Measuring fluid balance in end-stage renal disease with a wearable bioimpedance sensor

Background: Accurate assessment of fluid volume and hydration status is essential in many disease states, including patients with chronic kidney disease. The aim of this study was to investigate the ability of a wearable continuous bioimpedance sensor to detect changes in fluid volume in patients undergoing regular hemodialysis (HD).

Methods: 31 patients with end-stage renal disease were enrolled and monitored with a sensor patch (Re:Balans^®) on the upper back through two consecutive HD sessions and the interdialytic period between. The extracellular resistance R_E was calculated from multi-frequency bioimpedance measurements and was hypothesized to correlate with the amount of extracted fluid during dialysis.

Results: Only HD sessions with a positive net fluid extraction were included in the primary analysis. Participants had an increase of 7.5 ± 4.3 Ω (Ohm) in R_E during the first HD and 6.2 ± 2.3 Ω during the second HD, and a fluid extraction (ultrafiltration (UF) volume) of 1.5 ± 0.8 L and 1.2 ± 0.6 L, respectively. The relative change in R_E during HD correlated strongly with UF volume (r = 0.82, p < 0.001). During the interdialytic period, the patients had a mean decrease in R_E of 6.0 ± 3.5 Ω. Longitudinal changes in R_E (%) and body weight (kg) over the entire study period was negatively correlated (r = -0.61 p < 0.001). Longitudinal changes in blood samples and cardiovascular changes were also in agreement with changes in weight and R_E.

Conclusions: The results of this clinical investigation indicate that the investigational device is capable of tracking both rapid and gradual changes in hydration status in patients undergoing regular HD.