Sherwood A, Carter L S, Murphy C A
Department of Psychiatry, University of North Carolina, Chapel Hill 27599.
Aviat Space Environ Med. 1991 Feb;62(2):116-22.
One critical component of the Kubicek (8) stroke volume equation, used to measure cardiac output by impedance cardiography, is dZ/dt(max). The present study, conducted on six anesthetized dogs, compared impedance cardiac output derived using two alternative methods of quantifying dZ/dt(max), with simultaneous thermodilution measures. Values for dZ/dt(max) quantified relative to dZ/dt = 0 baseline and relative to the dZ/dt B-point were entered into the Kubicek equation to generate cardiac output measures designated as impedance-A and impedance-B, respectively. Emphasis was placed upon evaluating impedance cardiac output within its accepted limits as a relative change measure. Systematic alterations in cardiac output were produced by intravenously administered isoproterenol, phenylephrine and nitroprusside. Drug-induced changes in cardiac output measured by the impedance-A method were statistically identical to thermodilution. For the impedance-B method, similarity to thermodilution was limited to two of the three drug conditions. Correlations of impedance cardiac output with thermodilution tended to be higher for the impedance-A method. Together with theoretical and practical considerations, these results support quantification of dZ/dt(max) relative to dZ/dt = 0 when used in the Kubicek stroke volume equation.
用于通过阻抗心动描记法测量心输出量的 Kubicek（8）每搏输出量方程的一个关键组成部分是 dZ/dt(max)。本研究对六只麻醉犬进行，比较了使用两种替代方法量化 dZ/dt(max)得出的阻抗心输出量与同时进行的热稀释测量结果。相对于 dZ/dt = 0 基线和相对于 dZ/dt B 点量化的 dZ/dt(max)值被代入 Kubicek 方程，分别生成指定为阻抗 -A 和阻抗 -B 的心输出量测量值。重点在于评估在其可接受范围内作为相对变化测量值的阻抗心输出量。通过静脉注射异丙肾上腺素﹑去氧肾上腺素和硝普钠产生心输出量的系统性改变。通过阻抗 -A 方法测量的药物诱导的心输出量变化与热稀释在统计学上相同。对于阻抗 -B 方法，与热稀释的相似性仅限于三种药物条件中的两种。阻抗心输出量与热稀释的相关性对于阻抗 -A 方法往往更高。结合理论和实际考虑，这些结果支持在 Kubicek 每搏输出量方程中使用时相对于 dZ/dt = 0 量化 dZ/dt(max)。
