HYPOXIC VENTILATORY RESPONSES IN TIBETAN RESIDENTS OF 4400 M COMPARED WITH 3658 M

Lifelong Tibetan residents of 3658 m ventilate as much and have hypoxic and hypercapnic ventilatory responsiveness as least as great as acclimatized newcomers, and likely greater than lifelong North or South American high-altitude residents. To determine whether Tibetans residing at altitudes > 3658 m maintained similar levels of ventilation, hypoxic and hypercapnic ventilatory responses, we transported 20 lifelong residents of greater than or equal to 4400 m to 3658m for comparison with 27 similarly-aged male Tibetan residents of 3658 m. At 3658 m, the 4400 m compared with the 3658 m Tibetans had similar levels of minute ventilation and arterial O-2 saturation, higher respiratory quotients but lower hypoxic ventilatory responses. We concluded that Tibetan residents of greater than or equal to 4400 m ventilate as much as Tibetan residents of 3658 m despite an altitude-associated blunting of their hypoxic ventilatory responses. Thus, factors other than hypoxic ventilatory chemosensitivity are likely to be important contributors to resting ventilation among Tibetan high altitude residents.