Ventilation and the control of erythropoiesis in high-altitude natives of Chile and Nepal.

Abstract

AbstractPrevious studies have suggested that the hematocrit and hemoglobin values in Himalayan natives (Sherpas) are lower than those of Andean natives (Quechua Indians) living at the same altitude, perhaps because of genetic differences. To study these populations further, we selected healthy male subjects in Ollagüe, Chile (n = 29, age = 27.3 ± 15.9 years), and in Khunde, Nepal (n = 30, age = 24.7 ± 13.8 years). Both of these villages are located at 3,700 m above sea level. Hematologic measurements confirmed lower hematocrit values in Nepal (48.4 ± 1 4.5%) than in Chile (52.2 ± 1 4.6%) (P < 0.003). When subjects were matched for hematocrit, erythropoietin concentrations in Chile were higher than in Nepal (P < 0.01).To investigate a possible link between ventilation and erythropoiesis, we studied the ventilatory response to hypoxia in Sherpas with differing hematocrits. Our subjects could be classified as “responders” or “nonresponders” with respect to their pattern of ventilation after inspiration of 1 or 2 breaths of N2. The responders had significantly (P < 0.02) lower hematocrits (mean 46.6 ± 3.0%) than the nonresponders (mean 52.4 ± 5.0%), suggesting that ventilatory sensitivity to hypoxia may play a role in determining the hematocrit in these subjects.