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

Abstract

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 0, 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) ofollaque, 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 (VE, Umin, BTPS) oxygen consumption (V02, STPD), heart rate (bpm), steady-state diffusion capacity (DLCO, cddtorr), and hemoglobin (Hgb, gm/dl) were made. Vital capacities were 5.1 t 0.1 1 (BTPS) while DLCO's were 36.9 ? 2.6 cddtorr. Hemoglobin values were 18.3 ? 0.4 gm/dl. Isocapnic HVR' s were -0.17 2 0.05 (VE ltmid BTPS/SaO,, %), During steady-state exercise at 600 kpdmin subjects reached a V02 of 1.7 2 0.1 Urnin, aventilatory equivalent (VENO,) of33.2 IfI 1.02, aDLCO of 71.2 t 4.5 cddtorr with heart rates of 169.6 t 6.8 bpm, and an SaO, of 84.74 2 2.8%. At maximum exercise there was no subsequent arterial oxygen desaturation (SaO, = 87.0 t 1.0%) while VEN0,'s were increased to 44.5 2 3.4 with a VO, of 2.3 2 0.3 Urnin 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.Human populations who live at high altitude undergo a number of adaptations that allow them to survive in h poxic environments (Frisancho, 1975; Bager, 1978; Win-sion gradient for oxygen at each subsequent interphase. Furthermore, since survival depends on an adequate oxy en supply to the nisms must take place to compensate for the lower ambient oxygen partial ressure. A system which include: ventilation of air to and from the lungs, matching of that air with blood flow in the capillaries of the lungs, diffusion of oxygen from the gas to the blood phase, circulation of the blood by the heart tissues at all times, crucia B adaptive mechanumber of components make up t R is delivery and the vasculature to the body's tissues, diffusion of oxygen from the blood to the cell c oplasm, and the utilization of oxygen inThe topics of the development of body and lung growth at high altitude, the alterations in hem0 lobin and red blood cells, and the red blood cell production will be covered by other authors in this symposium. This paper will, therefore, concentrate primarily on the acute and chronic ventilatory responses to high altitude and diffusion of oxygen from the air to the blood during rest and exercise. It was the purpose of this study to compare these responses in the high altitude natives t T e mitochondria of the cell. rel...

Exercise performance of Tibetan and Han adolescents at altitudes of 3,417 and 4,300 m

“…Consistent with the observations made by others (28,38), we noted that the Tibetans maintained significantly higher Sa O 2 values during maximal exercise at high altitude than did the Hans, suggesting that the Tibetans have higher diffusing capacity compared with the Hans. Schoene et al (28) reported that highaltitude natives attained high levels of exercise with a ventilatory response to exercise that was comparable to or lower than that achieved by lowlanders who exercised at workloads comparable to highlanders with acute hypoxia.…”

“…Schoene et al (28) reported that highaltitude natives attained high levels of exercise with a ventilatory response to exercise that was comparable to or lower than that achieved by lowlanders who exercised at workloads comparable to highlanders with acute hypoxia. The lowlanders demonstrated a marked decrease in Sa O 2 during exercise.…”

Pulmonary gas exchange at maximal exercise in Danish lowlanders during 8 wk of acclimatization to 4,100 m and in high-altitude Aymara natives

“…chronic hypoxia; acute normoxia; ventilation HIGH-ALTITUDE NATIVES from North America (8), Tibet (27), and South America (19,25) have unique pulmonary gas transport abilities, maintaining low alveolar-arterial PO 2 difference (A-aPO 2 ) at maximum exercise, thus preserving arterial PO 2 (Pa O 2 ) and saturation (Sa O 2 ). This confers a clear advantage to high-altitude natives compared with the lowlanders during exercise at altitude.…”

Ancestry explains the blunted ventilatory response to sustained hypoxia and lower exercise ventilation of Quechua altitude natives

“…3) and VE/V O 2 (P ϭ 0.013) measured at altitude compared with subjects with relatively high EAP (Ͼ0.35) and low NAAP (Ͻ0.65). Thus Quechua ancestry may be partly responsible for the well-known blunted HVR (10,35,36,57,62) and the relative exercise hypoventilation at altitude (7,32,55,66) of Andeans compared with European controls. From the novel study design, we infer both a population genetic basis and an evolutionary origin for these trait differences.…”

“…The sustained vs. acute response has not been systematically evaluated in Andean highland natives, but groups from this region appear to have a lower or "blunted" acute HVR and a lower effective alveolar ventilation compared with high altitude (HA)-acclimatized control groups from the lowlands (10,35,36,43,57,61,62). Andeans also have lower VE during exercise at HA compared with acclimatized lowland controls (7,32,55,66). These traits may be unique to Andeans, as many studies show normal HVR and higher VE in natives of the Himalayan plateau (2,21,25,29,75).…”