Measurement system for electrical impedance and EGG

This paper describes a measurement system measuring electrical impedance signal and synchronous electrogastrogram (EGG). Electrical impedance signal is measured with the conventional tetrapolar method. Two outer electrodes insert 2 mA, 50kHz constant current on epigastric surface of body, and voltage is measured using inner two electrodes. In this paper, ADuC834 was selected to collect the low-frequency gastric impedance signal and the series control SPCOMM was employed to sample the signal from the ADuC834. Both signal collected from body surface are off-line decomposed by multi-resolution analysis. Wavelet transform is addressed to separate the electrical impedance signal from respiratory artifacts and blood flowing artifacts. We did some experiment to test the quality of this measurement system in clinical conditions and research the gastric motility and gastric emptying in time domain and frequency domain. According to preliminary experiment, the system has good performance in measurement precision. The result showed that ADuC834 is suitable for extracting the low frequency gastric impedance signal and wavelet transform have good performance to get rid of the interference.