Band Electrodes Reduce Simulated Calf Bioimpedance Measurement Errors Due to Muscle Anisotropy

Remote monitoring of fluid status via calf bioimpedance measurements could improve the experience of patients with congestive heart failure and reduce readmission rates. Most measurements today use conventional Ag/AgCl electrodes and a short inter-electrode spacing, resulting in current flowing primarily near the electrodes, preventing deeper current penetration and in turn accurate volume estimation. Textile band electrodes may more evenly distribute current throughout the calf. In the present study, simulations were conducted to investigate the impact of inter-electrode spacing/placement and fat tissue on bioimpedance using both Ag/AgCl electrodes and textile band electrodes. Simulation results showed that increasing the inter-electrode spacing can improve current distribution in the tissue, but there are still errors that increase with fat thickness (14.3% error at 10 cm spacing down to 1.7% error at 20 cm spacing for a "nominal" fat thickness, vs. -0.3% and -0.5% error for band electrodes). Band electrodes most closely matched the expected resistance and seem the most suitable regardless of inter-electrode spacing.