Heart failure (HF) is a complex syndrome in which the heart is unable to pump enough blood containing oxygen and nutrients to meet the body’s demands. HF is the leading cause of hospitalization for patients over 65 years of age. After a patient is diagnosed with HF, the mortality rate is 50% within the first 5 years. Presently, there is no unanimous diagnostic criteria for HF. Bioimpedance (BI) analysis has been proposed in recent years as a technique to detect one of the main symptoms: changes in body volume due to edema. This research presents a portable device (Volum), capable of performing real-time BI measurements in a low cost and non-invasive way. The goal is to improve patient monitoring at home to ensure rapid intervention in cases of worsening conditions, either with timely hospitalizations or adjustments to a patient’s usual treatment. Volum is a small, wearable, wireless, lightweight, low-power clinical pilot prototype, that takes measurements through four electrodes and sends the data via Bluetooth to an Android device.

A small, wearable, low-weight, and low-power-consumption device for plethysmography capacitive sensing is proposed herein. The device allows carrying out real-time monitoring of leg volume changes in patients suffering from heart failure (HF) conditions. The dynamic of fluid overload in patients with acute HF serves as a prognosis marker for this type of severe disease and, consequently, these patients can benefit from a wearable monitoring system to measure their body volume evolution during and after hospitalization. Our approach is based on contactless capacitive wearable structures implemented by two different sensor realizations located in the ankle: 180°-parallel capacitor plates (two modes of operations are compared, with the patient’s body connected to ground and to the average voltage between plates) and planar-parallel capacitor plates whose overlapped surface varies with the volume of the patient’s leg. Both realizations exhibit good sensitivity to leg volume changes. The acquisition of capacitance values is performed via a simple circuit that achieves notable performance in simulated volume analysis. A preliminary pilot clinical prototype is described as well.

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).

Congestive heart failure is a chronic disease that affects millions of people worldwide, characterized by the inability of the heart to pump enough blood with oxygen and nutrients, leading to fluid accumulation. Monitoring fluid accumulation is crucial in managing the disease, but current noninvasive methods have limitations in terms of size and connectivity. This study introduces Volum, a wearable device that measures calf bioimpedance to remotely monitor the progression of edema in patients with congestive heart failure. The device was first tested on a known RRC circuit, demonstrating high accuracy with a maximum error of 1%. It was also tested in 2 volunteers (1 patient and 1 control) for one month. The result showed consistent impedance values in the control throughout the month, while the patient showed high variability, in addition to a lower bioimpedance value. The results suggest the potential of the device for noninvasive monitoring of bioimpedance evolution. However, more research is needed to validate the measurements in a larger patient population and to explore the potential of the device for improving patient outcomes.

This paper explores the development of a low-cost alternating current (AC) smart current generator using ARM Cortex-M33 microcontrollers with integrated peripherals, Digital to Analog Converters (DAC) and Operational amplifiers (OPAMPS). The system generates an AC voltage signal through the DAC, which is then converted to an AC using integrated operational amplifiers and passive components. The proposed design provides a compact, low-power, cost-effective solution which is suitable for optimized embedded system sensor design. Results show a signal-to-noise ratio (SNR) of up to 70 dB and a total harmonic distortion (THD) as low as 0.2%, illustrating the potential for advanced sensing applications.

Heart-Failure (HF) is among the leading hospitalization causes in modern healthcare systems. In this paper, a method for performing continuous patient monitoring is presented with a focus on low power consumption. A prototype wearable device is being developed at the University of Sevilla to collect measurements. Among the sensing components there are two major blocks formed by a commercial biological impedance analog frontend from Analog Devices (AD5940) and an Inertial Motion Unit (IMU) capable of estimating attitude of the device. This information could provide a tremendous amount of information for the physician and help diagnose and remote monitor patients with HF. A major factor that can be analyzed to provide information on patient status is activity level and body states; time spent walking or standing, laying down or seated. In this work, a body tracking / activity estimation method is proposed for low power continuous monitoring. This study reports good results characterizing the laying down position and discriminating between laying down and standing/walking and seated. The presented results are relevant for clinical practice since body motion and position can serve as a health marker for patients. Additionally, the acquired motion information can be further processed to better understand artifacts and variations in the analog impedance measurements.