Peripheral arterial vascular function at altitude: sea-level natives versus Himalayan high-altitude natives

Objectives Regulation of the vascular system may limit physical performance and contribute to adaptation to high altitude. We evaluated vascular funct ion in 10 Himalayan high-altitude natives and 10 recently acclimatized sea- level natives at an altitude of 5050 m. Methods We registered electrocardiogram, blood flow velocity in the common femoral artery, and blood pressure in the radial artery using non-invasive methods under baseline conditions, and during maximal vasodilation after 2 min leg occlusion, Vascular mechanics were characterized by estimating puls e wave Velocity and input impedance. Results Pulse wave velocity and parameters of input impedance did not diffe r between groups under baseline conditions. In the post-ischemic period, th e ratio between maximal hyperemic and baseline blood flow velocity was sign ificantly higher in the high-altitude than in the sea-level natives (5.7 +/ - 2.5 versus 3.8 +/- 1.2, P < 0.05). The leg vascular resistance decreased in the post-occlusive period without differences between groups. Characteri stic impedance decreased in the post-ischemic period by about one third of the baseline level without differences between groups. The post-ischemic de crease of input impedance modulus was more marked in the high-attitude than in the sea-level natives at low frequencies (28 +/- 12 versus 6.4 +/- 20% at 2 Hz, P < 0.01). Conclusions Our results demonstrate a superior ability to increase blood fl ow velocity as a response to muscular ischemia in high-altitude natives com pared to sea-level natives. This phenomenon may be associated with a more e ffective coupling between blood pressure and blood flow which is probably c aused by differences in conduit vessel function. (C) 2001 Lippincott Willia ms & Wilkins.