Anti-G suit effect of cardiovascular dynamic changes due to +GZ stress

Lightly anesthetized dogs underwent 1-min exposure to +Gz acceleration without and with a bladder-type anti-G suit. Prior chronic instrumentation permitted through evaluation of cardiac dynamics. During +3 Gz acceleration all recorded dynamic variables were lowered and transient tachycardia occurred. After acceleration ceases, all pressures and dP/dt exceeded control levels. Inflation of the anti-G suit during +3 Gz eliminated the dramatic effects observed during and after acceleration stress. During +6 Gz with the anti-G suit inflated, arterial pressure and dP/dt were maintained whereas left ventricular end-diastolic pressure and total peripheral resistance were much elevated and heart rate was lower. At the onset of G stress, internal diameter of the heart always fell transiently. Otherwise, diameter was not significantly affected by any of the experimental conditions. The results suggest that the anti-G suit maintains perfusion pressure at high sustained G; however, with the anti-G suit inflated at +6 Gz, central venous pressure is dramatically elevated and heart rate depressed. Thus, beneficial effects which provide tolerance to high G are accompanied by potentially detrimental effects.