In vivo experimental validation of detection of gastric slow waves using a flexible multichannel electrogastrography sensor linear array.

BACKGROUND: Cutaneous electrogastrography (EGG) is a non-invasive technique that detects gastric bioelectrical slow waves, which in part govern the motility of the stomach. Changes in gastric slow waves have been associated with a number of functional gastric disorders, but to date accurate detection from the body-surface has been limited due to the low signal-to-noise ratio. The main aim of this study was to develop a flexible active-electrode EGG array. METHODS: Two Texas Instruments CMOS operational amplifiers: OPA2325 and TLC272BID, were benchtop tested and embedded in a flexible linear array of EGG electrodes, which contained four recording electrodes at 20-mm intervals. The cutaneous EGG arrays were validated in ten weaner pigs using simultaneous body-surface and serosal recordings, using the Cyton biosensing board and ActiveTwo acquisition systems. The serosal recordings were taken using a passive electrode array via surgical access to the stomach. Signals were filtered and compared in terms of frequency, amplitude, and phase-shift based on the classification of propagation direction from the serosal recordings. RESULTS: The data were compared over 709 cycles of slow waves, with both active cutaneous EGG arrays demonstrating comparable performance. There was an agreement between frequencies of the cutaneous EGG and serosal recordings (3.01 ± 0.03 vs 3.03 ± 0.05 cycles per minute; p = 0.75). The cutaneous EGG also demonstrated a reduction in amplitude during abnormal propagation of gastric slow waves (310 ± 50 µV vs 277 ± 9 µV; p < 0.01), while no change in phase-shift was observed (1.28 ± 0.09 s vs 1.40 ± 0.10 s; p = 0.36). CONCLUSION: A sparse linear cutaneous EGG array was capable of reliably detecting abnormalities of gastric slow waves. For more accurate characterization of gastric slow waves, a two-dimensional body-surface array will be required.

The effects of low-and high-frequency non-invasive transcutaneous auricular vagal nerve stimulation (taVNS) on gastric slow waves evaluated using in vivo high-resolution mapping in porcine.

BACKGROUNDS: Gastric motility is regulated by an electrophysiological activity called slow-wave and neuronal innervations by the vagus nerve. Transcutaneous auricular vagal nerve stimulation (taVNS) has been demonstrated to have therapeutic potential for a wide range of medical conditions, including the management of gastric dysfunctions. The main objective of this study was to gain a better understanding of how non-invasive neuromodulation influences gastric slow wave under in vivo conditions. METHODS: TaVNS protocols were applied in conjunction with 192-channel gastric bioelectrical mapping in porcine subjects under general anesthesia. The spatiotemporal profiles of gastric slow wave were assessed under two different taVNS protocols at 10 and 80 Hz. KEY RESULTS: The taVNS protocols effectively altered the interval and amplitude of gastric slow waves, but not the velocity or the percentage of spatial dysrhythmias. In the subjects that responded to the protocols, the 10 Hz protocol was shown to normalize slow-wave propagation pattern in 90% of the subjects, whereas the 80 Hz protocol was shown to inhibit slow waves in 60% of the subjects. CONCLUSIONS AND INFERENCES: Chronic responses of gastric motility and slow waves in response to taVNS should be investigated using non-invasive means in conscious subjects in future.