Electrogastrography Signal Research Articles

Gastric myoelectrical activity in neonates of different gestational ages by means of electrogastrography.

to describe the patterns of the gastric myoelectrical activity, pre-and postprandially, in clinically stable neonates of different gestational ages, during their first two weeks of life by means of Electrogastrography. Electrogastrography was recorded in forty-five clinically stable neonates of different gestational ages (group I: 15 neonates of > 37 weeks, group II: 15 premature neonates of 32-37 weeks; Group III: 15 premature neonates of 28-31 weeks) receiving intermittent enteral feedings during their first two weeks of life. Electrogastrography recordings were performed for 1 hour pre-and postprandially. The Electrogastrography signal was recorded using the portable MicroDigitrapper Electrogastrography recording device and after motion artifacts were deleted, the remaining Electrogastrography data were submitted to quantitative analysis based on the "Running Spectrum Analysis". The percentages of normogastria, pre-and postprandially were greater than the percentages of gastric dysrythmias in all three studied groups. Furthermore, all neonates had the mean values of the Electrogastrography dominant frequency predominantly within the normogastria range, in both periods analyzed. There were no significant differences in the relative change of the Electrogastrography dominant power among the groups. This study demonstrates that the Electrogastrography patterns are similar between premature and full term neonates during the pre-and postprandial periods. The results of this study also indicate that the gastric myoelectrical activity in premature and full term neonates is immature, as compared to that described for older neonates, children and adults.

MICROCONTROLLER-BASED EGG RECORDING SYSTEM

An Electrogastrography (EGG) recorder is proposed in this paper. This recorder consists of a microcontroller, an interfacing circuit for the RS-232, amplifiers and filters for signal conditioning, and a control program for EGG acquisition. An EGG signal, filtered between 0.015 and 0.5 Hz, was used to evaluate the performance of this system. The results suggest that this system is useful both in the hardware circuits and in the analyzing software. The complete system is versatile and cheap. Thus, it will be helpful for other laboratories with limited financial budget. Furthermore, circuits are described in detail for this purpose.

Compressed time and frequency recording of the electrogastrogram by individual wave detection

Electrogastrography (EGG) is a method for recording and analysis of the bioelectrical activity of the stomach, acquired by cutaneous electrodes. The problem of obtaining an EGG signal as free of artefact as possible has recently found some solutions. Good quality recordings of several hours duration can be acquired, often needed, especially if clinical applications are envisaged. Therefore, a next problem to be considered would be time-compressed presentation of the EGG signal without loss of relevant signal characteristics. Relative amplitude changes can be of clinical value, while frequency variations are traditionally regarded as more important. A method for simple compressed presentation of long term EGG recordings, without losing information about the real amplitude and/or frequency changes or transients, is presented. It makes use of detection of successive wave extrema in an EGG. Successive wave amplitudes and durations are measured and momentaneous frequencies are derived. Then a compressed two-trace plot is generated, representing amplitude and frequency variations with respect to time. The method is virtually insensitive to baseline drift, as only the peak amplitudes are detected and followed. A compression factor with respect to the traditional signal recording (1 cm min-1 or 2 cm min-1 paper speed) of 5 up to 15 per trace can be obtained.

Usefulness of a developed four-channel EGG system with running spectrum analysis.

Electrogastrography (EGG) is a method of measuring action potentials on the abdomen. It is noninvasive, inexpensive and easy to measure. However, the EGG signal has a very low frequency (0.05 Hz) and an extremely low amplitude (10-100 microV). Consequently, its measured waveform is difficult to analyze and it is not yet completely understood. In this study, a four-channel EGG measurement system was built to measure the action potential of the stomach. This system was compared with the commercially available one-channel Digitrapper EGG. The 3 cpm percentages were compared between the best channel of the four-channel system and channel 1, whose electrode position was similar to the commercially available one-channel system for normal subjects. The average 3 cpm percentage of the best channel and channel 1 for preprandial measurement was 89.5% and 83.2%, respectively, and this was statistically significant (p < 0.001). Also the average 3 cpm percentage of the best channel and channel 1 for postprandial measurement was 90.4% and 76.5%, respectively, and this was statistically significant (p = 0.003). From these results, it can be concluded that a multi-channel EGG system is required for better EGG measurement.

