Gastric Electrical Activity Research Articles

Relationship among gastric electrical activity, gastric emptying and intestinal permeability recorded in preterm newborns during the first month of life

Immaturity of motility, intestinal epithelial barrier function and absorptive capacity may play a role in the pathophysiology of intestinal diseases in preterms. We determined the gastric electrical activity and emptying, and intestinal permeability, in preterm newborns during the first month of life to verify the changes in motility and permeability, and their relationships.

Robust propagation velocity estimation of gastric electrical activity by least mean p-norm blind channel identification

The propagation of the gastric slow wave is one of the most important spatial characteristics of gastric electrical activity (GEA). The time delay estimation (TDE) is an effective approach to quantitatively assessing the propagation velocity of GEA. Traditional TDE analyses are developed under the condition reported that the background noise in GEA analysis is Gaussian distributed. Due to the effects of spikes and/or motion artifacts, the GEA obtained from gastric serosal electrodes often contains sharp transitions. This paper proposes robust time delay estimation based on least mean p-norm blind channel identification (BCILMP) under alpha-stable noise condition. Compared with the least mean square time delay estimation (LMSTDE), the BCILMP provides better performance in the impulsive noise environments. The robustness of the proposed method is demonstrated through computer simulations in both Gaussian and alpha-stable noise environments. The results of the propagation velocity of real data obtained from gastric serosal electrodes in gastroparetic patients show that the propagation velocity in gastroparetic patients is slower than in the normal subjects reported in the literature, and the slow-wave propagation is directed proximally to distally from the corpus toward the pylorus but not all the variability of the propagation velocity increases monotonously.

Gastric electrical activity and cardiovascular risk factors in relation to autonomic nervous function, hormonal responses, and health-related lifestyles in young men

Electrogastrography (EGG) is the noninvasive recording of gastric myoelectrical activity. The purpose of the present study was to assess associations of EGG with risk factors for cardiovascular disease (CVD), autonomic nervous function, hormonal responses, and health-related lifestyles. EGG was measured in 435 Japanese men, aged 24-39 years, who worked at the same company. In addition to anthropometric measurements and blood examinations, power spectral analysis of heart rate variability in low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.40 Hz) bands was conducted. LF/HF and HF were used as the indicators of sympathetic and parasympathetic nervous activity, respectively. Serum cortisol and catecholamine levels were measured as well. In univariate analyses, the EGG frequency was associated positively with the serum high-density lipoprotein (HDL) and cholesterol level (both-P < 0.0001) and negatively with age, body mass index (BMI), serum triglyceride level, fasting blood sugar, and diastolic blood pressure (all P < 0.05). The EGG frequency tended to increase with increases in the HF band (P = 0.10) and was not significantly associated with the LF/HF ratio (P = 0.45). Neither hormonal responses nor health-related lifestyle factors such as smoking and alcohol were significant (all P > 0.05). A multivariate analysis indicated that both the HDL cholesterol level and BMI were independent predictors of EGG frequency (both P < 0.05), after adjusting for the significant effects of age, HF, and other CVD factors. Slowed EGG frequency appeared to be linked with various CVD risk factors, including obesity and low HDL cholesterol levels, in young men.

Wavelet analysis of scaling properties of gastric electrical activity

We present a novel approach to the analysis of fluctuations in human myoelectrical gastric activity measured noninvasively from the surface of the abdomen. The time intervals between successive maxima of the wavelet transformed quasi-periodic electrogastrographic waveform define the gastric rate variability (GRV) time series. By using the method of average wavelet coefficients, the statistical fluctuations in the GRV signal in healthy individuals are determined to scale in time. Such scaling was previously found in a variety of physiological phenomena, all of which support the hypothesis that physiological dynamics utilize fractal time series. We determine the scaling index in a cohort of 17 healthy individuals to be 0.80 +/- 0.14, which compared with a set of surrogate data is found to be significant at the level P < 0.01. We also determined that the dynamical pattern, so evident in the spectrum of average wavelet coefficients of the GRV time series of healthy individuals, is significantly reduced in a cohort of systemic sclerosis patients having a scaling index 0.64 +/- 0.17. These results imply that the long-term memory in GRV time series is significantly reduced from healthy individuals to those with systemic sclerosis. Consequently, this disease degrades the complexity of the underlying gastrointestinal control system and this degradation is manifest in the loss of scaling in the GRV time series.

