Robust Longitudinal Ankle Edema Assessment Using Wearable Bioimpedance Spectroscopy

• Published in: IEEE transactions on biomedical engineering 2020-04, Vol.67 (4), p.1019-1029
• Main Authors: Mabrouk, Samer, Hersek, Sinan, Jeong, Hyeon Ki, Whittingslow, Daniel, Ganti, Venu G., Wolkoff, Paul, Inan, Omer T.
• Format: Article
• Language: English
• Subjects: Ankle; Cadavers; Calibration; Decision making; Edema; Electrical bioimpedance; Erbium; Error analysis; Hardware; Hidden Markov models; joint physiology; Measurement techniques; Nanoelectromechanical systems; Power consumption; Rehabilitation; Robustness; skin effect; Spectroscopy; Spectrum analysis; wearable sensing; Wearable technology
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2019.2927807

Objective: We present a robust methodology for tracking ankle edema longitudinally based on bioimpedance spectroscopy (BIS). Methods: We designed a miniaturized BIS measurement system and employed a novel calibration method that enables accurate, high-resolution measurements with substantially lower power consumption than conventional approaches. Using this state-of-the-art wearable BIS measurement system, we developed a differential measurement technique for robust assessment of ankle edema. This technique addresses many of the major challenges in longitudinal BIS-based edema assessment, including day-to-day variability in electrode placement, positional/postural variability, and intersubject variability. Results: We first evaluated the hardware in bench-top testing, and determined the error of the bioimpedance measurements to be 0.4 Ω for the real components and 0.54 Ω for the imaginary components with a resolution of 0.2 Ω. We then validated the hardware and differential measurement technique in: 1) an ex vivo, fresh-frozen, cadaveric limb model, and 2) a cohort of 11 human subjects for proof of concept (eight healthy controls and five subjects with recently acquired acute unilateral ankle injury). Conclusion: The hardware design, with novel calibration methodology, and differential measurement technique can potentially enable long-term quantification of ankle edema throughout the course of rehabilitation following acute ankle injuries. Significance: This could lead to better-informed decision making regarding readiness to return to activities and/or tailoring of rehabilitation activities to an individual's changing needs.