Discrete Laplacian recordings of the electroenterogram from abdominal surface in humans

The first aim of this study was to obtain the discrete Laplacian of the myoelectric small intestine signal (electroenterogram, EEnG) from bipolar recordings on the abdominal surface in humans. In addition, the objective was to identify the slow wave (SW) component of the EEnG in the estimated Laplacian, as well as to compare this signal with the bipolar surface recordings. It was carried out 8 recording sessions in 6 healthy volunteers. The discrete Laplacian of the surface potential was performed using Hjorth's Laplacian estimation method. In order to identify the SW component of the EEnG, an adaptive filter, which removes breath interference from abdominal surface recordings, was designed. After that, periodograms and their dominant frequency were obtained. The results show that this frequency, in all surface recording channels and in their corresponding Laplacian, ranges from 0.12 to 0.16 Hz (7.3 to 9.8 cycles per minute) inside of the SW frequency range, whereas the frequencies of the respiration ranges from 0.21 to 0.31 Hz (12.9-18.4 cpm). Furthermore abdominal surface Laplacian potential contains averaged SW, information unless any bipolar surface channel do not record properly this signal. Consequently EEnG surface recordings can become a low cost technique to study bowel motility non-invasively.