Impedance Cardiography Signal Processing with Savitzky-Golay and Frequency Sampling Kernels

ICG (impedance cardiography) is in addition to ECG (electrocardiography) an important indicator of the functioning of the overall cardiovascular system, including the cardiac (heart) activity. Usage of the ICG, especially in the wearables, improves the health monitoring, as the ICG shows various important hemodynamic parameters (relevant time intervals, also the stroke volume and cardiac output and their variability). ICG waveform is the time-domain derivative of the electrical bio-impedance signal. Two possible sampled data differentiation algorithms are discussed in the paper and demonstrated on the real-life signals, one exploiting the Savitzky-Golay 1-st order differentiation numerical scheme and another the frequency sampling method based FIR-filter design. Both approaches are shown to be promising. Tuning and final evaluation of the superiority of one or another method needs more experimental data and research.