下体负压联合旋转床模拟推拉效应的心率变化特征

Study on the changes of heart rate during "push-pull effect" simulation using a tilt table combined with a lower body negative pressure device

目的建立下体负压联合旋转床模拟推拉效应的方法,观察不同预先-Gz作用后Gz时心率反应的变化特征。方法8名健康男性志愿者,利用旋转床或联合下体负压随机暴露于预先0°(0Gz)、-30°(-0.5Gz)和-90°(-1Gz),分析在模拟推拉动作时-Gz或0Gz、"拉"时相及与单纯+1Gz时相同时间段的平均心率,比较在不同倾斜角度即不同预先-Gz作用或联合下体负压模拟推拉动作时"拉"时相的心率反应。结果利用旋转床模拟推拉动作时,在"推"时相即头低位时心率显著降低,随倾斜角度的增大降低更加显著,"拉"时相的心率随预先倾斜角度增大回升更明显。下体负压联合旋转床模拟推拉动作时,心率变化与单纯旋转床模拟推拉动作时基本一致。后者在"拉"时相与单纯+1Gz作用时相比心率变化更大,提示心率回升更加缓慢。结论旋转床或联合下体负压可以模拟推拉效应,其心率反应随预先-Gz值的增大在"拉"时相回升明显,并且受随后模拟+Gz负荷大小的影响。

Objective To set up a model simulating ＂push-pull effect＂ （PPE）, and observe the changes of heart rate （HR） in the course of experiment. Methods Eight young male volunteers served as subjects. They underwent 3 profiles of simulated PPE on the tilt table respectively with or without lower body negative pressure （LBNP） as follows： ① ＋90° 30 s （＋1 Gx）→0° 15 s （0 Gx）→ ＋90° 30 s （＋1 Gx）; ② ＋90° 30 s （＋1 Gx）→-30° 15 s（-0.5 Gx）→ ＋90°30 s （＋1 Gx） ;③→ ＋90° 30 s （＋1 Gx）→-90° 15 s （-1 Gx）→ ＋90° 30 s （＋1 Gx）. In case of using LBNPdevice, negative pressure （-70 mm Hg） was applied within 3 s when subject was turned to ＋ 90° position from 0 Gx or -Gx. Electrocardiograms were recorded during the experiment for observation of change of HR. Results HR during push phase （head-down tilt, HDT） with or without combining with LBNP decreased significantly along with the increase of HDT angle, and so did the rise again of HR during the pull phase （ turned to ＋ 90°）. In case of combining with LBNP, the restore of HR during pull phase was significantly slower than that without LBNP. Conclusions Tilt table combined with LBNP device can be used to simulate the push-pull effect. LBNP can be used to exaggerate the effect of ＂pull＂.