8 The effect of food on electrical and mechanical activity of the canine antrum

Background: Gastric electrical and mechanical activities are modulated by food, however, the pattern of food‐induced changes and the mechanisms governing them are not well defined.Aim: To characterize food–induced changes in gastric antral activity and to explore underlying mechanisms for such changes.Methods: Experiment 1‐ intended to test the effect of food on gastric signals. Two bipolar electrodes were implanted in the antrum of 7 mongrel dogs for simultaneous recording of slow wave rate, in events /min (SWR), and contractions assessed by electrical impedance (AI) in ohms. A strain‐gauge transducer was implanted in 3 dogs to correlate changes in AI with contractions. The meal consisted of a preload of 100 g of dry food followed in 10 min, by 900 g of the same food, to lengthen meal duration. SWR and AI were determined during 4 periods of 5 min/each (baseline, end of preload, satiety, 10 min after satiety). Experiment was repeated 5 times/dog. Experiment 2‐acute study, under anesthesia with 3 tests: 1) esophageal balloon distension 2) fundic balloon distension at volumes of 50–400 ml, using a balloon of 800 ml, and 3) nitroglycerin infusion, 0.5 (g kg­1 min­1 for 10 min. results as Mean ± SD.Results: Experiment 1‐ frequency of antral contractions by strain‐gauge correlated well with frequency of contractions as measured by AI, R = 0.76. SWRs at baseline, preload, satiety and post satiety were: 5.0 ± 0.3, 4.9 ± 0.4, 3.8 ± 0.65, and 4.4 ± 0.47 respectively. SW amplitudes (ohms) at the same periods were: 5.3 ± 1.4, 8.5 ± 2.1, 12.2 ± 4.3 and 12.0 ± 5.3 respectively; p &lt; 0.05 for satiety and post satiety vs. baseline for both measurements. Both changes peaked around the time of satiety. Mean time interval between satiety and slowest SWR was 80 ± 40 sec. Amplitude of contractions remained elevated for 212 ± 110 min after the meal. Experiment 2‐ fundic distension caused a transient decrease in SWR at lower volumes, but the decrease was sustained at the 400 ml volume, 3.9 ± 0.2 vs. 3 ± 0.8, baseline vs. distension, respectively, p = 0.002. NTG significantly reduced SWR: 4.0 ± 0.7 vs. 3.5 + 0.8, baseline vs. infusion, p = 0.007. Esophageal distension did not affect SWR.Conclusions: Food ingestion causes a significant decrease in SWR and significant enhancement of antral contractions that peak at satiety. This suggests a possible causal relationship that can be potentially useful when considering gastric electrical stimulation for modulation of satiety signals. Both gastric distension and nitrergic pathways affect SWR.

