Running spectrum analysis as an aid in the representation and interpretation of electrogastrographic signals

The recording of gastric myoelectrical activity by means of cutaneous electrodes attached to the external abdominal wall is termed electrogastrography. Respiration and motion artefacts hamper the interpretation of electrogastrographic signals. Running spectrum analysis, using the fast Fourier transform, seems to provide a concise spectral representation of electrogastrographic data. In this paper the concept of running spectrum analysis is presented in detail using test signals consisting of frequency modulated sine waves and actual recordings from dog and man. Especially the visual interpretable representation in appropriate plots is emphasised and discussed. It is demonstrated that tachygastrias with a duration of the order of 30s can easily be recognised in the spectra. In most cases the gastric frequency can be recognised in the spectra. It is concluded, therefore, that running spectrum analysis has to be considered an attractive noninvasive method to study gastric myoelectrical activity in dog and man.