Nonlinear adaptive noise compensation in electrogastrograms recorded from healthy dogs.

Adaptive noise compensation is a popular method for improving signal-to-noise ratio in a variety of biomedical applications with its major disadvantage being the requirement for a reference channel containing noise strongly correlated to the noise in the primary channel. In many biomedical applications the utilization of a channel containing such noise without any representation of the information signal is difficult if not impossible. In this study we investigated the possibility of applying adaptive compensation in nonideal noise environments containing substantial presence of information signal in the reference channel. The signal in the reference channel was subjected to nonlinear manipulations for reducing the signal-to-noise ratio, thus diminishing the representation of information signal. The methodology was tested on canine electrogastrographic (EGG) signals of four unconscious dogs which underwent laparotomy and implantation of six pairs internal stainless steel electrodes in addition to the eight-channel abdominal EGG. Fourteen-channel (six internal and eight cutaneous) were obtained from each dog for 1/2 h. The signals were digitized and processed by computer. All internal signals showed regular and coupled gastric electrical activity with frequency of repetition in the normogastric range [3-9 cycles-per-minute (cpm)]. A single pair of primary and reference channels was selected from each cutaneous recording and exponential manipulators in the reference channels were introduced. The manipulators were tuned to maximize the percent distribution of spectral components in the canine normogastric range of each frequency spectrum calculated from the signal at the output of the adaptive compensator. Significant increment in the percent distributions in the normogastric range (p < 0.01) was noted after tuning the exponential manipulator, and in many frequency spectra the recovery of the genuine dominant frequency peak of gastric electrical activity as determined by the internal recordings was noted. This study indicated that low percent distributions registered by some EGG channels are related to external nonlinear factors, the impact of which can be partially compensated.

Pitfalls in the analysis of electrogastrographic recordings

Electrogastrography (EGG) is a noninvasive method to study gastric myoelectrical activity in humans. Because frequency characteristics are the most reliable parameters and visual analysis of the EGG recordings is notoriously difficult, automated frequency analysis, especially running spectrum analysis, is often used. However, EGG frequency spectra can be misinterpreted easily. Movement artifacts and noise from various sources can result in abnormal frequency spectra with significant power in the low-frequency and high-frequency range, or even make the EGG completely uninterpretable. Signals that differ from a sinusoid waveform have harmonics in the high-frequency range of the spectrum and may be interpreted as abnormal. Visual inspection of raw signals and frequency spectra remains essential in the analysis of EGG signals. The value of computerized analysis should not be overrated. EGG is an important research tool, but a clinical role still needs to be established.

Continuous wavelet analysis as an aid in the representation and interpretation of electrogastrographic signals.

This paper presents an application of the continuous wavelet transform (CWT) in the analysis of electrogastrographic (EGG) signals. Due to the nonstationary nature of EGG signals, the CWT method, which uses multiresolution scaled windows, gives a better time-frequency resolution than the short-time Fourier transform, which uses a fixed window. Spike activity due to gastric contraction was investigated through experiments on dogs. During spike activity we observed an increase in magnitude of the slow wave and the appearance of a low frequency component with half the frequency of the slow wave. Studies of the EGG signals from the small intestine are also presented to investigate the hypothesis that its slow wave might be confounded with spike activity in the stomach due to the similarity of their frequency ranges.

Electrogastrography in healthy children: evaluation of normal values, influence of age, gender, and obesity.