1 Gastric myoelectrical activity compared to pyloric pressure in patients with gastroparesis

Background: Gastric emptying is a function of gastric contraction, electrical activity, pyloric and duodenal resistance. Pylorospasm (basal pyloric pressures &gt;10 mmHg; Mearin et al. Gastro 1986) has been implicated in gastroparesis. Currently, pyloric pressures can be measured invasively, using a Dent sleeve (Mui Scientific, Inc.) manometry catheter. Electrogastrography (EGG) is a noninvasive tool for measuring gastric myoelectrical activity. EGG has been shown to distinguish gastric outlet obstruction from idiopathic gastroparesis (Brzana et al. Amer J Gastro 1998).Aims: The aims of this study were to 1) determine whether EGG can distinguish patients with gastroparesis who have pylorospasm and 2) correlate basal pyloric pressure with various EGG parameters.Methods and Results: 23 patients with gastroparesis (19 diabetics, mean age 40.4 ± 2.3, mean 4 hr gastric retention 43.0 ± 5.1%) had basal pyloric pressure measurements and EGG. Stationary basal pyloric pressures were measured using a Dent sleeve that was placed across the pyloric channel during endoscopy with fluoroscopic guidance. 60.9% (14/23) of patients had elevated pyloric pressures (21.8 ± 3.4 mmHg vs. 5.5 ± 0.8 mmHg). There was no difference in the postprandial power ratio and gastric emptying as measured by scintigraphy between the 2 groups. The fasting dominant slow wave frequency (SWF) in the elevated pyloric pressure group was significantly higher compared to the normal pyloric pressure group (3.1 ± 0.1 cpm vs. 2.4 ± 0.3 cpm; p = 0.013). There was significantly less dysrhythmia in the elevated pyloric pressure group (75.5 ± 6.0% normal rhythm vs. 54.8 ± 9.7% normal; p = 0.03). More patients in the elevated pyloric pressure group had normal fasting electrical rhythm (&gt;70% normal electrical rhythm) compared to the normal pyloric pressure group (64.3% vs. 22.2%; p = 0.03). There was a correlation between pyloric pressure and fasting slow wave frequency (r = 0.53, p = 0.005) but no correlation with the percentage of dysrhythmia, postprandial power ratio or gastric emptying.Conclusion: Patients with normal pyloric pressure and delayed gastric emptying have significantly more abnormalities in slow wave frequency and dysrhythmia compared to patients with abnormal pyloric pressure. This suggests that patients with delayed gastric emptying with normal pyloric pressures have abnormalities in gastric conduction as a cause of their gastroparesis.

37 Autonomic nervous system response to a solid meal in healthy children: its relation to gastric myoelectrical activity

Electrogastrogram (EGG) is a measurement of gastric electrical activity using cutaneous electrodes. Autonomic nervous function is an important modulator of gastric activity, but little is known regarding its relation with the EGG parameters. The aims of this study were to investigate the patterns of myoelectrical and autonomic activities both in the fasting and in the fed state and their correlation in healthy children.Methods: Simultaneous recordings of EGG and electrocardiogram were performed in 28 healthy children (13 M, 15 F, mean age: 12.4 years, range: 8–17) for 30 min in the fasting state and 60 min after a solid test meal. Spectral analysis was performed to compute EGG parameters and their postprandial changes. The autonomic activity was assessed based on spectral analysis of the heart rate variability (HRV) signal which was derived from the electrocardiogram. Data are presented as mean ± SE.Results: The solid meal resulted in a postprandial increase in the EGG dominant frequency (2.92 ± 0.08 cpm vs. 3.16 ± 0.07 cpm, P &lt; 0.05), dominant power (46.9 ± 0.8 dB vs. 53.7 ± 1.5 dB, P &lt; 0.05), and percentage of normal slow waves (81.9 ± 2.0% vs. 89.0 ± 2.0%, P &lt; 0.05). Spectral analysis of HRV revealed that sympathetic activity primarily associated with power in the low‐frequency band of HRV (LF) was increased in the postprandial state (0.34 ± 0.02 vs. 0.43 ± 0.03, P &lt; 0.05). The parasympathetic activity primarily associated with power in high‐frequency band of HRV (HF) was significantly higher in the fasting state (0.66 ± 0.02 vs. 0.58 ± 0.03, P &lt; 0.05). The sympathovagal balance associated with the LF‐to‐HF ratio was much higher in the postprandial state (0.56 ± 0.05 vs. 0.90 ± 0.13, P &lt; 0.05). Moreover postprandial LF was positively and HF was negatively correlated with the postprandial increase in EGG dominant power (r = 0.39; P = 0.04, respectively).Conclusions: The solid meal resulted in a significant increase in EGG dominant frequency, dominant power and percentage of normal slow waves as well as sympathovagal balance in healthy children, suggesting that both vagal and sympathetic pathways are involved in modulation of gastric myoelectrical activity.

