de Mey C, Enterling D
Methods Find Exp Clin Pharmacol. 1986 Jul;8(7):449-57.
The hemodynamic response to passive upright tilt in thirty-five normal subjects was assessed by combined electrocardiography, differentiated electrical impedance cardiography, phonocardiography and non-invasive blood pressure measurement. The increase in transthoracic impedance and decrease in estimated stroke volume were accompanied by a cardio-acceleratory and vasopressor response. The increase in heart rate did not compensate for the decrease in estimated stroke volume and the estimated cardiac output decreased. Diastolic and mean blood pressure, however, increased. The relative systolic time interval was largely increased. Most of these changes returned to base-line on resuming the supine position. This test procedure and the non-invasive methods used offered a suitable setting for the within-subject assessment of postural changes in cardiovascular function. Certain methodological aspects were found to affect the interpretation of the impedance cardiographic data. Pre-systolic low amplitude-high velocity changes in transthoracic impedance, especially when occurring in conditions where strict respiratory control cannot be sustained, can complicate the delineation of the systolic time intervals and the correction of respiration-related fluctuations in the signal's base-line. One further subject is presented with imminent syncope on tilting, in order to highlight this intrinsic but unpredictable morbidity as a limiting factor in the application of this study procedure.
通过联合心电图、微分电阻抗心动图、心音图和无创血压测量，评估了35名正常受试者对被动直立倾斜的血流动力学反应。经胸阻抗增加和估计的每搏量减少伴随着心脏加速和血管加压反应。心率增加并不能补偿估计的每搏量减少，估计的心输出量下降。然而，舒张压和平均血压升高。相对收缩期时间间隔大幅增加。恢复仰卧位后，这些变化大多恢复到基线水平。该测试程序和所使用的无创方法为受试者心血管功能姿势变化的评估提供了合适的环境。发现某些方法学方面会影响阻抗心动图数据的解释。经胸阻抗在收缩前期出现的低幅度-高速变化，尤其是在无法维持严格呼吸控制的情况下发生时，会使收缩期时间间隔的描绘以及信号基线中与呼吸相关波动的校正变得复杂。还介绍了另一名受试者，其在倾斜时即将发生晕厥，以突出这种内在但不可预测的发病率作为该研究程序应用中的一个限制因素。
