Journal of Applied Physiology, Vol 62, Issue 2 640-645, Copyright © 1987 by American Physiological Society
Breathing pattern in hypoxic exposures of varying duration
P. R. Bender, J. V. Weil, J. T. Reeves and L. G. Moore
The relative contributions of breathing frequency and tidal volume to the
increase in ventilation during acute or prolonged exposure to hypoxia is
uncertain. We examined the changes in breathing pattern during hypoxic
exposures lasting minutes, hours, and days using data from previous
studies. Increased tidal volume accounted for the increased ventilation
during 7-10 and 30 min of isocapnic and poikilocapnic (no CO2 added)
hypoxic exposures as well as during 7 h of poikilocapnic hypobaric hypoxia
(4,800 m). Tidal volume was also a greater overall contributor than
frequency to increased ventilation in sea-level residents during 3 days of
isocapnic hypobaric hypoxia (4,100-4,600 m) and in Denver (1,600 m)
residents during 5 days on Pikes Peak (4,300 m). In sea-level residents
during 3 days of poikilocapnic hypobaric hypoxia (3,600-4,300 m) and during
7-8 days on Pikes Peak, increased frequency accounted for the rise in
ventilation. Tidal volume thus contributed more than frequency to
increasing ventilation during brief hypoxia, whereas the contribution of
frequency was increased in prolonged hypoxia involving a 4,300-m altitude
ascent and hypocapnia.
