An experimental method to identify neurogenic and myogenic active mechanical states of intestinal motility

Excitatory and inhibitory enteric neural input to intestinal muscle acting on ongoing myogenic activity determines the rich repertoire of motor patterns involved in digestive function. The enteric neural activity cannot yet be established during movement of intact intestine in vivo or in vitro. We propose the hypothesis that is possible to deduce indirectly, but reliably, the state of activation of the enteric neural input to the muscle from measurements of the mechanical state of the intestinal muscle. The fundamental biomechanical model on which our hypothesis is based is the “three-element model” proposed by Hill. Our strategy is based on simultaneous video recording of changes in diameters and intraluminal pressure with a fiber-optic manometry in isolated segments of rabbit colon. We created a composite spatiotemporal map (DPMap) from diameter (DMap) and pressure changes (PMaps). In this composite map rhythmic myogenic motor patterns can readily be distinguished from the distension induced neural peristaltic contractions. Plotting the diameter changes against corresponding pressure changes at each location of the segment, generates “orbits” that represent the state of the muscle according to its ability to contract or relax actively or undergoing passive changes. With a software developed in MatLab, we identified twelve possible discrete mechanical states and plotted them showing where the intestine actively contracted and relaxed isometrically, auxotonically or isotonically, as well as where passive changes occurred or was quiescent. Clustering all discrete active contractions and relaxations states generated for the first time a spatio-temporal map of where enteric excitatory and inhibitory neural input to the muscle occurs during physiological movements. Recording internal diameter by an impedance probe proved equivalent to measuring external diameter, making possible to further develop similar strategy in vivo and humans.Australian National Health and Medical Research Counci

Predicting the Activation States of the Muscles Governing Upper Esophageal Sphincter Relaxation and Opening

Copyright © 2016 the American Physiological SocietyThe swallowing muscles that influence upper esophageal sphincter (UES) opening are centrally controlled and modulated by sensory information. Activation and deactivation of neural inputs to these muscles, including the intrinsic cricopharyngeus (CP) and extrinsic submental (SM) muscles, results in their mechanical activation or deactivation, which changes the diameter of the lumen, alters the intraluminal pressure, and ultimately reduces or promotes flow of content. By measuring the changes in diameter, using intraluminal impedance, and the concurrent changes in intraluminal pressure, it is possible to determine when the muscles are passively or actively relaxing or contracting. From these “mechanical states” of the muscle, the neural inputs driving the specific motor behaviors of the UES can be inferred. In this study we compared predictions of UES mechanical states directly with the activity measured by electromyography (EMG). In eight subjects, pharyngeal pressure and impedance were recorded in parallel with CP- and SM-EMG activity. UES pressure and impedance swallow profiles correlated with the CP-EMG and SM-EMG recordings, respectively. Eight UES muscle states were determined by using the gradient of pressure and impedance with respect to time. Guided by the level and gradient change of EMG activity, mechanical states successfully predicted the activity of the CP muscle and SM muscle independently. Mechanical state predictions revealed patterns consistent with the known neural inputs activating the different muscles during swallowing. Derivation of “activation state” maps may allow better physiological and pathophysiological interpretations of UES function

Manometric demonstration of duodenal/jejunal motor function consistent with the duodenal brake mechanism

© 2020 John Wiley & Sons Ltd Background: High-resolution manometric studies below the stomach are rare due to technical limitations of traditional manometry catheters. Consequently, specific motor patterns and their impact on gastric and small bowel function are not well understood. High-resolution manometry was used to record fed-state motor patterns in the antro-jejunal segment and relate these to fasting motor function. Methods: Antro-jejunal pressures were monitored in 15 healthy females using fiber-optic manometry (72 sensors at 1cm intervals) before and after a high-nutrient drink. Key Results: Postprandial motility showed a previously unreported transition point 18.8cm (range 13-28cm) beyond the antro-pyloric junction. Distal to the transition, a zone of non-propagating, repetitive pressure events (11.5±0.5cpm) were dominant in the fed state. We have named this activity, the duodeno-jejunal complex (DJC). Continuous DJC activity predominated, but nine subjects also exhibited intermittent clusters of DJC activity, 7.4±4.9/h, lasting 1.4±0.55minutes, and 3.8±1.2minutes apart. DJC activity was less prevalent during fasting (3.6±3.3/h; P=.04). 78% of fed and fasting state propagating antro-duodenal pressure events terminated proximally or at the transition point and were closely associated with DJC clusters. Conclusions and Inferences: High-resolution duodeno-jejunal manometry revealed a previously unrecognized transition point and associated motor pattern extending into the jejunum, consistent with the duodenal brake previously identified fluoroscopically. Timing suggests DJC activity is driven by chyme stimulating duodenal mucosal chemosensors. These findings indicate that the duodenum and proximal jejunum consists of two major functional motor regions

Paediatric and adult colonic manometry: A tool to help unravel the pathophysiology of constipation

Colonic motility subserves large bowel functions, including absorption, storage, propulsion and defaecation. Colonic motor dysfunction remains the leading hypothesis to explain symptom generation in chronic constipation, a heterogeneous condition which is extremely prevalent in the general population, and has huge socioeconomic impact and individual suffering. Physiological testing plays a crucial role in patient management, as it is now accepted that symptom-based assessment, although important, is unsatisfactory as the sole means of directing therapy. Colonic manometry provides a direct method for studying motor activities of the large bowel, and this review provides a contemporary understanding of how this technique has enhanced our knowledge of normal colonic motor physiology, as well as helping to elucidate pathophysiological mechanisms underlying constipation. Methodological approaches, including available catheter types, placement technique and recording protocols, are covered, along with a detailed description of recorded colonic motor activities. This review also critically examines the role of colonic manometry in current clinical practice, and how manometric assessment may aid diagnosis, classification and guide therapeutic intervention in the constipated individual. Most importantly, this review considers both adult and paediatric patients. Limitations of the procedure and a look to the future are also addressed