Three-dimensional static parametric modelling of phasic colonic contractions for the purpose of microprocessor-controlled functional stimulation

The study aimed at creating an integrated electromechanical model of invoke d phasic contractions in canine colon during direct high frequency voltage stimulation. The model utilized data obtained from two large anaesthetized dogs that underwent laparotomy and serosal implantation of two circumferent ial electrode fairs into a distal segment of the left colon. The strength d istribution of the stimulating electric field was analysed over a cylindric al mesh-surface grid modelling the interrogated colonic segment. Recordings of the stimulating current were utilized to model smooth, muscle depolariz ation using linearized macroscopic tissue conductivity. The invoked contrac tile stress was related to the stimulating electric field strength using an exponential sigmoid function. Artificially produced occlusion of the lumen was derived for a pair of 5 mm electrodes positioned on a cylindrical mesh -surface of 2 cm diameter and 15 cm length. The model simulated contraction s invoked by stimuli of different amplitude (up to 12 V) with 98.6% accurac y of approximation. Macroscopic tissue conductivity was modelled as a combi nation of two first-order exponential terms involving a 3 ms time constant. Real-time simulation of the current drawn by the smooth muscle during 10 V /50 Hz bipolar voltage stimulation was performed. The integrated electromec hanical model facilitates the quantification of microprocessor-controlled p hasic colonic contractions.