An assembled electrogastrographic device to examine the meal effect on gastric slow wave

Electrogastrography measurement systems and analysis methods used in clinical practice and research: comprehensive review

Electrogastrography (EGG) is a non-invasive method with high diagnostic potential for the prevention of gastroenterological pathologies in clinical practice. In this study, a review of the measurement systems, procedures, and methods of analysis used in electrogastrography is presented. A critical review of historical and current literature is conducted, focusing on electrode placement, measurement apparatus, measurement procedures, and time-frequency domain methods of filtration and analysis of the non-invasively measured electrical activity of the stomach. As a result, 129 relevant articles with primary aim on experimental diet were reviewed in this study. Scopus, PubMed, and Web of Science databases were used to search for articles in English language, according to the specific query and using the PRISMA method. The research topic of electrogastrography has been continuously growing in popularity since the first measurement by professor Alvarez 100 years ago, and there are many researchers and companies interested in EGG nowadays. Measurement apparatus and procedures are still being developed in both commercial and research settings. There are plenty variable electrode layouts, ranging from minimal numbers of electrodes for ambulatory measurements to very high numbers of electrodes for spatial measurements. Most authors used in their research anatomically approximated layout with two++ active electrodes in bipolar connection and commercial electrogastrograph with sampling rate of 2 or 4 Hz. Test subjects were usually healthy adults and diet was controlled. However, evaluation methods are being developed at a slower pace, and usually the signals are classified only based on dominant frequency. The main review contributions include the overview of spectrum of measurement systems and procedures for electrogastrography developed by many authors, but a firm medical standard has not yet been defined. Therefore, it is not possible to use this method in clinical practice for objective diagnosis.

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Fasting and postprandial small intestinal slow waves non-invasively measured in subjects with total gastrectomy

BACKGROUND AND AIM

Slow wave is essential to initiate gastrointestinal tract motility. Subjects with total gastrectomy (TG) provide an opportunity to study small intestinal slow wave in the absence of stomach interference. The aims of this study were to determine the origin of 3 cycles per min (cpm) slow wave recorded via electrogastrogram (EGG) and the characteristics of putative small intestinal slow waves in TG subjects.

METHODS

Thirty-three subjects with TG (25 male, age: 44-83 years) were consecutively enrolled. In each subject, the myoelectricity-like signals of the gastrointestinal tract were recorded using 3-channel EGG. Fourier transform-based spectral analysis was performed to derive the EGG parameters including dominant frequency/power, % normal rhythm (2-4 cpm), and power ratio.

RESULTS

Neither visual nor spectral analysis of the EGG revealed any waves at a frequency of about 3 cpm. The most frequently observed peaks in the power spectra of all subjects were those at approximately 1, approximately 6 and approximately 11 cpm with occurrences of 97%, 6.1% and 90.9%, respectively. Based on visual analysis of all recorded signals, the approximately 11 cpm signal was exactly rhythmically recorded rather than the approximately 1 cpm. The recorded approximately 11 cpm wave had a frequency of 10.9 +/- 1.0 cpm in the fasting state and 10.9 +/- 1.3 cpm in the fed state (NS), and a power of 31.5 +/- 3.2 dB in the fasting state and 35.2 +/- 3.8 dB in the fed state (P < 0.0001). None of other factors, including sex, age, and body mass index, had any impact on this approximately 11 cpm wave.

CONCLUSIONS

Small intestinal slow wave can be recorded non-invasively using EGG via cutaneous electrodes in TG subjects. Sex, age and body mass index have no effect on the intestinal slow waves. The power rather than frequency of intestinal slow wave is increased after a solid meal.

