RESUMO
Hypoxic and exercises ventilatory responses measured in Tibetan who lived at moderate (2000-3000m, M-Tibetan) and high (4000-4700m, H-Tibetan) altitude areas. The result showed that the slope of hypoxic ventilatory response (HVR; VE/SaO2) in M- and H-Tibetan was 0.81 +/- 0.07 and 0.46 +/- 0.04 L/min/%SaO2 (P < 0.01) and the maximal exercise ventilation (VEmax) was 78.3 +/- 3.5 and 68.2 +/- 2.1 L/min (P < 0.05), respectively. There were positive correlation between delta VE/delta SaO2 and VEmax, which gamma = 47.0 +/- 37.3x, r = 0.70 in M-Tibetan, and gamma = 53.8 +/- 31.4x, r = 0.67 in H-Tibetan. Maximal heart rate of the H-Tibetan was significantly lower than that in the M-Tibetan (P < 0.01). It is suggested that the attenuation of HVR depends on the magnitude of the hypoxic stimulus. Therefore, there are differences even among the high-altitude natives in ventilatory response to hypoxia, e.g. normal respiratory sensitivity to hypoxia in moderate-altitude natives, and blunted in high-altitude natives.