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| Mechanistic Study of Multichannel Impedance Method for Gastric Motility Measurement |
| Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin 300192, China |
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Abstract The aim of this work is to investigate the relationship between multichannel electrical bioimpedance signals and propagation of gastric peristalsis wave, and obtain the measurement mechanism of the electrical impedance method for gastric motility. A cylindrical volume conductor model was built using COMSOL software. The contraction of gastric circular muscle and its propagation were simulated in this model. The voltage measured from boundary of the region was obtained by solving the forward problem of electromagnetic field. An experimental device including mechanical drive unit and threelayer agar models with different conductivity was made to simulate the stomach and its contraction, and the dynamic test was performed in a salt water tank. Under the axial and radial direction current excitation pattern, the waveform of boundary voltage shows the position of circular muscle contraction and the process of peristalsis propagation. The phase difference between voltage waveform of adjacent channel exists. In experiment result, the phase differences respectively are 9 s and 6 s under axial and radial direction current excitation pattern for the agar model with conductivity of 1.35 S/m. It is correlated with the position and spacing of the measurement electrodes. The boundary voltage variations follow the same trends but in opposite direction when the electrical conductivity of gastric content is higher or lower than that of the background. The voltage sensitivity and mean value of the channels close to excitation electrodes are relatively high when using parameter δ，〖AKU-〗 and Umax/Umin for quantitative evaluation. The multichannel electrical bioimpedance signals can reflect the conductivity changes of gastric content, the contracts in different region and the peristaltic wave propagation time effectively.
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