下体负压作用下人心率、血压变异性谱的变化及其与心血管反应的关系

Hemodynamic Responses,Heart Rate and Blood Pressure Variability Analysis in Healthy Subjects un-der Lower Body Negative Pressure

观察了－６．６７ｋＰａ下体负压（ＬＢＮＰ）持续作用期间人心率变异性（ＨＲＶ）、血压变异性（ＳＢＰＶ）谱的变化，并探讨了谱特征与心血管反应之间的关系。结果表明：耐力良好者ＨＲＶ谱的高频峰功率（ＨＦＨＲＶ）显著降低，归一化高频参数（ＨＦＨＲＶ，ｎ）与低频参数（ＬＦＨＲＶ，ｎ）分别呈明确的降低或升高变化；ＳＢＰＶ谱的低频峰功率（ＬＦＳＢＰＶ）ＬＢＮＰ作用时降低，后又回升，至实验终止时已超出对照水平。ＬＢＮＰ作用初期，耐力不良被试者ＨＲＶ、ＳＢＰＶ谱特征的变化趋势与耐力良好者相同，但在出现晕厥前症状时，ＬＦＳＢＰＶ及ＬＦＳＢＰＶ，ｎ均有较大幅度的降低。上述结果提示：耐力不良被试者心血管反应失代偿主要与外周血管交感神经活动水平的迅速降低有关。

To elucidate the relationship between the hemodynamic responses and cardiovascular auto-nomic regulation in humans under lower body negative pressure(LBNP),10 healthy young male sub-jectS were exposed to-6.67 kPa LBNP.Seven subects were able to tolerate for 20 min, the other 3subjects had an average tolerance time of only 7.2 min. In subjects with good tolerance the base linethoracic impedance(Z。),heart rate(HR),forearm vascular resistance (FVR),normalized low frequen-cy component of heart rate variability(HRV) spectrum(LFHRV,n)and normalized low frequency com-ponent of blood pressure variability (SBPV)spectrum(LFSBPV,n)increased significantly at the onset ofLBNP and maintained at a high level during LBNP exposure,whereas stroke volume(SV),cardiacoutput(CO),forearm blood flow (FBF), high frequency component of HRV spectrum (HFHRV)andnormalized HFHRV(HFHRV,n)decreased significantly at the onset of LBNP and maintained at a low lev-el during LBNP exposure In subjects with poor tolerance,the hemodynamic responses and the charac-teristics of HRV and SBPV spectrum were similar to that noticed in good tolerant subjects at the onsetof LBNP,however,FVR and LFSBPV,n could not be maintained during LBNP exposure and declinedrapidly just before the appearance of presyncopal symptoms。These findings indicate that the unstablecardiovascular responses of the subjects with poor tolerance could be ascribed to a rapid withdrawal ofperipheral vascular sympathetic activity.