Active Laplacian Electrode to Enhance Surface EEnG Recordings

The electroenterogram (EEnG) is the surface recording of the myoelectrical activity of the smooth muscle layer of the small intestine. Surface EEnG recordings in humans present many problems such as the low amplitude of the signals and the presence of physiological processes such as ECG and respiration. The aim of this study is to develop an active sensor to enhance the quality of the abdominal surface signals obtained by passive bipolar recordings. Moreover, this sensor could improve the approximation to the surface Laplacian of the electroenterogram signal given by applying Hjorth ´s five point approximation method. The sensor is made up by two parts. A set of three concentric ring electrodes in bipolar configuration (TCB) and a signal conditioning amplifier, which amplifies and high-pass filters the signals. This sensor has been made by using printed circuit boards and SMT technology. Two recording sessions were carried out in two healthy subjects. The results show that in the signal given by the TCB electrode the ECG interference is highly attenuated compared to bipolar recordings. Furthermore Laplacian TCB signals contain the information concerning to the SW component of the EEnG (9.7plusmn0.7 and 9.8plusmn0.8 cpm) reducing the influence of respiration compared to bipolar surface recording channels and to the discrete Laplacian approximation.