Electrogastrography: basic knowledge, recording, processing and its clinical applications

The slow wave (SW) of the gastrointestinal (GI) tract mainly functions to trigger the onset of spike to elicit smooth muscle contraction, which provides the essential power of motility. Smooth muscle myogenic control activity or SW is believed to originate in the interstitial cells of Cajal (ICC). The electrical coupling promotes interaction between muscle cells, and ICC additionally contribute to SW rhythmicity. Stomach SW originates in the proximal body showing the continuous rhythmic change in the membrane potential and propagates normally to the distal antrum with a regular rhythm of approximately 3 c.p.m. A technique using electrodes positioned on the abdominal skin to pick up stomach rhythmic SW refers to electrogastrography (EGG). The stomach SW amplitude is very weak, while many visceral organs also produce rhythmic electricities, for example heartbeat, respiration, other organs of the GI tract and even body movements. Thus noise other than SW should be filtered out during the recording, while motion artifacts are visually examined and deleted. Finally, the best signal among all recordings is selected to compute EGG parameters based on spectral analysis. The latter is done not only to tranform frequency domain to time domain but also to provide information of time variability in frequency. Obtained EGG parameters include dominant frequency/power, % normal rhythm, % bradygastria, % tachygastria, instability coefficient and power ratio. Clinical experience in EGG has been markedly accumulated since its rapid evolution. In contrast, lack of standardized methodology in terms of electrode positions, recording periods, test meals, analytic software and normal reference values makes the significance of EGG recording controversial. Unlike imaging or manometrical studies, stomach motility disorders are not diagnosed based only on abnormal EGG parameters. Limitations of EGG recording, processing, computation, acceptable normal parameters, technique and reading should be known to conduct subjective assessments when EGG is used to resolve stomach dysfunction. Understanding basic SW physiology, recording methodology and indications may open EGG as a new domain to approach the stomach motor dysfunction.

Influence of various feeding conditions, the migrating myoelectric complex and cholinergic drugs on antral slow waves in sheep

The presented study was designed to elucidate whether the cholinergic mechanisms control ovine antral slow waves in various physiological conditions, including feeding and various phases of migrating myoelectric complex (MMC). The investigations were carried out on six adult sheep of Polish Merino breed with seven bipolar electrodes surgically implanted onto the antral and small intestinal wall. In the course of chronic experiments, the myoelectric activity was recorded from these regions using the multichannel electroencephalograph. Experiments were performed on 48 h fasted and non-fasted animals. During some of these experiments, sheep were fed with standard fodder. During control experiments 0.15 M NaCl was slowly administered i.v. through the indwelling catheter and during other experiment, hexamethonium bromide (2.0 and 5.0 mg/kg). atropine sulfate (0.02; 0.1; 0.5 and 1.5 mg/kg) and pirenzepine dihydrochloride (0.02; 0.5 and 2.0 mg/kg) were administered i.v. during phase 1-2a or 2b MMC. The drugs were also given in combinations. The recordings were analysed and the antral slow wave amplitudes and frequencies were calculated. Unlike the slow wave amplitude, either feeding or the anticholinergic drugs significantly increased slow wave frequency, especially when the given procedure was started during phase 2b MMC. The most pronounced effects were observed after hexamethonium given alone or in combinations. Thus, the cholinergic system modulates antral slow wave frequency in sheep.

An improved electrogastrographic system in measuring myoelectrical parameters

This study assessed the reliability of an improved electrogastrographic (EGG) system in recording stomach myoelectrical parameters and tried to establish the normal ranges of myoelectricity using this system. The analytical software of the current system mainly included an autoregressive modelling program to compute myoelectrical frequency and power. Forty healthy subjects were enrolled to receive myoelectrical measurement in two consecutively fasting and one postprandial 30 min sessions. The myoelectrical frequencies in both fasting and postprandial sessions were almost three cycles per min (c.p.m.) and showed little variation. The percentage of dominant frequencies (2.5-3.5 c.p.m.) in three sessions was approximately 80% while the computed myoelectrical powers in the first and second fasting sessions exhibited a significant correlation (r=0.84, P<0.001). Meal ingestion increased the myoelectrical powers by 6.8dB compared with the second fasting recording (P< 0.001). The mean variation in myoelectrical amplitude for the ratio of second: first fasting session was 110.3+/-88.8% (16-478%, median 88%). This new EGG system is, indeed, reliable for measuring myoelectrical frequency and power, whereas the interassay of recorded amplitudes appears markedly variable.