1288 IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 44, NO. 12, DECEMBER 1997 Reliability of Percent Distribution of Power of the Electrogastrogram in Recognizing Gastric Electrical Uncoupling Martin P. Mintchev,* Agnieszka Stickel, Stanislaw J. Otto, and Kenneth L. Bowes Abstract—The aim of this study was to examine the reliability of percent distribution of electrogastrographic (EGG) power in recognizing gastric electrical uncoupling. Sixteen anaesthetized dogs underwent laparotomy and implantation of six pairs of stainless-steel wire electrodes. Distal stomach was measured and three sections with approximately equal lengths were defined. Two pairs of electrodes were implanted in each section. Eight-channel EGG was also recorded. Three separate half-hour recordings were made: in the basal state; after a full circumferential separation of the distal antral section from the rest; after a second circumferential cut completely separating the middle from the proximal sections. EGG digital power spectra were split into three frequency ranges and dynamics of percent distribution of power was statistically examined. After the first cut, changes in the percent distribution of EGG power in the normal range were not significant . Significant changes in the low range were noted and changes in the high range were borderline nonsignificant . After the second cut, changes in percent distribution in the normal and the high range became significant while changes in the low range were insignificant . Severe uncoupling was reflected in EGG by significant changes in the high-frequency range without internal tachygastria necessarily being present. Index Terms—Electrogastrophy, gastric electrical uncoupling. I. INTRODUCTION The dynamics of the percent distribution of the frequency compo- nents in the electrogastrographic (EGG) power spectra was claimed to be a reliable representation of the dynamics of gastric electrical activity (GEA, [1]–[3]). However, no comparative study has been conducted to explicitly show that a shift of the EGG percent distri- bution toward higher or lower frequencies definitely means increased internal tachygastria or bradygastria [4], [5]. Moreover, it has been assumed that the dynamics of percent distribution would represent the dynamics of internal GEA frequency changes only. Gastric electrical uncoupling [6], a phenomenon which is far more likely to be related to an abnormal gastric function than occasional or even persistent frequency changes, could not be quantitatively evaluated from cutaneous EGG. The aim of this study was to examine the reliability of percent dis- tribution of EGG power in recognizing gastric electrical uncoupling. The study explored also the possibility that higher EGG frequency range could be affected by gastric electrical uncoupling alone, without higher-frequency GEA being present internally. II. METHODS Sixteen anaesthetized dogs underwent laparotomy and implantation of six pairs of internal stainless-steel wire electrodes. Gastric antrum Manuscript received October 11, 1996; revised June 12, 1997. Asterisk indicates corresponding author. *M. P. Mintchev is with the Department of Electrical and Computer Engineering, University of Calgary, 2500 University Drive N. W., Calgary, Alta. T2N 1N4 Canada (e-mail: mintchev@enel.ucalgary.ca). A. Stickel, S. J. Otto, and K. L. Bowes are with the Department of Surgery, University of Alberta, Edmonton, Alta. T6G 2B7 Canada. Publisher Item Identifier S 0018-9294(97)07605-2. (a) (b) Fig. 1. (a) Cutaneous and (b) internal electrode configurations used in the canine experiments. Internal electrodes a to f were implanted on the anterior gastric wall from the serosal side; electrodes g–l were implanted on the posterior wall. The first circumferential cut was performed along the line between electrode pairs e-f/l-k and c-d/i-j separating the distal from the proximal section. The second cut separated the electrode pairs a-b/g-h (the proximal section) from the middle section. was measured and three sections with approximately equal lengths were defined. Two pairs of electrodes were implanted in each section, one on the anterior and one on the posterior gastric wall from the serosal side. Eight-channel EGG was also recorded (Fig. 1). Three separate half-hour recordings were made: in the basal state; after a full circumferential separation of the distal antral section from the proximal stomach; after a second circumferential cut completely separating the middle from the proximal sections. EGG recordings were amplified, bandpass filtered (0.01–0.2-Hz, 2-pole Butterworth analog active filter), and digitized with 10-Hz sampling frequency using a locally designed multichannel electronic system. After the data acquisition, additional digital filtering was performed in the same frequency range and a new, lower sampling frequency of 2 Hz was introduced. Fast Hartley transform (a real-number equivalent of the fast Fourier transform, [7]) and a locally designed software system were used to convert successive 256-s intervals (75% overlap) from the time-domain EGG signals into frequency domain. EGG power spectra were split into three frequency ranges: low (0.1–3 cpm), normal (3–7 cpm), and high (7–18 cpm, Fig. 2). The percentage distribution of frequency power in the th frequency range ( for the low-frequency range, for the normal range, and for the high-frequency range) was calculated for each spectrum according to the following expression: (1) 0018–9294/97$10.00  1997 IEEE