A Wearable Wideband Analog Bio-Impedance Analyzer for Real-Time Monitoring of Human Physiology

Continuous monitoring of electrophysiological activities of the human body is a significant step toward the effective prognosis, diagnosis, and management of functional disorders and cardiovascular diseases. This paper presents the development of a wireless system for the real-time acquisition of hemodynamics data and ambulatory monitoring of body composition based on electrical bio-impedance (Bio-Z) analysis. The developed system is composed of a low-power wearable unit and a stationary unit connected to a computer. The system conducts the non-radiative non-invasive Bio-Z analysis over a wide bandwidth of 1 MHz through four independent channels. The proposed analog approach detects the physiological activity by extracting the magnitude of the mixed Bio-Z signal, in real-time. A graphical user interface was designed for monitoring, analysis, and storage of the processed data. Moreover, the amplitude and frequency of the electrical excitation signals can be instructed through the user interface, wirelessly. Bench-top validation of the system demonstrated the delivery of current signals over a wide frequency range of 1 kHz - 1 MHz and peak-to-peak amplitude of up to 20 mA. Besides, the system was able to detect the magnitude of the envelope of the mixed signal with amplitude modulation depths as low as 0.1 %. Clinical Relevance- The system provides the real-time monitoring of cardiac activity and blood pulsation in human arteries. In addition, due to the configurability of the frequency and amplitude of the current injection circuit, the system is an excellent candidate to be utilized for real-time medical imaging through electrical bio-impedance tomography as well as electrical bio-impedance spectroscopy.