Infoscience

Thesis

Electrical and mechanical activity of the intestine: experimental assessment and biophysical modeling

The intestine is today still an organ whose mechanisms of functions are not fully understood. The diffculty in its understanding comes from the fact that it is regulated by a complex network of signals of different natures. Granting that a multitude of experimental techniques have brought precious information on the electrophysiological processes associated to the intrisic activity of the intestin, there is still shadow covering over the boundary of knowledge. With a view to sharpening the study of the complex spatio-temporal dynamics of the intrinsic electrical and mechanical activity of the intestine, three different numerical models of intestinal tissue were developed. Of particular interest are the networks of coupled oscillators, exhibiting a mass behavior with marked analogy to the intestinal tissue. The conception of these models were conducted by the handling of effective numerical methods and evaluation of numerical instability and errors. A simplified geometrical model of human colon was also developed, so as to allow a realistic visualization of the simulated results. Experimental measures in vitro and in vivo of an animal model, namely the pig, endorsed us the recordings of intrinsic electrical and mechanical activity of different intestinal segments. The recordings of the mechanical activity were obtained by three different tools: visual inspection, manometry, and Magnet Tracking. The first method implies the use of image processing for the evaluation of intestinal movement. The second one provides local pressure measurements. Only the third method enables noninvasive measurements along the digestive tube. In order to automate the extraction of valuable information contained in the signals recorded by the last method, an approch was proposed based on morphological filtering. These three methods of measure were also used in a parallel study to evaluate the electrical stimulation of the colon, with a goal to find an alternative solution to clasical treatments of chronic constipation. We showed that it is possible to induce local contraction in the cecum with electrical stimulation generated by an implantable device. Computer models guarantee at any time the realization of reproducible simulations of technically dicult, and even impossible, experiments. They compel, nonetheless, a simplification of the physiological reality. So as to validate the computer models, the result of simulations must be treated by particular methods. Electrograms and signals representing the mass movement were computed and faced to observations and real measurements. Simulated electrograms revealed a similarity to those recorded on animal intestines. Numerous resemblances are likewise observable between simulated signals of mass movement and the recordings of Magnet Tracking.

    Thèse École polytechnique fédérale de Lausanne EPFL, n° 3242 (2005)
    Section de génie électrique et électronique
    Faculté des sciences et techniques de l'ingénieur
    Institut de génie électrique et électronique
    Laboratoire de traitement des signaux 1
    Jury: Pavel Kucera, Jean-Jacques Meister, Juan Ramon Mosig, Nathalie Virag

    Public defense: 2005-6-10

    Reference

    Record created on 2005-04-06, modified on 2016-08-08

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