Background: Candidates to the Polish Air Force are to fulfill strict medical conditions. Every candidate, wanting to become a fighter pilot or not, has to pass a rigorous centrifuge examination. This is a costly and especially stressful process for the candidates, as first-timers. This article explores possibility for different approach to candidates fitness to fly assessment.
Methods: 14 candidates (21-22 yrs old) were subjected to a regular GOR centrifuge profile (0.1 G/s; up to +7.0 Gz; unprotected) and to lower body negative pressure (LBNP) examination (2 min. rest period followed by 3 min. at -40 mm Hg; supine position). Both, centrifuge and LBNP examinations were carried out the same day, with about 1 hour gap between them. ECG and impedance cardiography (ICG) were being recorded during both tests. The following parameters were calculated: HR and QZ (time between ventricular depolarization [beginning of the Q wave in ECG] and local maximum of the first derivative [dZ/dt] in ICG). QZ was considered to be an effective measure of dynamic heart function.
Results: +Gz tolerance for the group was +5.94 +/- 0.98 Gz. Correlation between +Gz tolerance and QZ values during LBNP test (-40 mm Hg) for all subjects was equal to r=0.6. Correlation between sets of parameters (canonical analysis) for LBNP and centrifuge was equal to r=0.78. Both results were statistically insignificant (p<0.09). Baseline HR values were 121 +/- 19 bpm and 75 +/- 12 bpm, and maximal HR values were 172 +/- 21 bpm and 81 +/- 13 bpm, respectively for centrifuge and LBNP. For both, baseline and maximal HR during LBNP and G exposure canonical correlation was equal to r=0.72. The results were statistically not significant, however.
Conclusions: Centrifuge examination is much more stressful than LBNP test. This could have implication on the objective results of centrifuge test. The results may suggest that LBNP test could be a used in pilot candidates selection, especially those presenting high baseline HR values.