Haemodynamic responses to varying postural stress

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°, +45°, 0°, -45°, and -90° 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° to -90°. Findings may aid responses to low and negative gravity environments