Design of a Simulation Toolbox for Gastrointestinal Electrical Activity n BME 273: Senior Design Projects n John F Gouda n Advisor: Dr. Alan Bradshaw, Ph.D.

Motivation of Project n The living state physics group have state of the art equipment to measure the magnetic field of the intestine. n The magnetic field can be used to estimate the electric field: trans-membrane potential and slow currents. n Thus, the need arose for a simulation environment that allows the user to create a dynamics model of GI electrical activity.

Solution-Neutral Problem Statement n How can we make a simulation toolbox that can be used to simulate gastrointestinal (GI) electrical activity?

Design Specifications User Demands n The simulation toolbox should: n 1. Give the user an intuitive grasp of GI electrical activity n 2. Rely on an accurate model of GI electrical activity n 3. Rely on an intuitive model of GI electrical activity n 4. Relate model simulations with experimental data

Project Specifications User Wishes n If possible, the simulation toolbox should: n 1. Have a user-friendly interface n 2. Provide the user with “on the spot” calculations and metrics that represent the response of the model to the parameters supplied to the toolbox. Provide the user with a measure of goodness of fit with experimental data.

Wishes Continued n 3. Provide the user with “on the spot” graphics that represent the response of the model to the parameters supplied to the toolbox n 4. Provide the user with analysis modules that can analyze the complexity of GI activity and provide intuition into the physiologic function of GI tract.

Background n 1960 Nelson and Becker suggest that a chain of relaxation oscillators (RO) could simulate GI electrical activity. n 1971 Sarna et al. Used a modified version of the Van der Pol oscillator to simulate GI electrical activity n The name “relaxation oscillators” comes into place because the “stress” accumulated during the slow buildup is “relaxed” during the sudden discharge.

Core conductor models n The parameters of relaxation oscillators can not be directly related to physiologic parameters (i.e. ion channels and cell coupling). n Models based on ionic mechanisms of membrane activity and on symmetric electrical coupling of cells are called core conduction models.

Our model n We proposed a simple model that attempts to combine the mathematical utility and simplicity of relaxation oscillators and the physiologic intuition of core-conductor models. n Two muscle layers: longitudinal muscle (LM) and interstitial cells of Cajal (ICC) n The model consists of 4 (2 for each muscle layer) nonlinear coupled partial differential equations in time and space.

Current status of project n 1. A preliminary mathematical model was formulated. n 2. The modeling environment will be the differential equation editor interfacing with Simulink interfacing with Matlab. n 3. An initial prototype is currently being developed.

Budget n Need a Simulink manual?