Electrogastrography (EGG) is a reliable technique to record gastric electrical activity. However, the normal values of electrical activity in children and the effects of age, gender, and body mass index (BMI) are not well defined. To evaluate these items, EGG signal was picked up before and after a meal in 114 healthy children (age range: 6-12 years) by means of a pair of cutaneous electrodes sonographically placed on the abdominal surface. The dominant frequency was prevalently found in the 2.0-4.0 cpm range (P < 0.001). A significant difference was found comparing the pre- and postprandial instability coefficient of dominant frequency (P < 0.05). The EGG power increased postprandially (power ratio = 3.6), and the power ratio was not correlated to the approach of the wall of the gastric antrum to the abdominal surface (Spearman r = 0.0045, NS). In obese children, the postprandial pattern in response to a mixed test meal containing carbohydrate as the major caloric source was similar to that recorded in normal-weight children. EGG parameters were not affected by age and gender apart from a significant difference in the postprandial instability coefficient obtained from the "girls > or = 9 years" group compared to the "girls <9 years" and "boys > or = 9 years" groups (P < 0.05). In conclusion, in children 6-12 years old, EGG parameters are not affected by BMI in response to a mixed test meal. Gastric electrical rhythm and rate, and gastric power are not influenced by age and gender, whereas the instability coefficient seems to be influenced by these factors. The normal values of the EGG parameters evaluated in this study should be introduced in the analysis of gastric electrical activity for an effective interpretation of the EGG signal from children with functional or organic diseases.

Electrogastrography: a noninvasive technique to evaluate gastric electrical activity.

Electrogastrography (EGG) is the recording of gastric electrical activity (GEA) from the body surface. The cutaneous signal is low in amplitude and consequently must be amplified considerably. The resultant signal is heavily contaminated with noise, and visual analysis alone of an EGG signal is inadequate. Consequently, EGG recordings require special methodology for acquisition, processing and analysis. Essential components of this methodology involve an adequate system of digital filtering, amplification and analysis, along with minimization of the sources of external noise (random motions of the patient, electrode-skin interface impedance, electrode bending, obesity, etc) and a quantitative interpretation of the recordings. There is a close relationship between GEA and gastric motility. Although it has been demonstrated that EGG satisfactorily reflects internal GEA frequency, there is not acceptable correlation with gastric contractions or gastric emptying. Many attempts have been made to relate EGG 'abnormalities' with clinical syndromes and diseases; however, the diagnostic and clinical value of EGG is still very much in question.

Do increased electrogastrographic frequencies always correspond to internal tachygastria?

This study was undertaken to investigate the possible origin of some cutaneously recorded higher frequency electrogastrographic signals. Computer modeling of gastric electrical uncoupling was performed using previously described conoidal dipole model. Cutaneous electrogastrograms were simulated after uncoupling was introduced. In separate, real-life experiments, 6 pairs of bipolar electrodes were inserted into the gastric wall (3 anterior, 3 posterior) of 15 anesthetized dogs at laparotomy to record 6 channels of internal gastric electrical activity (GEA). Eight-channel bipolar cutaneous electrogastrography (EGG) was simultaneously recorded. Three separate 1/2-hr recordings were made from each dog in the basal state and after each of two circumferential cuts of all gastric muscle. Distal stomach was surgically divided into three equal-sized areas, each with an electrode pair in its anterior and posterior walls. Gastric electrical activity and EGG were digitized, bandpass-filtered and analyzed in frequency domain using the fast Hartley transform. The phenomena of tachygastria and tachyarrhythmia were quantitatively compared in internal and cutaneous recordings. Computer modeling indicated that it is possible to record cutaneous "tachygastric" or "tachyarrhythmic" signals without them being present internally. Real experiments on dogs showed higher percentage of tachyarrhythmia in EGG than in the internal signal in the basal state. After the first circumferential cut, the periods of tachygastria and tachyarrhythmia increased, with EGG signals showing again a higher percentage. This tendency persisted after the second circumferential cut. A similar pattern was observed when monitoring the percentage of uncorresponding tachygastrias/tachyarrhythmias. Our findings indicate that gastric electrical uncoupling can be another possible reason for abnormal frequency characteristics of EGG. Not all cutaneously recognized tachygastrias and/or tachyarrhythmias could be related to objectively existing internal tachygastric events.

