Segmental composition of whole-body impedance cardiogram estimated by computer simulations and clinical experiments

Whole-body impedance cardiography (ICG(WB)) has been proposed as a feasible means of measuring cardiac output (CO). However, the source distribution o f heart-related impedance variations in the whole body is not known. To est ablish how much of a signal originates in each segment of the body and what the contribution of each is to stroke volume (SV) in ICG(WB), impedance in the extremities and trunk were investigated in 15 healthy volunteers. In a ddition, the theoretical measurement properties of ICG(WB) were studied usi ng a computer model of the whole-body anatomy as a volume conductor. The mo del confirmed the expected result that most of the basal impedance originat es from the extremities. Clinical experiments revealed that the heart-relat ed amplitude variations in the ICG(WB) signal originate more evenly from va rious body segments, the trunk slightly more than the arms or legs. The hea rt-related ICG(WB) signal represents a weighted sum of segmental pulsatile events in the body yielding physiologically meaningful data on almost the w hole circulatory system.