A novel scalable electrode array and system for non‐invasively assessing gastric function using flexible electronics

Abstract

Background: Disorders of gastric function are highly prevalent, but diagnosis often remains symptom-based and inconclusive. Body surface gastric mapping is an emerging diagnostic solution, but current approaches lack scalability and are cumbersome and clinically impractical. We present a novel scalable system for non-invasively mapping gastric electrophysiology in high-resolution (HR) at the body surface. Methods:The system comprises a custom-designed stretchable high-resolution "peel-and-stick" sensor array (8 × 8 pre-gelled Ag/AgCl electrodes at 2 cm spacing; area 225 cm 2 ), wearable data logger with custom electronics incorporating bioamplifier chips, accelerometer and Bluetooth synchronized in real-time to an App with cloud connectivity. Automated algorithms filter and extract HR biomarkers including propagation (phase) mapping. The system was tested in a cohort of 24 healthy subjects to define reliability and characterize features of normal gastric activity (30 m fasting, standardized meal, and 4 h postprandial).Key Results: Gastric mapping was successfully achieved non-invasively in all cases (16 male; 8 female; aged 20-73 years; BMI 24.2 ± 3.5). In all subjects, gastric electrophysiology and meal responses were successfully captured and quantified non-invasively (mean frequency 2.9 ± 0.3 cycles per minute; peak amplitude at mean 60 m postprandially with return to baseline in <4 h). Spatiotemporal mapping showed regular and consistent wave activity of mean direction 182.7° ± 73 (74.7% antegrade, 7.8% retrograde, 17.5% indeterminate). Conclusions and Inferences:BSGM is a new diagnostic tool for assessing gastric function that is scalable and ready for clinical applications, offering several biomarkers that are improved or new to gastroenterology practice.

Normative values for body surface gastric mapping evaluations of gastric motility using Gastric Alimetry: spectral analysis

“…39 Previous work has also demonstrated that an amplitude increase in response to a meal is a normal feature of cutaneous gastric recordings, with ff-AR metrics previously commonly employed in EGG studies, albeit over substantially shorter time periods. 10,[20][21][22] However, we noticed that many healthy controls demonstrate high fasting baseline amplitude at the gastric frequency, such that the perceived meal response is diminished or absent. This finding could be due to cephalic-phase gastric activity, 40 migrating motor complex activity, 41 or circadian variations.…”

“…8 BSGM employs a dense grid of electrodes to non-invasively map gastric activity in high-resolution at the epigastrium, registering the myoelectrical activity that coordinates gastric motility and peristaltic activity through an increase in signal strength. 9,10 BSGM represents a critical advance over traditional electrogastrography (EGG) approaches due to a combination of technical improvements that serve to maximally extract the weak underlying gastric signals while minimizing contamination by noise. These features include a high-resolution (HR) array of large area that accounts for gastric anatomical biodiversity while allowing signal summation from multiple sites, bioelectronics and signal processing systems specifically optimized for gastric electrophysiology, and a robust validated artifact detection and rejection scheme.…”

“…9,11,13 The first commercial medical device for performing BSGM has recently become available, with United States Food and Drug Administration clearance (Gastric Alimetry®, Alimetry, New Zealand), enabling clinical use with the goal of reducing diagnostic uncertainty. 10,11,14 Standardised clinical application of a diagnostic medical physiology device requires a thorough understanding of normative metric intervals. For BSGM, two categories of metrics are recognized: i) spectral metrics encompassing myoelectrical frequency, amplitude, rhythm stability, and meal responses; and ii) spatial metrics characterising wave propagation dynamics.…”

“…[9][10][11] Spectral metrics are derived from a spectral plot, and represent a form of HR-EGG, achieving robust improvements over traditional EGG metrics. 8,10,12,15 Spectral metrics are currently the most established form of analytics, with a recent BSGM study principally employing these to identify a distinct subgroup of patients with gastric neuromuscular abnormalities in nausea and vomiting syndromes. 11 The aim of this study was to establish normative reference intervals for spectral BSGM metrics for Gastric Alimetry, encompassing the Principal Gastric Frequency, Gastric Alimetry Rhythm Index (GA-RI), BMI-adjusted amplitude, and the fed:fasted amplitude ratio.…”

“…9,11,13 The first commercial medical device for performing BSGM has recently become available, with United States Food and Drug Administration clearance (Gastric Alimetry®, Alimetry, New Zealand), enabling clinical use with the goal of reducing diagnostic uncertainty. 10,11,14…”