60 DERANGEMENT OF GASTRIC ELECTRICAL ACTIVITY IN PRETERM INFANTS DURING ILLNESS.

Since vomiting due to gastric retention is a common feature in ill preterm infants and gastric motility is closely related to the electrical activity (EA) of the smooth muscle cells, we wished to measure EA of the stomach by electrogastrography (EGG) in 26 premature infants (gestational age range: 26-36 weeks), 16 without disturbances of organ systems (“healthy” preterm infants), 10 with disease processes and episodes of vomiting (“ill” preterm infants) (6 with disorders of the respiratory tract and 4 with sepsis). The EGG signals were recorded by 2 cutaneous Ag/AgCl electrodes placed sonographically on the skin overlying the gastric antrum with a third electrode as a reference. The EGG recording was performed 1 hour fasting and 1 hour after feeding an appropriate formula according to the preterm requirements. Data were analysed with the fast Fourier transformation. The following parameters were measured: 1)% of dominant frequency (DF) in different ranges (2-4 cpm: normal range; >4 ≤9 cpm: tachygastria; <2 cpm: bradygastria), during total (fasting and fed) recording period; 2) fed/fasting ratio of dominant power (power ratio); 3) fed/fasting instability of the dominant frequency (DFIC: dominant frequency instability coefficient). EGG data were compared with those recorded in 10 full-term newborns. Results: EA data are reported as follows (mean±SD): Table Conclusions: patterns of gastric EA in healthy preterm infants are similar to those detected in full-term babies; however, marked derangement of fasting and post-feeding electrical activity of the stomach occurs in preterm infants affected by disorders of organ systems. These abnormalities can underlie the gastric retention and vomiting observed in prematurity during illness.

Comparison of three running spectral analysis methods for electrogastrographic signals

Comparison of three running spectral analysis methods for electrogastrographic signals

Myoelectrical activity of the Billroth II gastric remnant.

This study was undertaken to investigate the extent to which gastric electrical control activity and phasic contractile activity are preserved after Billroth II resection and to assess the relation between these activities and postprandial symptoms in patients who have undergone Billroth II resection. Thirty three patients were studied after Billroth II resection without vagotomy. Gastric electrical activity was recorded from surface electrodes and intraluminal pressure was recorded simultaneously. The electrogastrographic signals were analysed by Running Spectrum Analysis. In addition, three dogs with a Billroth II stomach and implanted serosal electrodes were studied. Phasic gastric pressure waves were observed in most patients. Electrogastrographic signals recorded from 82% of the Billroth II patients contained a mean (SD) peak at 3.1 (0.2) cycles per minute (cpm). Fasting and postprandial frequencies correlated significantly (p less than 0.02) with the score for nausea and vomiting. In 61% of the patients, the electrogastrographic signal contained a stable component with a frequency of 10.5 (0.6) cpm that was not caused by respiration. We suggest that this activity is of intestinal origin. In all three dogs studied, retrograde conduction of jejunal electrical control activity (16 cpm) into the distal part of the gastric remnant was observed. In the Billroth II patients, the presence of a 10 cpm component correlated negatively with symptoms.

Myoelectrical Activity of the Stomach in Gastric Ulcer Patients: An Electrogastrographic Study

This study of gastric ulcer patients examined whether characteristic abnormalities in the fasting and postprandial gastric myoelectrical activity could be discerned electrogastrographically and whether these abnormalities, if present, were related to ulcer characteristics and complaints of nausea and vomiting. A total of 61 recordings were made in 31 gastric ulcer patients, both at the time of diagnosis and after ulcer healing, and these were compared to 52 recordings made in 52 control subjects. Several types of abnormal gastric myoelectrical activity were found in patients with an active ulcer: 1) instability of both the fasting and postprandial gastric frequency; 2) absence of the normal postprandial amplitude increase in the electrogastrogram; 3) waveform changes in the electrogastrographic signal in both the fasting and postprandial states; and 4) tachygastrias. These abnormalities were predominantly found in ulcer patients with symptoms of nausea and vomiting. They disappeared with ulcer healing and resolution of nausea and vomiting. These findings indicate that the abnormalities in gastric myoelectrical activity found in gastric ulcer patients are not merely due to the presence of the ulcer itself, but are associated with the presence of nausea and vomiting.