Impaired gastric myolectrical activity in patients with cystic fibrosis

Background Cystic fibrosis (CF) is frequently associated with gastrointestinal complaints that can be due to gastrointestinal dysmotility. Electrogastrography (EGG) is an attractive, non-invasive procedure to assess gastric electric activity. The aims of our study were to investigate EGG abnormalities in pancreatic sufficient and pancreatic insufficient CF patients, and to examine whether EGG correlates with gastric emptying as assessed by scintigraphy. Methods EGG was performed in 23 CF patients (12 pancreatic sufficient patients, 11 pancreatic insuffficient) by using cutaneous recording pre- and postprandialy. Pre- and postpostprandial EGG indexes were compared to 19 healthy control patients. Gastric emptying was assessed simultaneously by gastric scintigraphy in 11 of the 23 CF patients. Six patients underwent a repeated scintigraphy recording following a month of treatment with cisapride. Results Abnormal patterns of EGG were found in 78.3% of CF patients compared to 31.3% of controls during fasting ( p ≤ 0.003) and in 56.5% of CF patients compared to 15.7% in healthy controls postprandially ( p ≤ 0.018). In the CF patients, dysmotility consisted mostly of bradygastria during both fasting (16 of 18 with abnormal EGG) and postprandially (12 of 13 [92.3%]). Gastric emptying results on scintigraphy were in agreement with EGG results in 9 of 11 (two normal and seven pathological). Five of the six patients treated with cisapride (83.3%) showed significant improvement in EGG indexes. Conclusions Our results suggest that EGG abnormalities are frequently found in CF patients. The similar rate of EGG and gastric scintigraphy abnormalities suggests that EGG may be a useful clinical tool in CF patients.

Biomagnetic characterization of spatiotemporal parameters of the gastric slow wave

Certain gastric disorders affect spatiotemporal parameters of the gastric slow wave. Whereas the electrogastrogram (EGG) evaluates electric potentials to determine primarily temporal parameters, fundamental physical limitations imposed by the volume conduction properties of the abdomen suggest the evaluation of gastric magnetic fields. We used a multichannel superconducting quantum interference device magnetometer to study the magnetogastrogram (MGG) in 20 normal human subjects before and after a test meal. We computed the frequency and amplitude parameters of the gastric slow wave from MGG. We identified normal gastric slow wave activity with a frequency of 2.6 +/- 0.5 cycles per minute (cpm) preprandial and 2.8 +/- 0.3 cpm postprandial. In addition to frequency and amplitude, the use of surface current density mapping applied to the multichannel MGG allowed us to visualize the propagating slow wave and compute its propagation velocity (6.6 +/- 1.0 mm s(-1) preprandial and 7.4 +/- 0.4 mm s(-1) postprandial). Whereas MGG and EGG signals exhibited strong correlation, there was very little correlation between the MGG and manometry. The MGG not only records frequency dynamics of the gastric slow wave, but also characterizes gastric propagation. The MGG primarily reflects the underlying gastric electrical activity, but not its mechanical activity.

Pre-Pyloric Neural Electrical Stimulation Produces Cholinergically-Mediated Reverse Peristalsis in the Acute Canine Model of Microprocessor-Invoked Gastric Motility for the Treatment of Obesity

Gastric Electrical Stimulation (GES) has been suggested as a new tool for the treatment of obesity. Among the known methods for GES, only Neural Gastric Electrical Stimulation (NGES) provides direct control of contractility without utilizing the spontaneously existing gastric electrical activity as an intermediary. However, only one of the established GES techniques, gastric pacing, has been described to produce retrograde peristalsis for delaying gastric emptying. The aim of this study was to explore the possibility of producing retrograde peristalsis using either single electrode set or dual electrode set NGES. 8 anesthetized dogs underwent laparotomy and implantation of 2 circumferential electrode sets approximately 3 cm and 7 cm proximal to the pylorus, respectively. Single-set and dual-set NGES sessions were repeatedly administered using a custom-designed implantable neurostimulator. Gastric motility patterns were captured using 3 force transducers implanted on the anterior gastric wall along the gastric axis. Motility indices and velocities were employed to quantify the produced contractile patterns. Both single-set and dual-set NGES produced circumferential lumen-occluding contractions in the vicinity of the electrode sets. The invoked contractions propagated proximally in a retrograde fashion. The propagation scope was different depending on the number of electrode sets used. Different velocities of the invoked retrograde contractions associated with single- and dual-set NGES were observed and quantified. Contractility patterns reflected by the normalized motility indices were very similar regardless of the electrode stimulation technique. Pre-pyloric NGES can produce controlled retrograde peristalsis and serve as another avenue for the treatment of obesity.

