Tilt-table testing as a predictor of + GZ tolerance

BACKGROUND: G-tolerance assessment is an essential element of both military pilot and pilot candidate evaluation.
AIMS: Attempt at prediction of individual relaxed + Gz tolerance on the basis of head-up tilt (HUT) testing.
SETTINGS AND DESIGN: In two stages, 20 healthy men at the mean age 21.5 years took part in this study. The first stage, a 45 min, HUT test was performed using the Westminster protocol. During the second stage each underwent a centrifuge evaluation in response to gradual onset rate profiles.
METHODS AND MATERIAL: In each subject, heart rate (HR) and blood pressure (BP) before and at 2, 15 and 45 min of the tilt-test were recorded. The gravity-load centrifuge (GOR) studies were carried out [following the standard GOR programme, at 0.1 G/s rate of gravity load increase until the gravity load tolerance limit (loss of peripheral vision) was reached].
STATISTICAL ANALYSIS USED: Relationships between variables were explored using Kendall′s tau-B correlation coefficient. The critical P-level was one-tailed 0.05.
RESULTS: In four of 20 subjects (20%), vasovagal syncope occurred during the tilt test. G-level tolerance of this group (of +Gz accelerations) lay in the range from +4 to +8.1 Gz, (+5.72 ? 0.86 Gz average) and was comparable to the group without syncope. Loss of consciousness did not occur in any subjects during the centrifuge test. No statistically significant correlation was observed between HR and BP during tilt test and tolerance to +Gz accelerations.
CONCLUSIONS: The result of tilt testing, carried out according to the Westminster protocol, was not useful in predicting individual tolerance to +Gz gravity loads.