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Decreased +gz tolerance following lower body positive pressure: simulated push-pull effect
W X Zhang1, C L Zhan, X C Geng
15th Department, Institute of Aviation Medicine, Air Force, PLA, China. zhangwuxing@263.net
Objective:
The purpose of this study was to attempt to simulate the push-pull maneuver on a single-axis human centrifuge using lower body positive pressure (LBPP), and to observe the effect of the push-pull maneuver on +Gz tolerance.
Methods:
Six volunteers participated in the experiment. They were subjected to LBPP of up to 300 mm Hg for 1 min. Blood pressure (BP) and heart rate (HR) were monitored before, during and after LBPP. Immediately after LBPP, +Gz tolerance was measured on a human centrifuge.
Results:
During LBPP, systolic BP (SBP) and diastolic BP (DBP) increased significantly, mean arterial pressure (MAP) increased but not significantly, and HR decreased significantly. After LBPP, SBP and MAP decreased significantly, while DBP and HR decreased but not significantly. In all subjects, +Gz tolerance decreased after LBPP. The decreased value was 0.70 +/- 0.06 G, maximum 1.0 G and minimum 0.5 G.
Conclusion:
The push-pull maneuver can be simulated on a single-axis human centrifuge using LBPP. The physiologic effects of LBPP were similar to those of -Gz. We observed that +Gz tolerance decreased after LBPP, which confirmed the push-pull effect from the experiment.