The Sensitivity of Bioimpedance to Assess Leg Fluid Volume Changes in Children on Hemodialysis: Experimental...

Fluid management plays an essential role in pediatric hemodialysis; however, traditional assessment techniques often lack the precision required for this patient population. Bioimpedance analysis (BIA) offers a non-invasive alternative, but electrode placement significantly impacts measurement sensitivity. This study compared the efficacy of two calf-based electrode configurations - dorsal (ankle) versus plantar (sole) - in detecting fluid volume changes via bioimpedance in pediatric patients, particularly in terms of their sensitivity. Additionally, we evaluated a novel ring electrode arrangement for optimizing sensitivity distribution in lower limb tissues.

This controlled before-and-after study was conducted at the dialysis unit of Ali Asghar Children's hospital in Tehran, Iran. It evaluated thirteen children (aged 3-15 years) undergoing hemodialysis using bioimpedance analysis. The primary outcome measure was the change in impedance values before and after a single dialysis session. Measurements were performed with electrodes placed in two configurations: between the plantar surface of the foot to below the knee (down), and between the ankle dorsal surface to below the knee (up). Current distribution patterns were modeled using COMSOL simulations.

Mean ultrafiltration volume was 1123 ± 384 mL per session. Impedance changes were observed in both dorsal and plantar electrode configurations, with no significant differences or superiority in measuring these changes. Sensitivity analysis revealed variations of 35% with dorsal placement, 24% with plantar placement, and 20% with ring electrode configuration, demonstrating superior uniformity of the ring design across tissue regions.

Optimal electrode placement varies among patients with no universal advantage for either position. Bioimpedance sensitivity depends on location of fluid accumulation, and enhanced sensitivity is required for monitoring changes below two liters. The ring electrodes provided the most uniform sensitivity distribution. These findings support use of personalized bioimpedance monitoring approaches to improve fluid management precision in pediatric hemodialysis.