Sa1974 Characterizing Gastrointestinal (GI) Motility With a Computer-Aided, Non-Invasive Acoustic Sensor: Proof-of-Concept Testing in Normal Controls vs. Postoperative Patients

Abstract

Background: motility disorders are highly prevalent and expensive. Motility testing is limited to invasive modalities, such as antroduodenal manometry or SmartPill, that provide one-time results not longitudinal tracking of dynamic physiology. Previous work showed that continuous audio recordings of bowel sounds from the abdominal wall correlates with manometry (Tomomasa AJG 1999). But until recently, there was no way to perform acoustic monitoring in a clinically feasible, cost-effective, point-of-care manner. Using advances in low-cost sensor technologies and computer-aided analysis, we developed a disposable, noninvasive Acoustic Surveillance (AGIS) sensor. We performed a proof-of-concept study to test whether monitoring can distinguish healthy controls (HC) from patients (Pts) recovering from colorectal surgery tolerating oral intake vs. those with postoperative ileus (POI): a model dysmotility syndrome suitable for initial testing. Methods: The device is a disposable plastic sensor embedded with a high-fidelity microphone that adheres to the abdominal wall (Figure). The device connects to a bedside gateway box that measures motility events with a signal-search engine. The results are displayed as GI telemetry and the computer calculates an AGIS index, defined as acoustic events scaled per second. We recruited HC subjects to wear the device for 2 hours following a breakfast of two eggs, a slice of bread, and a beverage. We compared their index to similar recordings of Pts recovering from colorectal surgery at a University-based VA medical center. We divided Pts into those tolerating postop feeding (Pts-Feed) vs. those with POI (Pts-POI) marked by nausea, vomiting, nasogastric lavage or failure to advance beyond sips. We used ANOVA to compare indices among groups and t-tests between groups. Results: There were 6 HC (mean age=28.5+3.1; 50%M), 7 Pts-Feed (age=65.4+4.6; 100%M) and 25 Pts-POI (age=63.4+10.7; 100%M). The mean+SD indices were 0.14+0.02, 0.03+0.0, and 0.016+0.01 events/second for HC, Pts-Feed and Pts-POI, respectively (ANOVA p<0.001). Using a diagnostic threshold of 0.1/second, the index was 97% sensitive and 85% specific for separating Pts from HC. When placed on a relative scale, the Pts-Feed and PtsPOI mean indices were only 26% and 11% that of HCs. Among postop Pts, there was a higher index in Pts-Feed vs Pts-POI (p=0.017). Conclusion: In this proof-ofconcept study, non-invasive monitoring of abdominal acoustics using a low-cost, disposable