Stroke volume estimation in heart failure patients using bioimpedance: a realistic simulation of the forward problem

Bioimpedance techniques may be appropriate for cardiac stroke volume (SV) monitoring since thoracic anatomical changes during the heart contraction reflect on the conductivity distribution. In some bioimpedance techniques, the electrical potential is calculated from the impedance distribution using Poisson's equation. That is called the forward problem and in many applications it is used inherently in the solution of the inverse problem -- finding the impedance distribution from the electrical potentials. In this work, the forward problem was simulated using a realistic 3D hybrid phantom of the human thorax. The cardiac cycle of normal patients and patients suffering from cardiogenic pulmonary edema was simulated, including the effect of pulmonary blood perfusion during heart contraction. The forward problem was found to be most sensitive to SV when current was injected from the right breast toward the left scapula (-0.021 microV ml(-1)). Our simulations show that both the heart volume and lung conductivity affect the developing voltage; therefore in SV estimation, the lung conductivity and heart volume should be jointly estimated.