ADAPTIVE CANCELLATION OF THE RESPIRATORY ARTIFACT IN SURFACE RECORDING OF SMALL-INTESTINAL ELECTRICAL-ACTIVITY

In the human small intestine there is omnipresent electrical activity with a frequency of 0.15-0.2 Hz. The electrical activity of the small intestine can be measured by surface electrodes placed on the abdomina l skin. The most annoying problem in the surface electrical recording is the respiratory artifact which is not discernible from the small in testinal signal. The frequency of the respiration is about 0.2-0.4 Hz, which is very casa to that of small intestinal activity, making the u se of the conventional bandpass filtering impractical. In this paper a selective frequency domain adaptive filter was proposed for the cance llation of the respiratory artifact. The basic principle of the select ive frequency domain adaptive filter is that only selected filter weig hts are adapted based on the frequency characteristics of the respirat ory artifact. Therefore, a substantial reduction of computation is ach ieved. A series of computer simulations was conducted for the optimiza tion of the system parameters and for the investigation of the system performance. It was demonstrated in this paper that the selective freq uency domain adaptive filter is as effective as, but more efficient th an, the conventional frequency domain adaptive filter. The adaptive sy stem for the cancellation of the respiratory artifact based on the sel ective frequency domain adaptive filter is very efficient in computati on, has a fast convergence (about 100 adaptations), substantial reduct ion of the respiratory artifact and little effect (or distortion) on t he small intestinal electrical signal.