. The first signs of consciousness distortion in sea-level residents
appeared at an end-tidal O2 pressure level (4.09 +/- 0.56 kPa) higher than
that of temporary residents of middle (3.05 +/- 0.12) and high altitude
(2.90 +/- 0.07). The hypercapnic response was also increased, although to a
lesser degree. Subjects with the highest hypoxic respiratory sensitivity at
high altitude demonstrated greater O2 consumption at rest, greater
ventilatory response to exercise, higher physical capacity, and a less
pronounced anaerobic glycolytic flux but a lower tolerance to extreme
hypoxia. That is, end-tidal O2 pressure that caused a distortion of the
consciousness was higher in these subjects than in those with lower hypoxic
sensitivity. Two extreme types of adaptation strategy can be distinguished:
active, with marked reactions of "struggle for oxygen," and passive, with
reduced O2 metabolism, as well as several intermediate types.(ABSTRACT
TRUNCATED AT 250 WORDS)
