PMID: 9184735Jun 1, 1997Paper

Ventilatory capacities at sea level and high altitude

Aviation, Space, and Environmental Medicine
V A ForteA Cymerman

Abstract

Because air is less dense at high altitude (HA), airway resistance is reduced and maximum inspiratory and expiratory flows are greater than at sea level (SL). Despite the reduction in airway resistance, ventilatory muscle endurance may be decreased by hypobaric hypoxia and, thus, may be a factor in limiting exercise at HA. To explore the effects of HA on ventilatory capacities and their relation to ventilatory demands of exercise, we measured 15-s maximum voluntary ventilation (MVV), 15-min maximum sustainable ventilation (MSV), and maximum airway pressures (Plmax and PEmax) in 18 healthy young men at SL and HA (Pikes Peak, 4300 m, or hypobaric chamber, PB approximately 460 mmHg). In eight of these subjects ventilatory capacities were compared with exercise ventilations. We also measured the effects of 36% O2 on the MSV in 12 of the subjects exposed to simulated altitude. Similar results were obtained at either simulated or actual HA. We found that MVV increased (p < 0.001) by 20% and the MSV (p < 0.001) by 15% at HA. Administration of 36% O2 at HA increased MSV further by 5% with no effect on MVV. No effect of HA on maximum inspiratory and expiratory pressures was found. We confirmed previous findings of modest increases in fo...Continue Reading

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