[Changes in central and peripheral hemodynamics during prolonged anti-orthostatic hypokinesia as a model of...

Central and peripheral circulation was studied rheographically in 6 test subjects during a 30-day bed rest experiment and in 9 test subjects during a 49-day bed rest. The bed rested subjects were kept in a head-down position at an angle of --4 degrees. At an early stage of the experiments the cardiac output and stroke volume increased, the total peripheral resistance decreased, the tone of major regional vessels decreased and that of small vessels increased. During the 3rd-7th weeks the changes were just the opposite: cardiac output and stroke volume decreased, the total peripheral resistance increased the tone of major regional vessels increased and that of small vessels decreased. At the end of the bed rest experiment the cardiac output and stroke volume increased and the tone of regional vessels changed accordingly. Circulation parameters returned to the pretest level, at least, 3-4 weeks after the end of the best rest experiments.