Status of metabolism and peripheral circulation in man during antiorthostatic hypokinesia

: Metabolism and peripheral circulation were investigated in head-down tilt tests of varying duration. The greatest changes were seen on test day 30 when the subjects showed venous hyperoxia, lower oxygen arterio-venous difference and a significant (p less than 0.05) decrease of oxygen tension in arterial blood and oxygen utilization in tissues (p less than 0.05). At the same time the subjects exhibited an increase in Pi and lactate and a maximum growth of 2,3-diphosphoglyceric acid (p less than 0.05). This exposure seems to produce a discrepancy between oxygen supply and oxygen requirements in tissues which gives rise to secondary tissue hypoxia. It is believed that the basic cause of these changes is disordered oxygen transport from blood to tissues.