New Insights into Gastric Pressure Activity

Diseases in the gastric cavity are, to some extent, related to with gastric motility. Using a telemetric device, which is composed of a capsule robot, an in-vitro pocket data recorder, an ultrasonic locating unit, and an in-vitro data processing computer, to obtain gastric physiological digestive or interdigestive pressure activity is a good way to get the pattern of gastric motility. This chapter of the book first presents such a telemetric device. Then, general data processing and analysis method, as well as reasonable interpretation on how to generate such gastric pressure activity are given. Such general process for processing pressure recordings includes removal of abnormal values, five-three-Hanning (53H) weighted average smoothing and estimation of pressure activity fluctuation frequency. Finally, an analysis method for detecting quadratic phase coupling (QPC) behavior of human gastric interdigestive pressure activity is proposed. They are the Fourier transforms of the diagonal slices of the triple correlations, and can actually detect the phase coupling and coupled components respectively by expanding the real process into the complex counterpart through Hilbert transform. In order to learn more about the QPC structure in a certain frequency band that we are mostly interested in and obtain higher frequency resolution, the method, named the wavelet packet based diagonal slice spectrum, is introduced. It shows that the nonlinear QPC behavior occurs during gastric contractions (phase II), whereas no distinct phase coupling occurs during gastric motor quiescence (phase I). It is the nonlinear cell-to-cell coupling mechanisms, existence of fast and slow waves and their interactions that nonlinear QPC structure of the gastric pressure activity occurs. These findings in this chapter could be considered as some new insights into gastric pressure activity.

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