Haemodynamic responses to varying postural stress

Abstract

The authors present data demonstrating early cardiovascular responses to simulated gravity levels between 1G and -1G. A noninvasive, cardiac impedance cardiography system (the IQ System) was used to evaluate cardiac output (CO), stroke volume (SV), ventricular ejection time (VET), ejection fraction (EF), and pre-ejection period (PEP). Seven subjects were positioned at selected angles of +90/spl deg/, +45/spl deg/, 0/spl deg/, -45/spl deg/, and -90/spl deg/ for five minutes at each angle. These postural changes simulate different gravitational forces on the human body ranging from +1G to -1G. This study's findings demonstrate an overall increasing trend in CO, SV, VET and EF, and a slight decrease in PEP with postural changes from +90/spl deg/ to -90/spl deg/. Findings may aid responses to low and negative gravity environments.<>