Journal of Applied Physiology, Vol 38, Issue 6 1143-1145, Copyright © 1975 by American Physiological Society
Comparison of of techniques for measuring +Gz tolerance in man
R. W. Krutz Jr, S. A. Rositano and R. E. Mancini
Two objective methods and one subjective method for measuring +Gz tolerance
(inertial vector in a head-to-foot direction) were compared on the human
centrifuge. Direct eye-level blood pressure (Pa), blood flow velocity in
the superficial temporal artery (Qta), and subjective visual symptoms were
used to determine tolerance to rapid onset acceleration (1 G/s) on the
USAFSAM human centrifuge. Seven "relaxed" subjects with extensive
centrifuge experience were exposed to gradually increasing +Gz plateaus
until the subject reported 100% loss of peripheral centrifuge gondola
lights (PLL) and 50% loss of central light (CLD); viz., blackout. Zero
forward Qta occurred 6 s (range 4-9 s) before subjective blackout and when
mean eye-level blood pressure had reached 20 +/- 1 mmHg (SE). The results
of this study indicate that flow changes in the superficial temporal artery
reflect flow changes in the retinal circulation during +Gz stress.
