A novel wearable bioimpedance sensor for continuous monitoring of fluid balance: a study on isotonic hypovolemia in healthy adults.

Purpose: This study aimed to investigate the ability of a novel wearable bioimpedance sensor to monitor changes in fluid balance induced by furosemide. Because iso-osmotic fluid loss is expected to primarily comprise fluid from the extracellular compartment it was hypothesized that isotonic hypovolemia would increase the extracellular resistance (R_E).

Methods: 27 healthy adults (20 women, 7 men; 35 ± 10 year.) were continuously monitored by the bioimpedance sensor following administration of furosemide. Body weight, blood pressure, heart rate, sensation of thirst and selected blood parameters were tested before furosemide administration (t0), one hour (t1) and two hours (t2) after furosemide administration, and one hour after intake of a sports drink containing carbohydrate and electrolytes (t3). Urine elimination was measured throughout the intervention, and the change in extracellular fluid volume was estimated using urine elimination and established equations.

Results: During hypovolemia body weight was reduced by 1.4 ± 0.2 kg (1.7 ± 0.4%). Total urine elimination during fluid loss was 1277 ± 190 mL. R_E increased significantly from t0 to t2 (13.6 ± 2.9%). A strong correlation was observed between the estimated change in extracellular fluid volume and the measured change in R_E during the isotonic fluid loss.

Conclusion: This study demonstrates that the wearable bioimpedance device tested is very sensitive to furosemide-induced changes in fluid volume in healthy volunteers in a controlled environment. Additional research is needed to evaluate the ability of the device to track fluid status in a clinical setting.

Trial registration: The study was registered at clinicaltrials.gov 29th of October 2021 (NCT05129358).