CARDIAC OUTPUT IN HYPEROXIA, NORMOXIA AND HYPOXIA

Abstract

816 We examined the hypothesis that maximal cardiac output (COmax) does not differ between acute hyperoxia, normoxia and hypoxia. Six male endurance athletes were measured at rest and during progressive cycling in hyperoxia (Fraction of oxygen in inspired air, F1O2, 0.30), normoxia (F1O2 0.21) and hypoxia (F1O2 0.15). The subjects started cycling at 0 W and the power was increased by 100 W in 5-minute intervals until exhaustion. CO was measured with an acetylene rebreathing method at the end of each workload. V̇O2 was measured breath-by-breath. Maximal power, V̇O2max, COmax, maximal stroke volume (SVmax) and heart rate (HRmax) as well as COmax/V̇O2max-ratio were affected by F1O2(table).TableOur results indicate that maximal cardiac output is significantly diminished along with V̇O2max and maximal exercise performance in acute hypoxia. The diminished COmax in hypoxia is affected both by decreased maximal stroke volume and heart rate. In hyperoxia, COmax increased only slightly despite a greater increase in V̇O2max.