Bioimpedanciómetro basado en microcontrolador de 32 bits

En este trabajo se presenta el desarrollo de un bioimpedanciómetro basado en un diseño propio, de implementación simple, tamaño reducido y bajo costo basado en un microcontrolador de 32 bits de arquitectura ARM. Se describe el sistema por completo y se muestran registros de medidas en diversas situaciones. Se presenta también el desarrollo de una aplicación en PC que permite visualizar en tiempo real distintas variables de interés en la medida de bioimpedancia. La validación del sistema implementado constituye un punto de partida sólido para el desarrollo de una segunda versión vestible y con enlace inalámbrico.This work presents the development of a proprietary bioimpedance meter based on an own design, simple to implement, small in size and low cost, based on a 32-bit microcontroller with ARM architecture. The entire system is described, and measurement logs are shown in various situations. The development of a PC application that allows real-time visualization of different variables of interest in bioimpedance measurement is also presented. The validation of the implemented system constitutes a solid starting point for the development of a second version embedded in a wearable system with a wireless link.Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señale

Time Stamp – A Novel Time-to-Digital Demodulation Method for Bioimpedance Implant Applications

Bioimpedance analysis is a noninvasive and inexpensive technology used to investigate the electrical properties of biological tissues. The analysis requires demodulation to extract the real and imaginary parts of the impedance. Conventional systems use complex architectures such as I-Q demodulation. In this paper, a very simple alternative time-to-digital demodulation method or ‘time stamp’ is proposed. It employs only three comparators to identify or stamp in the time domain, the crossing points of the excitation signal, and the measured signal. In a CMOS proof of concept design, the accuracy of impedance magnitude and phase is 97.06% and 98.81% respectively over a bandwidth of 10 kHz to 500 kHz. The effect of fractional-N synthesis is analysed for the counter-based zero crossing phase detector obtaining a finer phase resolution (0.51˚ at 500 kHz) using a counter clock frequency ( fclk = 12.5 MHz). Because of its circuit simplicity and ease of transmitting the time stamps, the method is very suited to implantable devices requiring low area and power consumption

A Feedback-Based Pneumatic Compression System for Effective Lymphedema Management

Bioimpedance analysis (BIA) is a method of detecting lymphedema- a debilitating medical condition involving swelling of the extremities. Pneumatic compression devices are frequently used in the compression treatment of lymphedema. Although existing compression technology provides relief of symptoms, it has limitations in terms of ease-of-use, portability, and monitoring of treatment progress. Currently, there are no BIA analyzers in the market that run on a low-power microcontroller and a rechargeable battery. Moreover, no such device currently exists that integrate the BIA analysis with pneumatic compression system to offer a feedback-based solution for lymphedema treatment. This work represents the first steps towards a complete system and describes the pneumatic compression and circuit designs for a portable BIA analyzer. The study proposes a lightweight, battery operated pneumatic compression device that can apply a pressure of 50 mmHg in a four-chamber compression garment. A microcontroller-based BIA system that can provide accurate indication of swelling based on a Nyquist plot was introduced. The envisioned mechatronic system features programmable compression sequences and operates with the human-in-the-loop using bioimpedance spectroscopy as control feedback. Performance of the compression system is verified by measurement of applied pressures and the BIA circuits are validated for single frequency and multi frequency impedance analysis of a phantom test load. With further development in the future, the system has the potential to serve as a quantitative source of valuable diagnostic information for clinicians, and in the long run may enable the smart management of lymphedema with the device essentially prescribing the course of treatment in response to measured conditions. This kind of human-in-the-loop control system may be a breakthrough in treatment of chronic conditions

Mobile core hydration sensing using bio-impedance of arm

A novel arm-wearable mobile core hydration sensor has been designed which works on the principle of Bio-Impedance Vector Analysis (BIVA). Arm impedance is hypothesized to be indicative of core hydration changes. The prototype device is a Flexible PCB that uses gel electrodes for tetrapolar measurement of the arm impedance and uses Bluetooth transmission to transmit the raw data to a base station for data processing, where the resistance and reactance at 50kHz are extracted. The device transmits raw data every 2 seconds, with 2mA average current consumption and measurement error of less than 1% and is ensured to be safe for a wearer by meeting IEC6060-1 safety standards. Device design, evolution, manufacturing, calibration, and validation are discussed in detail. The arm-impedance is analyzed with respect to different arm angles, muscle strain and electrode placement sites, and a Posture control protocol is incorporated to deal with such impacts. Experimental protocols for testing hydration status are explained and the results of a pilot study are presented and analyzed. Physiological signal responses, like Body weight, Heart Rate, and Core temperature, are monitored in the experiment trials, and are used to interpret the results of the hydration study. The pilot study results look promising, and can distinguish between dehydration and euhydration, with arm impedance showing better demarcations than body impedance. Moving forward, this research will be validated by experimentation on multiple subjects.Electrical and Computer Engineerin