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

Whole‐body impedance cardiography (ICGWB) has been proposed as a feasible means of measuring cardiac output (CO). However, the source distribution of heart‐related impedance variations in the whole body is not known. To establish how much of a signal originates in each segment of the body and what the contribution of each is to stroke volume (SV) in ICGWB, impedance in the extremities and trunk were investigated in 15 healthy volunteers. In addition, the theoretical measurement properties of ICGWB were studied using a computer model of the whole‐body anatomy as a volume conductor. The model confirmed the expected result that most of the basal impedance originates from the extremities. Clinical experiments revealed that the heart‐related amplitude variations in the ICGWB signal originate more evenly from various body segments, the trunk slightly more than the arms or legs. The heart‐related ICGWB signal represents a weighted sum of segmental pulsatile events in the body yielding physiologically meaningful data on almost the whole circulatory system.