Higher arterial oxygen saturation during submaximal exercise in Bolivian Aymara compared to European sojourners and Europeans born and raised at highaltitude

Arterial oxygen saturation (SaO(2)) was measured at 3,600-3,850 m by pulse oximetry at rest and during submaximal exercise in three study groups: 1) h ighland Aymara natives of the Bolivian altiplano (n = 25); 2) lowland Europ ean/North American sojourners to the highlands with at least 2 months of ac climatization time to 3,600 m (n = 27); and 3) subjects of European ancestr y born and raised at 3,600 m (n = 22). Aymara subjects maintained similar t o 1 percentage point higher SaO(2) during submaximal work up to 70% of thei r maximal work capacity, and showed a smaller rate of decline in SaO(2) wit h increasing work compared to both European study groups. The higher-exerci se SaO(2) of Aymara compared to Europeans born and raised at 3,600 m sugges ts genetic adaptation. The two European study groups, who differed by expos ure to high altitude during their growth and development period, did not sh ow any significant difference in either resting or exercise SaO(2). This su ggests that the developmental mode of adaptation is less important than the genetic mode of adaptation in determining exercise SaO(2). A weak correlat ion was detected (across study groups only) between the residual forced vit al capacity (FVC) and the residual SaO(2) measured at the highest level of submaximal work output (P = 0.024, R = 0.26). While firm conclusions based on this correlation are problematic, it is suggested that a part of the hig her SaO(2) observed in Aymara natives is due to a larger lung volume and pu lmonary diffusion capacity for oxygen. Results from this study are compared to similar studies conducted with Tibetan natives, and are interpreted in light of recent quantitative genetic analyses conducted in both the Andes a nd Himalayas. (C) 2000 Wiley-Liss, Inc.