Wearable Vector Electrical Bioimpedance System to Assess Knee Joint Health

Abstract

Objective We designed and validated a portable electrical bioimpedance (EBI) system to quantify knee joint health. Methods Five separate experiments were performed to demonstrate the: (1) ability of the EBI system to assess knee injury and recovery; (2) inter-day variability of knee EBI measurements; (3) sensitivity of the system to small changes in interstitial fluid volume; (4) reducing the error of EBI measurements using acceleration signals; (5) use of the system with dry electrodes integrated to a wearable knee wrap. Results (1) The absolute difference in resistance (R) and reactance (X) from the left to the right knee was able to distinguish injured and healthy knees (p<0.05); the absolute difference in R decreased significantly (p<0.05) in injured subjects following rehabilitation. (2) The average inter-day variability (standard deviation) of the absolute difference in knee R was 2.5Ω, and for X was, 1.2 Ω. (3) Local heating/cooling resulted in a significant decrease/increase in knee R (p<0.01). (4) The proposed subject position detection algorithm achieved 97.4% leave-one subject out cross-validated accuracy and 98.2% precision in detecting when the subject is in the correct position to take measurements. (5) Linear regression between the knee R and X measured using the wet electrodes and the designed wearable knee wrap were highly correlated (r2 = 0.8 and 0.9, respectively). Conclusion This work demonstrates the use of wearable EBI measurements in monitoring knee joint health. Significance The proposed wearable system has the potential for assessing knee joint health outside the clinic/lab and help guide rehabilitation.

Fatigue-Induced Cole Electrical Impedance Model Changes of Biceps Tissue Bioimpedance

“…However, this will reduce the accuracy of collected measurements and needs to be investigated to determine the correct balance of measurement time/accuracy for these applications. Also, additional sensor data could be collected during bioimpedance measures to assess motion and posture to evaluate windows during which movement artifacts will not be impacting the bioimpedance data; with this approach having been implemented for wearable systems to assess knee joint health [33].…”

Fundamentals, Recent Advances, and Future Challenges in Bioimpedance Devices for Healthcare Applications

“…The injected current can be monitored to avoid exceeding the established limits [44], but the most common method is the injection of a fixed amplitude current [108]. Although multiple current source topologies have been employed for the VCSS, most are based on the improved Howland current pump [102,106], implemented by discrete designs based on operational amplifiers (OPAM).…”

“…Given their characteristics, bioimpedance measurements allow the characterization of biological media and organic tissues, including the human body, but also inorganic media [38]. In this sense, bioimpedance methods have been employed in skin monitoring (diagnosis of diseases and evaluation of a treatment progress) [38], cancerous tissue characterization and detection [31], sleep apnea detection through bioimpedance measurements [39], as a means of precisely controlling the energy delivered to the heart during defibrillation [40], as a predictor of intradialytic hypotension [41], for precise bone cement milling during revision of total hip replacement [42], for longitudinal knee joint health assessment [43,44], for the evaluation of high-resolution temporal information corresponding to pharyngeal swallowing [45], to monitor the ischemia and viability of transplanted organs [46,47], edema determination [48], brain and pulmonary function monitoring [49,50], and even as a method for the noninvasive measurement of glucose level [51].…”

Smart Bioimpedance Spectroscopy Device for Body Composition Estimation

“…This phase and frequency control is the basis of the calibration procedure described in Section 2.4. In addition, the proposed scheme allows the use of only a single multiplier to perform the demodulation of signals in phase and quadrature, which is the principle used for the measurement of the biompedance modulus and phase [1,37]. The measurement process is carried out in two stages: first, a frequency sweep in which the parameter Φ 5 takes the value 0 • is carried out for the evaluation of in-phase components; second, a subsequent frequency sweep with Φ 5 set to 90 • is performed to measure the quadrature-phase components.…”

“…is formed by the superposition of a sinusoidal waveform with frequently (2 · f 1 ) and a continuous level that depends on the phase lag between the input signals and their amplitudes. Thus, the continuous level of in-phase and quadrature components allow to calculate the bioimpedance modulus and phase by means of a coherent demodulation process [1,37]. This module is responsible for converting the analog signal (S 8 ) into digital signals with which the processing subsystem can operate.…”