RESUMEN
Chronic studies in the fasting and fed states of conscious subjects are fundamental for understanding the pathophysiological significance of functional gastrointestinal (GI) disorders and motility dysfunctions. To study the electrophysiology of the GI tract in the long term, the development of gastric implants is essential. This paper presents the development of an implantable system capable of monitoring the bioelectrical activity of the gastric system and modulating the activity in freely behaving rodents. The system consists of a miniature-sized implantable unit (IU), a stationary unit (SU) that communicates with the IU over a 2.4 GHz far-field radio frequency (RF) bidirectional link, and a charging unit (CU) that establishes an inductive 13.56 MHz near-field communication (NFC) with the IU, implementing an adaptive wireless power transfer (WPT). The CU can generate an adjustable power between +20 dBm and +30 dBm, and, in the presence of body movements and stomach motility, can deliver a constant rectified voltage to the IU. The live subject's exposure to the electromagnetic WPT in the developed system complies with the RF energy absorption restrictions for health and safety concerns. The system can be utilized to investigate the relationship between functional GI disorders and dysrhythmias in the gastric bioelectrical activity and study the potential of electroceutical therapies for motility dysfunctions in clinical settings.
RESUMEN
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.