Abstract
Five young male subjects were exposed to simulated altitudes of 0 m (sea level), 2, 000 m and 4, 000 m in a hypobaric chamber under ambient temperatures of 16°C, 20°C, 24°C and 28°C. Oxygen uptake (Vo2), cardiac output (Q ; CO2 rebreathing method), arteriovenous O2 difference (AVOD), heart rate (HR), and stroke volume (SV) were measured during two successive submaximal exercises after 2 hours of exposure. VO2 and SV at high altitudes were similar to those at sea level. Q and HR at a given VO2 Significantly increased at high altitudes, and AVOD decreased at high altitudes. No effect of ambient temperature on Q and AVOD was found, but HR showed a combined effect of temperature and altitude : at sea level and at an altitude of 2, 000 m, HR tended to increase when temperature increased ; but at an altitude of 4, 000 m, HR at low temperature was equal to the level at high temperature. These results indicated the possibility of vasodilation in the peripheral region even at low ambient temperature at high altitudes.
