Respiration and heart rate of Sherpa highlanders during exercise.

Abstract

Oxygen uptake, ventilatory indices, and heart rate were measured in 9 human subjects during exercise performed at an altitude of 4,880 m. Responses of 4 Sherpa high altitude dwellers and of 5 lowlanders were compared at a research station in the Himalaya mountains over a period of 8 weeks. Oxygen uptake at a given work rate was similar in both groups and was independent of altitude. Ventilation was smaller and arterial PCO2 higher, at the steady state, among the Sherpas. The sensitivity of ventilation during exercise to alterations of PO2 of the inspired air, over a range of 79-150 mm Hg, was less in the Sherpas than in the lowlanders. Heart rate increased with exercise to a greater degree among the Sherpas, as did VO2- Inhalation of oxygen-rich gas mixtures decreased the slope of the heart rate-VO2 curve in these subjects, while in the lowlanders, this slope was increased on oxygen inhalation. Oxygen capacity of the blood and arterial oxygen saturation were similar in both groups, although blood pH was found to be lower in the Sherpas. The major conclusion drawn from these observations, that long-term and short-term altitude acclimatization have different physiological characteristics, was found to be compatible with the data obtained on a Sherpa subject who was studied at sea level.