Improved body water estimation by skin-electrode interface modeling in bioimpedance spectroscopy

Multifrequency BioImpedance Analysis or BIA consists on the injection of a small limited alternating current into the human body and in the measurement of the induced impedance and phase angle from which resistance, reactance and eventually body volumes can be derived. Effective interpretation of BIA measurements requires a robust theoretical workframe. For the first time, the skin-electrode interactions are modeled. An electrical body model was developed adding to the traditional Cole-Fricke-Cole dipole a skin-electrode interface circuit. Then, this model is used to interpret raw bioimpedance measurements in order to increase the overall bioimpedance measurements accuracy from which resistance, reactance and body water volumes can be inferred. An experimental comparison between computer simulations and experimental data in a group of hemodialytic patients was performed. The final results show that higher accuracies exceeding from 100% over the traditional Cole-Fricke-Cole model can be achieved.