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目的观察头低位后直立位下体负压暴露的耐力和心血管反应。方法8名被试者在下体负压倾斜床上进行“直立位-倒立位30s-直立位联合下体负压(-60mmHg)致晕厥前症状”的模拟推拉效应试验及单纯直立位+下体负压(-60mmHg)致晕厥前症状的对照试验,用阻抗法测量了试验过程中心血管功能指标的变化。结果在模拟推拉效应试验中,8名被试者出现晕厥前症状的平均耐受时间为4.5±2.4min,显著低于对照试验时的8.4±2.1min(P<0.01)。在倒立位,被试者HR较直立位基础值降低,SV和CO较直立位基础值升高,均有显著性意义。和基础值相比,直立位下体负压时HR增加的百分比显著低于对照试验(P<0.05),而直立位下体负压时SV和CO降低的百分比均显著高于对照试验时SV和CO降低的百分比(P<0.05)。在直立位下体负压暴露时,对照试验的PP和基础值比较显著降低(P<0.05),TPR比基础值显著增加(P<0.05)。结论倒立位后,再进行直立位下体负压作用,出现晕厥前症状的平均耐受时间缩短,心血管反应降低。
Objective To observe the endurance and cardiovascular response of negative pressure exposure in the upright position of the lower head. Methods Eight subjects underwent simulated push-pull effect test of “vertical position-inverted position 30s-vertical position combined with lower body negative pressure (-60mmHg) before syncope” in the lower body negative pressure tilt bed, -60mmHg) before the onset of symptoms of syncope test, measured by impedance method of cardiovascular function during the test changes. Results In the simulated push-pull effect test, the average duration of pre-syncope symptoms in the eight subjects was 4.5 ± 2.4 min, which was significantly lower than 8.4 ± 2.1 min in the control experiment (P <0.01). In the inverted position, the HR of subjects was lower than that of the upright position, and the basal values of SV and CO were higher than those of the upright position. Compared with the baseline, the percentage of HR increase in negative pressure was significantly lower than that in control (P <0.05), while the percentage of SV and CO decreased in negative pressure of upright position was significantly higher than that of control and SV Percent reduction (P <0.05). The control group showed a significant decrease in PP and basal values (P <0.05) and a significant increase in TPR (P <0.05) when compared to the baseline values under negative pressure in the upright position. Conclusion After the upside down position, the negative pressure of the lower body was increased again. The mean duration of symptoms before syncope was shortened and the cardiovascular response was decreased.