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SummaryParasitic capacitances and high‐residual impedances (typical of electrode/tissue interfaces) have significant effects on estimated electrical impedances of tissues under study. This leads to deviations (especially at high frequency) from the true tissue impedance. This work outlines the circuit theory describing estimation errors occurring when one and two parasitic capacitances are present in tetrapolar electrode configurations typical for bioimpedance measurements. The described circuit theory was validated using both simulations and measurements of a fabricated printed circuit board that implemented the tetra‐polar model. Using the presented model, correction procedures using (a) measurements of the source and sink excitation currents and (b) averaging measurements of forward and reverse electrode configurations have been validated in simulation showing reductions in the estimation errors at frequencies greater than 1 MHz.

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Recent advances in commercially available integrated complex impedance spectroscopy controllers have brought rapid increases in the quality of systems available to researchers for wearable and remote patient monitoring applications. As a result, novel sensing methods and electrode configurations are increasingly viable, particularly for low-power embedded sensors and controllers for general electrochemical analysis. This study evaluates a case study of the four electrode locations suitable for wearable monitoring of respiratory and heart activity monitoring using complex impedance spectroscopy. We use tetrapolar electrode configurations with ten stimulation frequencies to characterize the relative differences in measurement sensitivity. Measurements are performed and compared for the magnitude, phase, resistive, and reactive components of the bioimpedance using two COTS-based controllers, the TI AFE4300 and MAX30009. We identify the highest percent relative changes in the magnitude of the impedance corresponding to deep breathing and heart activity across the chest (17% at 64 kHz, 0.5% at 256 kHz, respectively), on the forearm (0.098% at 16 kHz, 0.04% at 8 kHz), wrist-to-wrist across the body (0.28% at 256 kHz, 0.04% at 256 kHz, respectively), and wrist-to-finger across the body (0.35% at 4 kHz, 0.05% at 4 kHz, respectively). We demonstrate that the wrist-to-wrist and wrist-to-finger configurations are most promising and may enable new wearable bioimpedance applications. Additionally, this paper demonstrates that deep respiration and heart activity influence bioimpedance measurements in whole-body measurement configurations, with variations of nearly 1% in measured impedance due to the phase of the breathing cycle.