Sources of the thoracic cardiogenic electrical impedance signal as determined by a model

A three-dimensional electrical model was developed to study the origin of ΔZ due to cardiac activity recorded from band electrodes around the neck and lower thorax. Volume changes were simulated with resistivity changes in the lungs, large arteries, large veins and atria, ventricles, small arteries and veins and the skeletal muscle for a typical 80 ml ventricular stroke volume. The results showed the contributions to ΔZ to be 61 per cent from the lungs, 23 per cent from the large arteries and 13 per cent from the skeletal muscle. The ΔZ signal was most sensitive to skeletal muscle volume change The results indicate that the ΔZ signal has many origins which could cause significant error in calculated cardiac function it all the regions do not change in the normal related pattern.