Debski T T, Zhang Y, Jennings J R, Kamarck T W
University of Pittsburgh, Department of Psychiatry, PA 15213-2593.
Biol Psychol. 1993 Aug;36(1-2):63-74. doi: 10.1016/0301-0511(93)90081-i.
The accurate assessment of cardiac stroke volume measured by impedance cardiography depends on the reliable measurement of dZ/dtmax and the accurate detection of the relevant points on the impedance cardiogram. In one study, impedance cardiograms were collected for 75 subjects during resting conditions and during four psychologically challenging tasks, in two identical testing sessions. The reliability of stroke volumes calculated from dZ/dtmax measured from the electrical baseline and from the dZ/dt B-point on the waveforms were assessed for the two testing sessions. Consistently higher (but not statistically different) test-retest correlations were observed for the measures calculated using values of dZ/dtmax measured from the B-point. In a second study, dZ/dt waveforms with no B-point reversal from 21 subjects were scored using two alternative B-point detection algorithms: the reversal of the second derivative of delta Z and the peak of the third derivative of delta Z. Both algorithms demonstrated high reliability compared with an expert human operator. The reversal on the second derivative may better locate an inflection point on the dZ/dt signal and the third derivative may provide a good B-point estimation in the absence of any inflection point.
通过阻抗心动图测量心搏量的准确评估取决于dZ/dtmax的可靠测量以及阻抗心动图上相关点的准确检测。在一项研究中，在两个相同的测试环节中，收集了75名受试者在静息状态以及四项心理挑战性任务期间的阻抗心动图。对两个测试环节中根据从电基线测量的dZ/dtmax以及波形上的dZ/dt B点计算出的心搏量的可靠性进行了评估。对于使用从B点测量的dZ/dtmax值计算出的测量值，观察到重测相关性始终较高（但无统计学差异）。在第二项研究中，使用两种替代的B点检测算法对21名受试者无B点反转的dZ/dt波形进行评分：δZ二阶导数的反转和δZ三阶导数的峰值。与专业人工操作员相比，两种算法均显示出高可靠性。二阶导数的反转可能更好地定位dZ/dt信号上的拐点，而三阶导数可能在没有任何拐点的情况下提供良好的B点估计。
