An overview of the impedance models of the thorax and the origin of the impedance cardiography signal for modelling of the impedance signals

This paper presents our work in the search for a realistic thorax impedance model that is suitable for the simulation of an impedance cardiography (ICG) signal model. The developed ICG signal model would be useful to evaluate the performance of e.g. algorithms for the separation of cardiac and respiratory signals. Five different impedance models of the thorax were studied to evaluate their suitability with respect to the development of the ICG signal model. We found out that none of the models would be accurate enough to imitate the real human thorax phenomena in the context of ICG. In addition, we also reviewed the generation of (bio-) impedance signal in order to understand the origin of the ICG signal waveform. It is found that although a consensus exists in the scientific community, several researchers have expressed doubts about the generally admitted origin of impedance signal waveform. The present study concludes that the ICG signal model could be mathematically derived from measured electrical bio-impedance (EBI) data obtained with a specific electrodes configuration.