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.


OBJECTIVE
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.


CONCLUSIONS
Baroreflex adaptation results in better performance of HR, SV and TPR in response to +Gz.
Newman
D G
DG
Human Performance Laboratory, Discipline of Human Physiology, Faculty of Medicine and Health Sciences, University of Newcastle, NSW, Australia. davidgnewman@msn.com.au
White
S W
SW
Callister
R
R
D000222:Adaptation, Physiological; D000328:Adult; D000401:Aircraft; D017704:Baroreflex / Q000502:physiology*; D006112:Gravitation; D006801:Humans; D008297:Male; D008889:Military Personnel; D013318:Stroke Volume; D018667:Tilt-Table Test; D014655:Vascular Resistance