Horstmann E, Könn B
Knappschaftskrankenhaus, University of Bochum, Germany.
Med Prog Technol. 1993;19(4):173-8.
Previous investigators demonstrated divergent results, when comparing impedance to other established methods for the assessment of cardiac output. Cardiac output is defined as stroke volume multiplied by heart rate. Heart rate is easy to measure and the main determinant of cardiac output during exercise under physiologic conditions. Therefore, cardiac output (CO) by tetrapolar impedance cardiography (TIC) was compared to thermodilution (TD) in 35 patients (P). In a second step it was examined how heart rate alone would perform as a predictor of CO under exercise. Measurements were done at rest, 25, 50, 75, and 100 w. Results were corrected for hematocrit (HCT). There was no correlation between CO by TD and by TIC at rest (r = -0.006). Under exercise correlation was somewhat better with r = 0.45 despite correction for HCT. Mean values were similar, but scatter was wide. Relative increase in CO by both methods was also correlated (r = 0.46), while heart rate alone correlated best to TD (r = 0.65). Transthoracic impedance cardiography is not a reliable technique to measure absolute values of cardiac output at rest. During exercise large scatter limits this method to the measurement of CO in larger groups. At exercise heart rate alone appears to be a better indicator of increase of cardiac output than impedance cardiography.
先前的研究人员在将阻抗与其他已确立的心输出量评估方法进行比较时，得到了不同的结果。心输出量定义为每搏输出量乘以心率。心率易于测量，且在生理条件下运动时是心输出量的主要决定因素。因此，在35名患者中，将四极阻抗心动图（TIC）测得的心输出量与热稀释法（TD）测得的心输出量进行了比较。第二步，研究了仅心率作为运动时心输出量预测指标的表现。测量在静息状态、25瓦、50瓦、75瓦和100瓦功率下进行。结果根据血细胞比容（HCT）进行了校正。静息时，TD法和TIC法测得的心输出量之间无相关性（r = -0.006）。运动时，尽管校正了HCT，但相关性有所改善，r = 0.45。平均值相似，但离散度较大。两种方法测得的心输出量相对增加也具有相关性（r = 0.46），而仅心率与TD法的相关性最佳（r = 0.65）。经胸阻抗心动图不是测量静息时心输出量绝对值的可靠技术。运动时，较大的离散度限制了该方法在较大群体中测量心输出量的应用。在运动时，仅心率似乎比阻抗心动图更能作为心输出量增加的指标。
