Flying experience and cardiovascular response to rapid head-up tilt in fighter pilots.
BACKGROUND
Fighter pilots report G tolerance increases with regular exposure. Our previous work has shown that the cardiovascular system of +Gz-adapted fighter pilots responds differently to orthostatic challenges than that of non-pilots. A +Gz training effect in pilots after repetitive +Gz exposure has also been shown. Individual pilot factors such as flying experience may have a role in +Gz adaptation. In this study, we investigated the relationship between flying hours (a marker of cumulative +Gz exposure) and mean arterial blood pressure (MAP) response to head-up tilt (HUT; a marker of enhanced cardiovascular performance).


METHODS
There were 14 male fighter pilots who participated: 9 had over 1000 h jet flying experience and 5 had less than 500 h. Subjects underwent rapid (approximately 4 s) +75 degrees HUT. Beat-to-beat MAP was measured noninvasively. For each subject, change in MAP from resting values was obtained for the first 30 heart beats of the HUT period. MAP responses to tilt were compared between the experienced and less experienced pilots, and the averages of the MAP deviation values were plotted against flying hours.


RESULTS
There was a strong correlation (r = 0.87, P < 0.01) between the MAP response to tilt and jet flying hours. Comparison of the MAP responses to tilt indicates that the experienced pilots increased MAP more (+8 +/- 1.7 vs 5 +/- 1.5 mmHg) and maintained MAP at a higher level during the HUT than the less experienced pilots.


CONCLUSIONS
The results suggest that flying experience in the high +Gz environment is strongly correlated with enhanced cardiovascular performance under conditions of accelerative stress.
Newman
David G
DG
Aviation Discipline, Faculty of Engineering and Industrial Sciences, Swinburne University, Melbourne, Victoria, Australia. dgnewman@swin.edu.au
Callister
Robin
R
D000054:Acceleration; D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000337:Aerospace Medicine; D001794:Blood Pressure; D006112:Gravitation; D006339:Heart Rate; D006801:Humans; D008297:Male; D018667:Tilt-Table Test