心血管系统对下体负压及立位应激反应的比较

Comparison of Responses of Human Cardiovascular System to Lower Body Negative Pressure and Orthostatic Stress

为了比较人体心血管系统在下体负压和立位耐力试验中的变化，本实验观察了１１名男性青年被试者，在阶梯式卧位下体负压（一２．７ｋＰａ、２ｍｉｎ；一４．０ｋＰａ、３ｍｉｎ，一５．３ｋＰａ、５ｍｉｎ和一６．７ｋＰａ、１０ｍｉｎ）试验和２０ｍｉｎ的立位耐力试验时的心率、血压、外周阻力、终末舒张容积、心搏量、心输出量和脑血流图等指标的变化。结果表明，两种应激试验均使回心血量减少，终末舒张容积降低，心脏处于低泵血状态，心率随负荷量增加而增加。在立位试验中，心率只在由卧位变为立位时发生一次性的明显增加，舒张压和平均动脉压的变化明显高于下体负压试验中的变化。脑血流图在两种试验中呈现相反趋势的变化。

The purpose of this experiment is to compare the effects of lower bodynegative pressure(LBNP)test with that of orthostatic(ORT ) test on the cardiovascularsystem. Heart rate ,blood pressure ,total peripheral resistance ,stroke volume ,cardiacoutput , end-diastolie volume(EDV ) and rheoencephalograms of 11 young male subjectSwere measured during incremental LBNP(一2. 7kPa、2min;一4.0kPa、3min;一5.3kPa、5min and一6.7kPa、 10min) test and 20min ORT test. The results indicatedthat EDV was decreased as a result of diminished venous return to the heart and the heartwas in a low output state during the two stress tests. But the responses of both heart rateand blood pressure were significantly different and the changes of the rheoencephalogramsin the two tests were in opposite directions.