Respiration of man during exercise at high altitude: Highlander vs lowlander

Abstract

The regulation of pulmonary ventilation during exercise (O 2 uptake up to 1.4 L.min −1) was investigated in five high altitude natives (HN) and five sea level natives (SN) acclimatized to 4540 m (P b 445 torr). At ambient P io 2 (83 torr), HN ventilated 10–20% less than SN. Hypercapnic and non-chemical work stimuli produced similar additive ventilatory effects in HN and SN. The oxie slopes of e—P aco 2, response line, which were independent of work level, were also similar in the two groups. During hypoxic exercise, the slopes of the e—P aco 2 response increased, the increment being greater at higher work rates. This interaction between hypoxia and non-chemical work stimuli in HN was, however, a third or less of that in SN. Thus, we conclude that in the regulation of ventilation in HN and SN during exercise, the hypercapnic and non-chemical work stimuli played similar roles but that the relatively insensitive peripheral chemoreflex in HN resulted in a diminished interaction between the hypoxic and work stimuli.