Multimodal Electrophysiology via Ingestible, Gastric, Untethered Tracking of Organ-Level Bioelectric Activity

Introduction:: Despite growing interest in the gut-brain axis, gastrointestinal electrophysiology in large mammals remains understudied due to the invasiveness of placing high-fidelity systems without limiting subject movements. Electrodes must either be implanted surgically, or worn on the skin resulting in a tradeoff between signal quality and invasiveness. Here we introduce a system for multimodal electrophysiology via ingestible, gastric, untethered tracking (MiGUT) which can record electrical signals in the stomach. MiGUT can record distinct signals including the slow wave and other gastric electrical activity in the stomach, as well as the heart and respiration signals due to its proximity to associated vital organs. Moreover, MiGUT can monitor slow wave activity in freely moving and feeding animals, demonstrating a new concept for ingestible electronics and the study of gastric electrophysiology.


Materials and Methods:: The MiGUT system consists of an electronics module and flexible measurement electrodes. The electronics are housed in a 3D printed case which was designed to be comparable to FDA cleared products such as capsule endoscopy systems (Medtronic PillCam, ⌀11x26mm) to facilitate future clinical translation. Biopotentials are measured using an eight channel 16-bit analog-to-digital converter (ADC) and are wirelessly transmitted to a base station using a microcontroller with integrated 915 MHz transceiver. The current consumption of the device depends on the sampling frequency, providing flexibility in balancing experiment length and signal fidelity. Duty cycling between measurement mode and low power sleep mode enables experiments to be conducted over a number of days. With a panel antenna approximately one to four meters away from the device in a freely moving swine, an external 915 MHz transceiver was found to reliably receive over 99% of data from the MiGUT system at approximately -70dBm in a full stomach and during multiple behaviors. A flat flexible cable connector on the electronics module enables a range of flexible electrode designs that can be used with the system, such as custom designed electrodes fabricated using flexible printed circuit board (PCB) manufacturing methods. Using this system we measure the gastric electrical activity in anesthetized and freely moving large animals (swine), and wirelessly collect baseline electrical activities as well as measurements during feeding and introduction of motility agents.

Results, Conclusions, and Discussions:: Our ingestible MiGUT system is capable of recording high quality electrical signals from the gastric environment, including gastric slow wave, heart rate, respiration rate, as well as long period waves which may be associated with processes related to the migrating myoelectric complex. This is exciting as the MiGUT device demonstrates a concept for monitoring of vital organ monitoring without requiring devices worn/implanted on the skin surface, which could be detached during subject activity. Moreover, we are able to distinguish medication-induced motility changes and measure high quality mucosal gastric slow waves during animal feeding and ambulation absent any tethering or wearable system, a capability which has not been reported to date. These promising results show the potential for long term study of gastric electrophysiology, and a strategy to obtain high quality recordings without restriction to subject movement, meals or day-to-day life.


Acknowledgements (Optional): :

References (Optional): :