Hemodynamic response to work at simulated altitude, 4,000 m.

Abstract

Oxygen uptake, pulmonary ventilation, cardiac output (dye-dilution technique), blood pressure (intra-arterial), O2 content of arterial blood, and blood lactic acid concentration were determined in 6 men, 19-36 years of age, during submaximal and maximal work on a bicycle ergometer at sea level and after 10-60 min. exposure to PB 462 mm Hg in an altitude chamber (simulated altitude 4,000 m. 13,115 ft.). With the arterial O2 [Pa O2] satura-tion reduced from 96 to 70%, maximal O2 uptake was reduced to 72% of that at sea level, i.e., 3.46 and 2.50 1/min. respectively. Maximal values for pulmonary ventilation were 118 and 124 l./min. cardiac output 23.2 and 23.7 l./min. heart rate 184 and 186 beats/min. stroke volume 126 and 127 ml, (A-V)O2 diff 108 and 146 ml at simulated altitude and at sea level, respectively. Integrated mean arterial blood pressure was lower during work in hypoxia. At submaximal work the heart rate, cardiac output, and pulmonary ventilation were significantly elevated during hypoxia. Moderate acute hypoxia does not seem to interfere with cardiac performance or the tissues'' capability to extract O2 from the blood during exercise.