Characterization and Correction of Low Frequency Artifacts in Segmental Bioimpedance Measurements

Bioimpedance analysis can be used for remote monitoring of volume status for various conditions such as congestive heart failure. The measurement is typically performed with four electrodes, two of them driving an alternating current through the tissue and the other two sensing the resulting voltage. Issues with the measurement setup such as stray capacitance or electrode mismatch can cause artifacts that impact Cole parameters used for volume estimation. While previous research has focused on mitigating high frequency artifacts, little research has been done to understand the cause and impact of low frequency artifacts, nor how to mitigate the impact of these artifacts. These artifacts are most prevalent in wearable segmental bioimpedance systems, especially using textile electrodes, so future research in this area is needed for these systems to be viable. The present study uses simulations to identify the potential sources of low frequency artifacts, and explores techniques to minimize the impact of these artifacts on Cole parameters. Theoretical analysis and simulations show that the mismatch of the voltage electrodes causes artifacts at low frequency. These artifacts are highly dependent on the impedance of the negative current injecting electrode. Averaging measurements of the mismatch of both voltage electrodes and limiting high frequency measurements to 200 kHz can reduce errors due to these artifacts from over 137% to less than 3%. The results of this study suggest the impact of low frequency artifacts can be significantly reduced, enabling future development of wearable bioimpedance systems.Clinical relevance— Reducing the impact of low frequency artifacts on Cole parameter estimation enables wearable segmental bioimpedance systems that can be used for remote monitoring of volume status in home environments.