Improved reliability of impedance cardiography by new signal processing techniques

The authors used the impedance cardiogram (ICG), the phonocardiogram (PCG), and the electrocardiogram (ECG) to determine stroke volume and systolic time intervals. Comparisons between a fully automated PC/AT-based signal processing system and a computer-assisted visual detection processing system revealed comparable means, standard errors, correlations (Spearman r), and reliability (Chronbach's alpha ) coefficients on all relevant parameters. Other analyses confirmed the utility of using Q onset to mark the beginning of ventricular systole, the B point of the ICG to denote the aortic opening, and end diastole as the reference for determining the amplitude of dZ/dt/sub mzx/.<>