Relative role of environmental and genetic factors in respiratory adaptation to high altitude

Abstract

A VARIETY of adaptive mechanisms which aid in the physiological adjustment to the hypoxic environment of altitude have been reported in man¹. Although visitors to high altitudes increase ventilation in response to environmental hypoxia, natives in the Andes and Himalayas show a blunted or absent ventilatory response to acute hypoxia both at rest and during exercise^2–5. Adult high altitude natives in the Andes have larger lungs with a greater gas exchange surface, as judged by physiological tests of lung volume and diffusing capacity, than sea level natives or short term visitors at altitude^6–9. Whether these respiratory adaptations in man are determined solely by environment or relate to genetic traits is uncertain. The age at which these pulmonary adaptations to hypoxia occur is not known, neither is it certain whether migrants to and from high altitude reversibly acquire these physiological changes. To investigate further the mechanism of pulmonary adaptations to chronic hypoxia and to clarify the position of genetic factors in this process, we undertook an expedition to Peru from April to August 1975. Control of ventilation and lung volumes were studied in different age groups, from neonatal period to adulthood, both at high altitude and sea level. It was found that the blunted ventilatory response to hypoxia and large lung volumes developed gradually after birth over a period of many years, and that the phenomena were at least partly reversible at sea level. The results showed that the adaptive response in respiratory physiology were determined by environmental rather than genetic factors.