Simulation And Experiment Research On Multichannel Measurement Method Of Impedance Gastric Motility

Impedance gastric motility measurement is a method to extract biomedical information associated with gastric motility according to the electrical property of the stomach during the process of digestion. It injects a small current and tests the impedance from electrodes on the body surface. The method has the advantages of being noninvasive, convenient, and providing considerable functional information, and can be used for clinical monitoring. But impedance gastric motility measurement is an indirect test method, and the quantitative relationship between impedance signal and gastric motion is unknown and needs to be explored further. Single channel measurement of impedance gastric motility commonly used at present only reflects the average impedance changes of the gastric motion, and can not reflect the contraction in different regions of the stomach and the peristalsis signal propagation from gastric body to pylorus. In this paper, using simulation and experiment, we study the measurement mechanism of multi-channel impedance gastric motility method.1. The cylinder and the bend models are established using COMSOL multiphysics software to simulate the conductivity distribution of stomach and its variation during the process of gastric motion, and the forward problem is solved. The results show that in both injection and measurement patterns of axial and radial direction, the amplitude of the impedance can reflect the variation of the gastric content in conductivity and volume. The relationship between them is nonlinear. When the smooth muscle of the stomach contracts from the pacemaker to the pylorus, the frequency of the impedance signal is equal to the contraction frequency of the model. There is phase shift between measured waves of adjacent channels, and it reflects gastric contraction and the propagation of the peristalsis. The simulation results show that the frequency of the multi-channel impedance signal reflects the contraction rhythmic in different regions of stomach, and the amplitude of the signal is related to the conductivity, volume and contraction extent of the stomach. When the conductivity of the gastric content is higher or lower than that of the background, the relative impedance signals in both conditions followed the same variation trend, but in opposite direction, and is not show a simply negative relationship. 2. A multi-channel impedance measurement system and a specially designed experiment device are built to conduct experiments for gastric motion simulation. The device includes a tank filled with salt solution, some agar models and mechanical movement parts. The results show that the multi-channel impedance signal can reflect the movement progress of targets with different conductivity and shape. The experiments have confirmed the simulation results and provide a scientific basis for the impedance gastric motility method.3. The impedance gastric motility signal of single channel measurement and synchronous electrogastrogram, from20patients with erosive gastritis are collected and denoised using wavelet transform method. The wavelet energy entropy of the signals is calculated and proposed as feature vector to a BP neural network classifier. The experiment results demonstrate that the wavelet energy entropy of the most patients decreased after one week treatment and the recognition rate of the BP neural network is80%. The result suggests that wavelet energy entropy can describe the energy distribution complexity of gastric signals in both time and frequency domains and provide a new and sensitive parameter to the therapeutic evaluation of gastroenteropathy patients.