Abstract
BackgroundContractions and relaxations of the muscle layers within the digestive tract alter the external diameter and the internal pressures. These changes in diameter and pressure move digesting food and waste products. Defining these complex relationships is a fundamental step for neurogastroenterologists to be able define normal and abnormal gut motility.ResultsUtilising an in vitro technique that allows for the simultaneous recording of intraluminal pressure (manometry) and gut diameter (video) in an isolated section of rabbit colon, we developed a technique to help define the mechanical states of the muscle at any point in space and time during actual peristaltic movements. This was achieved by directly relating the changes in pressure to the changes in diameter along the length of the gut studied. For each individual measure of pressure or diameter, 3 dynamic state components were identified; increasing or decreasing changes or a stable period. Two additional static state components, fully contracted and fully distended, were defined for the diameter. Then qualitative mechanical states of the muscle activity were defined as combinations of these state components. A hidden Markov model was used to correlate adjacent-in-time samples, and the Viterbi algorithm was used to infer the most likely sequence of mechanical states based on the observed data. From this a spatiotemporal map of the mechanical states was produced, showing the regions of active contractions, active relaxations, or passive states along the length of the gut throughout the entire recording period.ConclusionsThe identification of mechanical muscles states based on gut diameter and intraluminal pressure was possible by modelling muscle activation with a hidden Markov model.
Highlights
Contractions and relaxations of the muscle layers within the digestive tract alter the external diameter and the internal pressures
*Correspondence: phil.dinning@flinders.edu.au †Equal contributors 1Discipline of Human Physiology, Flinders Medical Science and Technology, Flinders University, Adelaide, Australia 2Departments of Gastroenterology and Surgery, Flinders Medical Centre, Adelaide, Australia ability to define the relationship that exist between wall motion, intraluminal pressure and the flow of content is a fundamental step in understanding how altered motor patterns effect the transport of luminal content. Accurately defining these relationships in the human gut in vivo is problematic; ethical constraints prevent detailed examination of real-time movement of the gut wall. To overcome this problem we developed an in vitro animal preparation that allowed us to record simultaneously, both intraluminal pressure and gut diameter in real time, across varying length (15–90 cm) of intestine [3] (Figure 1a,b)
In the stage of this research we published a theory based paper in which we developed a strategy based on simple principle of biomechanics to deduce the mechanical state of the muscle by calculating the relation between pressure and diameter at every point along the gut segment, and establishing where and when the muscle is actively contracting or relaxing [4] (Figure 1c,d)
Summary
Contractions and relaxations of the muscle layers within the digestive tract alter the external diameter and the internal pressures These changes in diameter and pressure move digesting food and waste products. The movement of content results from a complex series of muscular contractions and relaxations These movements of the gut wall alter the pressure profiles within the gut [1] which in-turn cause the digesting contents to move in an oral or anal direction. Abnormalities in these motor patterns are associated with several prevalent and unpleasant disorders that cost health care systems billions of dollars per year [2].
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