Validating Continuous Ankle Bioimpedance as a Biomarker for Fluid Status in Acute Congestive Heart Failure

Acute decompensated heart failure (ADHF) is one of the leading causes for hospitalization in the US. Patient’s weight and limb girth are monitored to assess medication efficacy and readiness for hospital discharge. Such metrics are assessed manually by a trained professional at discrete time intervals, thereby missing potentially critical information about treatment responsiveness. Full, upper, and lower-body bioimpedance analysis have shown promise in tracking changes in patient weight, but requires bulky systems to place electrodes across different limbs. In this work, we evaluate the use of convenient ankle limb bioimpedance for tracking fluid status changes in a proof-of-concept dataset obtained in 9 hospitalized patients with ADHF. Continuous bioimpedance measurements were recorded while the patients received diuretic treatment for more than 2 days. Biomarkers derived from the low-frequency bioimpedance measurements, ratio of low-to-high bioimpedance measurements and limb girth were significantly different from hospital admission to discharge. Bioimpedance measures correlated to changes in weight (Pearson’s r = − 0.63, subject-specific), and limb girth (Pearson’s r = − 0.83 and r = − 0.87, subject-specific and global, respectively). Such bioimpedance measures captured from the ankle in a wearable form-factor and in a continuous manner provide better insight to the patient’s acute response to medication. Such a tool can be further used to better schedule medications and alter dosage in the clinic and be sent home with patients to detect fluid accumulation early.