Increased diffusion capacity maintains arterial saturation during exercise in the Quechua Indians of Chilean Altiplano

The majority of Quechua Indians of the Altiplano of Northern Chile spend their lives between 3,500 and 4,500 meters, while some work as miners at much higher altitudes. In order to gain insight into the factors of O 2 transfer in the lung that permit them to live and work in this hypoxic environment, we studied 20 male Quechuas (26.2 ± 1.1 years) of Ollaque, Chile, at 3,900 meters (barometric pressure = 490 torr). Resting pulmonary function and hypoxic ventilatory response (HVR) tests were done. Progressive exercise to exhaustion on a cycle ergometer was performed, and measurements of ventilation (V E , l/min, BTPS) oxygen consumption (VO 2 , STPD), heart rate (bpm), steady‐state diffusion capacity (DLCO, cc/m/torr), and hemoglobin (Hgb, gm/dl) were made. Vital capacities were 5.1 ± 0.1 1 (BTPS) while DLCO's were 36.9 ± 2.6 cc/m/torr. Hemoglobin values were 18.3 ± 0.4 gm/dl. Isocapnic HVR's were −0.17 ± 0.05 (V E l/min/BTPS/SaO 2 , %). During steady‐state exercise at 600 kpm/min subjects reached a VO 2 of 1.7 ± 0.1 l/min, a ventilatory equivalent (VE/VO 2 ) of 33.2 ± 1.02, a DLCO of 71.2 ± 4.5 cc/m/torr with heart rates of 169.6 ± 6.8 bpm, and an SaO 2 of 84.74 ± 2.8%. At maximum exercise there was no subsequent arterial oxygen desaturation (SaO 2 = 87.0 ± 1.0%) while VE/VO 2 's were increased to 44.5 ± 3.4 with a VO 2 of 2.3 ± 0.3 l/min or 43.8 ± 9.5 cc/kg/min. The ventilatory responses are similar to those of lowlanders exposed to comparable hypoxia during exercise (Schoene et al., Fed. Proc. 42 : 978, 1983) but the DLCOs are significantly higher. We conclude that high‐altitude natives of the Andes maintain arterial oxygen saturation during exercise because of an increased diffusion capacity for oxygen at the lung.