A Practical Method to Reduce Electrode Mismatch Artefacts during 4-electrode BioImpedance Spectroscopy Measurements

We present a novel and practical method of removing distortions due to electrode impedance mismatch encountered during 4-electrode bioimpedance spectroscopy (BIS) measurements. Recorded localised, or even whole-body, tissue impedances often evidence high frequency artefacts which resemble additional capacitive or inductive behaviours. We show that making two impedance measurements with the same four electrodes, but by connecting them in different arrangements, we can cause either the observed high-frequency capacitive behaviour or the inductive behaviour. Additionally, simply calculating the mean of these two distorted data sets leads to a corrected, "artefact-free" impedance close to that expected. This correction method was validated on R-C networks (simulated as well as measured) and on biological tissue measurements ( healthy forearm and oedematous leg). The described method was found valid using an SFB7 Impedimed (R) over a frequency range of 3 to 1000 kHz. It is possible that other impedance meters and frequency ranges could also benefit from this simple technique.