Lead field theoretical approach in impedance cardiography using 3-D finite difference element modelling

Impedance cardiography (ICG) offers a simple and unobstructive method of determining cardiac stroke volume based on the measurement of conductivity changes at body surface. ICG has not achieved wide clinical acceptance despite its advantages since its theoretical basis and interpretation of the measurement data remain controversial and questionable. Several ICG measurement configurations and systems have been suggested over the years for convenience or improved performance. Derived methods have been empirical and the origin of signal still remains unknown. Recently, researchers have become increasingly interested in the analysis of ICG using numerical computer modelling techniques. This, however, has generally not lead to more sophisticated or reliable knowledge of ICG. This study was conducted to demonstrate the potentiality of the lead field and reciprocity theoretical approach in ICG analysis. Methods have generally not been applied in analyzing measurement sensitivities of ICG techniques even though they are extremely powerful and practical to employ. With lead field and reciprocity method contributions from all sources are taken into account in a single simulation. Distribution of signal origins of basal impedance is obtained without approximations of quantitative changes occurring in the thorax. This approach can be employed to determine measurement sensitivity of any impedance measurement system