The effect of baroreflex adaptation on the dynamic cardiovascular response to head-up tilt

Background: Baroreflex adaptation to repetitive +Gz has been reported previously. The underlying mechanism may involve different responses of stroke volume (SV) and total peripheral resistance (TPR) to +Gz. Hypothesis: The previously observed enhanced mean arterial pressure (MAP) regulation in fighter pilots (FP) is mediated by increases in SV and/or TPR. Methods: There were 8 pilots and 12 non-pilots who underwent head-up tilt. SV was determined using impedance cardiography. Results: MAP increased significantly in FP, due to heart rate (HR) and TPR increasing more and SV decreasing less. Conclusion: Baroreflex adaptation results in better performance of HR, SV and TPR in response to +Gz.