Dynamics of the level of randomness in gastric electrical activity

This study was undertaken to investigate the dynamics of the level of randomness in gastric electrical signals. Combined recordings of internal gastric electrical activity (GEA) and electrogastrograms (EGG) were obtained from 16 unconscious dogs and two postoperative patients. The signals were amplified using specially designed amplifiers with flexible frequency range and were digitized with 10-Hz sampling frequency. The 4.27-min portions of the digital signals were subjected to a previously described turning point test for randomness. The distributions of the number of turning points (NTP) in successive time intervals calculated from all GEA signals were compared to the estimated NTP distribution of a random signal. NTP dynamics of internal GEA signals was also correlated to the NTP dynamics of cutaneous EGG. In five of 16 recordings from the dogs and in two of the 14 recordings from the patients, NTP values calculated from some internal GEA channels exceeded the 1% probability level for entering the normal NTP distribution of a random signal (P > 0.01). In all measurements the distributions of the NTP values recorded from cutaneous EGG channels were significantly different (P < 0.01) from the NTP distribution of a random signal. There was significant correlation (P < 0.01) between the NTP dynamics of internal GEA and EGG. The level of randomness in internal GEA recorded with the short-distance bipolar technique is substantially higher than that in cutaneous EGG, probably due to the occurrence of spike activity. Although the level of randomness in EGG is affected by many external factors, its dynamics correlated significantly with the level of randomness in internal GEA.