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The effect of baroreflex adaptation on the dynamic cardiovascular response to head-up tilt
D G Newman1, S W White, R Callister
1Human Performance Laboratory, Discipline of Human Physiology, Faculty of Medicine and Health Sciences, University of Newcastle, NSW, Australia. davidgnewman@msn.com.au
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.