Assessment of techniques used to evaluate the effect of posture and cardiac output on cerebral autoregulation.

In this study, the role of cardiac output in Cerebral Autoregulation was assessed. Mean arterial pressure, cerebral blood flow velocity (middle and anterior cerebral artery), stroke volume, cardiac output, total peripheral resistance and cerebral autoregulatory index were assessed in 3 healthy young males and 4 healthy young females during seated and upright thigh cuff testing. Two different methods (long axis left ventricular echocardiography and Modelflow) of evaluating stroke volume and cardiac output were compared. The results showed that cerebral autoregulation was less effective in the upright posture in all subjects. Females had better autoregulation in the anterior cerebral artery, whereas males had better autoregulation in the middle cerebral artery. Cardiac output does not appear to play an important role in cerebral autoregulation during thigh cuff testing. Estimations of cardiac output and stroke volume did not strongly correlate between Modeflow and long axis left ventricular echocardiography.