Wearable Devices Based on Bioimpedance Test in Heart-Failure: Design Issues.

Heart-failure (HF) is a severe medical condition. Physicians need new tools to monitor the health status of their HF patients outside the hospital or medical supervision areas, to better know the evolution of their patients' main biomarker values, necessary to evaluate their health status. Bioimpedance (BI) represents a good technology for sensing physiological variables and processes on the human body. BI is a non-expensive and non-invasive technique for sensing a wide variety of physiological parameters, easy to be implemented on biomedical portable systems, also called "wearable devices". In this systematic review, we address the most important specifications of wearable devices based on BI used in HF real-time monitoring and how they must be designed and implemented from a practical and medical point of view. The following areas will be analyzed: the main applications of BI in heart failure, the sensing technique and impedance specifications to be met, the electrode selection, portability of wearable devices: size and weight (and comfort), the communication requests and the power consumption (autonomy). The different approaches followed by biomedical engineering and clinical teams at bibliography will be described and summarized in the paper, together with results derived from the projects and the main challenges found today.

Wearable Devices Based on Bioimpedance Test in Heart Failure: Clinical Relevance: Systematic Review.

Background: Heart failure (HF) represents a frequent cause of hospital admission, with fluid overload directly contributing to decompensations. Bioimpedance (BI), a physical parameter linked to tissue hydration status, holds promise in monitoring congestion and improving prognosis. This systematic review aimed to assess the clinical relevance of BI-based wearable devices for HF fluid monitoring. Methods: A systematic review of the published literature was conducted in five medical databases (PubMed, Scopus, Cochrane, Web of Science, and Embase) for studies assessing wearable BI-measuring devices on HF patients following PRISMA recommendations on February 4th, 2024. The risk of bias was evaluated using the ROBINS tool. Results: The review included 10 articles with 535 participants (mean age 66.7 ± 8.9 years, males 70.4%). Three articles identified significant BI value differences between HF patients and controls or congestive vs non-congestive HF patients. Four articles focused on the devices' ability to predict HF worsening-related events, revealing an overall sensitivity of 70.0 (95% CI 68.8-71.1) and specificity of 89.1 (95% CI 88.3-89.9). One article assessed prognosis, showing that R80kHz decrease was related to all-cause-mortality with a hazard ratio (HR) of 5.51 (95% CI 1.55-23.32; p = 0.02) and the composite all-cause-mortality and HF admission with a HR of 4.96 (95% CI 1.82-14.37; p = 0.01). Conclusions: BI-measuring wearable devices exhibit efficacy in detecting fluid overload and hold promise for HF monitoring. However, further studies and technological improvements are required to optimize their impact on prognosis compared to standard care before they can be routinely implemented in clinical practice. PROSPERO Registration: The search protocol was registered at PROSPERO (CRD42024509914).

Characterization and Correction of Low Frequency Artifacts in Segmental Bioimpedance Measurements.

Bioimpedance analysis can be used for remote monitoring of volume status for various conditions such as congestive heart failure. The measurement is typically performed with four electrodes, two of them driving an alternating current through the tissue and the other two sensing the resulting voltage. Issues with the measurement setup such as stray capacitance or electrode mismatch can cause artifacts that impact Cole parameters used for volume estimation. While previous research has focused on mitigating high frequency artifacts, little research has been done to understand the cause and impact of low frequency artifacts, nor how to mitigate the impact of these artifacts. These artifacts are most prevalent in wearable segmental bioimpedance systems, especially using textile electrodes, so future research in this area is needed for these systems to be viable. The present study uses simulations to identify the potential sources of low frequency artifacts, and explores techniques to minimize the impact of these artifacts on Cole parameters. Theoretical analysis and simulations show that the mismatch of the voltage electrodes causes artifacts at low frequency. These artifacts are highly dependent on the impedance of the negative current injecting electrode. Averaging measurements of the mismatch of both voltage electrodes and limiting high frequency measurements to 200 kHz can reduce errors due to these artifacts from over 137% to less than 3%. The results of this study suggest the impact of low frequency artifacts can be significantly reduced, enabling future development of wearable bioimpedance systems.Clinical relevance- Reducing the impact of low frequency artifacts on Cole parameter estimation enables wearable segmental bioimpedance systems that can be used for remote monitoring of volume status in home environments.

DC electrical stimulation enhances proliferation and differentiation on N2a and MC3T3 cell lines.

BACKGROUND: Electrical stimulation is a novel tool to promote the differentiation and proliferation of precursor cells. In this work we have studied the effects of direct current (DC) electrical stimulation on neuroblastoma (N2a) and osteoblast (MC3T3) cell lines as a model for nervous and bone tissue regeneration, respectively. We have developed the electronics and encapsulation of a proposed stimulation system and designed a setup and protocol to stimulate cell cultures. METHODS: Cell cultures were subjected to several assays to assess the effects of electrical stimulation on them. N2a cells were analyzed using microscope images and an inmunofluorescence assay, differentiated cells were counted and neurites were measured. MC3T3 cells were subjected to an AlamarBlue assay for viability, ALP activity was measured, and a real time PCR was carried out. RESULTS: Our results show that electrically stimulated cells had more tendency to differentiate in both cell lines when compared to non-stimulated cultures, paired with a promotion of neurite growth and polarization in N2a cells and an increase in proliferation in MC3T3 cell line. CONCLUSIONS: These results prove the effectiveness of electrical stimulation as a tool for tissue engineering and regenerative medicine, both for neural and bone injuries. Bone progenitor cells submitted to electrical stimulation have a higher tendency to differentiate and proliferate, filling the gaps present in injuries. On the other hand, neuronal progenitor cells differentiate, and their neurites can be polarized to follow the electric field applied.