A new proposal of optimal spot-electrode array for electrical impedance cardiography through the measurement of thoracic impedance mapping

An optimal spot-electrode array for electrical impedance or admittance cardiography to estimate stroke volume(SV) was determined based on the measurement of contour maps of static(Z₀) and pulsatile components(ΔZ) of the thoracic impedance using a 32×2 channels impedance mapping system. Taking a necessary condition of two-compartment coaxial cylinder model of the thorax to calculate SV into consideration, i.e., uniformity of Z₀-map and ΔZ-maps during cardiac blood ejection cycle, a pair of spot-electrodes for current injection should be located as far from the thorax as possible, such as on the forehead and on the left medial knee, while those for voltage pick-up would be appropriate to place on the medial portion at the level of clavicle and on the portion above the xiphisternum, where the ΔZ waves due to pulmonary circulation as well as blood ejection contracted by the heart showed little. Comparison experiments between the impedance and an indicator dilution method were also made to evaluate this newly determined spot-electrode array.