Detection of characteristic points of impedance cardiogram and validation using Doppler echocardiography

Impedance cardiography is a noninvasive technique for monitoring the variation in thoracic impedance during cardiac cycle. Estimation of the stroke volume and other cardiovascular indices using impedance cardiography requires error-free detection of characteristic points in the impedance cardiogram (ICG). A technique for automatic detection of ICG characteristic points using R peaks in ECG as reference is presented. It does not require pre-processing of the ICG signal for baseline correction and adjustment of detection parameters. The technique is validated using Doppler echocardiography as a reference technique, by recording ICG and ECG signals simultaneously along with velocity profile of blood flow at the level of left ventricular outflow tract. Application of the technique on the recordings from healthy subjects in pre-exercise and post-exercise conditions and from cardiac patients under rest condition showed a very low detection error.