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The following parameters were obtained: the dominant frequency (DF) of the signals, stability of the rhythm (RS) of the DF detected and the percentage of DFs within the typical frequency range for the SW (TFSW). Secondly, to identify the SW component of the EEnG, respiration interference was removed by using an adaptive filter, and spectral estimation techniques were applied. First, the ECG interference content present in the bipolar signals and in the Laplacian estimation were quantified and compared. Eight recording sessions were carried out on eight healthy human volunteers in a state of fasting.
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The objective was to analyze the enhancement given by Laplacian EEnG estimation compared to bipolar recordings. In this study, a discrete estimation of the abdominal surface Laplacian potential was obtained using Hjorth's method.
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However, surface EEnG recordings in humans present certain problems, such as the low amplitude of the signals and the influence of physiological interference such as the electrocardiogram (ECG) and respiration. Abdominal surface EEnG recordings could be a noninvasive solution for monitoring human intestinal motility. Most methods of studying bowel motility are invasive due to the difficult anatomic access of the intestinal tract. It is made up of two signals: a low-frequency component, known as the slow wave (SW), and high-frequency signals, known as spike bursts (SB). N2 - The electroenterogram (EEnG) is a surface recording of the myoelectrical activity of the smooth muscle layer of the small intestine. T1 - Identification of the slow wave component of the electroenterogram from Laplacian abdominal surface recordings in humans. This could be a useful non-invasive tool for monitoring intestinal activity by abdominal surface recordings. Furthermore, a slow frequency component, whose frequency, rhythm stability and amplitude fitted with the SW patterns in humans, was identified in bipolar and Laplacian estimation signals. In conclusion, it was demonstrated that the discrete Laplacian potential estimation attenuated the physiological interference present in bipolar surface recordings, especially ECG. Significant statistical differences were also found between the DF of all surface signals (bipolar and Laplacian estimation) and the DF of respiration. Furthermore in 80% of the cases, the detected DFs were inside the typical human SW frequency range, and the ratio of frequency change in the surface bipolar and Laplacian estimation signals, in 90% of the cases, was within the frequency change accepted for human SW. As regards the identification of the SW component of the EEnG, after removing respiration interference, the mean value of the DF in all abdominal surface recording channels and in their Laplacian estimation ranged from 0.12 to 0.14 Hz (7.3 to 8.4 cycles min(-1) (cpm)). Results show the better ability of the Laplacian estimation to attenuate ECG interference, as compared to bipolar recordings.
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The electroenterogram (EEnG) is a surface recording of the myoelectrical activity of the smooth muscle layer of the small intestine.