Electrogastrography: Clinical Applications

Electrogastrography (EGG) is defined as the recording of myoelectric activity of the smooth muscles of the stomach by means of cutaneous electrodes attached to the epigastric skin. Although the origin of the electrogastrogram is clear, the interpretation of the ‘raw’ electrogastrographic signal is problematic. To overcome this problem, running-spectrum analysis was introduced. After defining the electrogastrographic characteristics of the gastric myoelectric behaviour in healthy subjects, and an attempt had been made to identify the different phases of the interdigestive migrating complex, several patient groups were studied. The abnormal myoelectric activity found was characterized by: 1) unstable gastric frequency; 2) tachygastrias; and 3) abnormal postprandial amplitude behaviour of the gastric frequency. This abnormal myoelectric activity was correlated with nausea and vomiting and a delayed gastric emptying for solids. It was concluded that EGG can be regarded as a powerful non-invasive tool for the ...

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.

Glucagon-evoked gastric dysrhythmias in humans shown by an improved electrogastrographic technique

The objective of this study was to improve recording techniques for the recognition of gastric electrical dysrhythmias, and to explore the potential of pharmacologic agents to “evoke” gastric dysrhythmias. Eighteen healthy volunteers participated in 22 individual recordings, divided into two separate studies—a dose-response study and a randomized, double-blind study. The internal or mucosal electrogastrogram was recorded with a novel approach, using magnetic force to maintain internal electrodes in apposition with the gastric wall, whereas the external or cutaneous electrogastrogram, manometric activity, and respiration were measured by conventional methods. Analysis of simultaneous internal and external electrogastrographic signals, including both dysrhythmia and dysrhythmia-free intervals, revealed a good correspondence between the internal and external signals. In the dose-response study, 5 of the 6 volunteers intravenously infused with glucagon, in doses ranging from 3 to 22 μg/kg, developed gastric electrical dysrhythmias. In the randomized, double-blind study, 4 of 5 volunteers intravenously infused with glucagon (7 μg/kg) developed gastric dysrhythmias that were recognized by our improved techniques. Dysrhythmias, defined by visual analysis, consisted either of “tachygastria” (≥6 cycles/min for ≥1 min) or “bradygastria” (≥1 cycle/min for ≥1 min) and were evident on both internal and external electrogastrograms. Dysrhythmias were usually associated with absence of antral phasic pressure activity and frequently with nausea.

Contraction-related, low-frequency components in canine electrogastrographic signals.

Interdigestive gastric contraction-related phenomena were studied in four healthy conscious dogs by running-spectrum analysis of signals derived from the abdominal surface. When groups of contractions occur irregularly spaced in time, low frequencies (in the range below 0.085 Hz) show up in the power spectra of the electrogastrograms. It has been hypothesized that prolonged electrical control activity (ECA) intervals shown to coincide with irregular contractions are related in some way to these low frequencies. This hypothesis was investigated in detail. Whereas a certain degree of correlation was demonstrated between ECA interval variations, contractile activity, and the presence of low frequencies in the spectra obtained from electrogastrograms recorded during interdigestive migrating complexes, a more pronounced correlation between these phenomena was found during "minute rhythms." It was concluded that the presence of lower frequencies ranging from the normal gastric one to about 0.01 Hz in the running-spectrum representation of electrogastrograms recorded in fasting dogs is indicative of strong antral contractions and that the mechanism through which this is brought about involves prolongation of ECA intervals associated with these contractions.

Optimal direction of the electrogastrographic signal in man.

The study aims at determining a characterising configuration useful in obtaining the gastric signal of man from cutaneous electrodes. To do this, a daisy-chain electrode was placed on the abdominal surface making sure that a configuration was on the direction of the antral axis previously defined. The study is based on the analysis of the electrical signals recorded from 13 healthy subjects whose antrum position had been determined by X-rays. In the analysis the gastric signal amplitude was wider in the configuration corresponding with the antral axis than on other ones.

Adaptive filtering of canine electrogastrographic signals. Part 2: filter performance

The modified adaptive filter method described in Part 1 was applied to 16 stretches of (cutaneous) electrogastrographic signal of 17·07 min duration. A signal-to-noise ratio improvement of about 8 dB was achieved. The most characteristic feature of the filter method appeared to be that wave-form and phase of the gastric component of the electrogastrographic signal are preserved. It is concluded that the use of the modified adaptive filter forms a valuable tool in the study of the electrogastrographic signal.