Multiscale modelling of human gastric electric activity: can the electrogastrogram detect functional electrical uncoupling?

During recent years there has been a growing interest in the assessment of gastric electrical health through cutaneous abdominal recordings. The analysis of such recordings is largely limited to an inspection of frequency dynamics, and this has raised doubts as to whether functional gastric electrical uncoupling can be detected using this technique. We describe here a computational approach to the problem in which the equations governing the underlying physics of the problem have been solved over an anatomically detailed human torso geometry. Cellular electrical activity was embedded within a stomach tissue model, and this was coupled to the torso using an equivalent current source approach. Simulations were performed in which normal and functionally uncoupled (through the introduction of an ectopic antral pacemaker) gastric slow wave activity was present, and corresponding cutaneous electrogastrograms were produced. These were subsequently analysed using the currently recommended techniques, and it was found that the functionally uncoupled situation was indistinguishable from normal slow wave activity using this approach.

Magnetogastrographic detection of gastric electrical response activity in humans

The detection and characterization of gastric electrical activity has important clinical applications, including the early diagnosis of gastric diseases in humans. In mammals, this phenomenon has two important features: an electrical control activity (ECA) that manifests itself as an electric slow wave (with a frequency of 3 cycles per minute in humans) and an electrical response activity (ERA) that is characterized by spiking potentials during the plateau phase of the ECA. Whereas the ECA has been recorded in humans both invasively and non-invasively (magnetogastrography—MGG), the ERA has never been detected non-invasively in humans before. In this paper, we report on our progress towards the non-invasive detection of ERA from the human stomach using a procedure that involves the application of principal component analysis to MGG recordings, which were acquired in our case from ten normal human patients using a Superconducting QUantum Interference Device (SQUID) magnetometer. Both pre- and post-prandial recordings were acquired for each patient and 20 min of recordings (10 min of pre-prandial and 10 min of post-prandial data) were analysed for each patient. The mean percentage of ECA slow waves that were found to exhibit spikes of suspected ERA origin was 41% and 61% for pre- and post-prandial recordings, respectively, implying a 47% ERA increase post-prandially (P < 0.0001 at a 95% confidence level). The detection of ERA in humans is highly encouraging and points to the possible use of non-invasive ERA recordings as a valuable tool for the study of human gastric disorders.

Artifact reduction in magnetogastrography using fast independent component analysis

The analysis of magnetogastrographic (MGG) signals has been limited to epochs of data with limited interference from extraneous signal components that are often present and may even dominate MGG data. Such artifacts can be of both biological (cardiac, intestinal and muscular activities, motion artifacts, etc) and non-biological (environmental noise) origin. Conventional methods—such as Butterworth and Tchebyshev filters—can be of great use, but there are many disadvantages associated with them as well as with other typical filtering methods because a large amount of useful biological information can be lost, and there are many trade-offs between various filtering methods. Moreover, conventional filtering cannot always fully address the physicality of the signal-processing problem in terms of extracting specific signals due to particular biological sources of interest such as the stomach, heart and bowel. In this paper, we demonstrate the use of fast independent component analysis (FICA) for the removal of both biological and non-biological artifacts from multi-channel MGG recordings acquired using a superconducting quantum intereference device (SQUID) magnetometer. Specifically, we show that the signal of gastric electrical control activity (ECA) can be isolated from SQUID data as an independent component even in the presence of severe motion, cardiac and respiratory artifacts. The accuracy of the method is analyzed by comparing FICA-extracted versus electrode-measured respiratory signals. It is concluded that, with this method, reliable results may be obtained for a wide array of magnetic recording scenarios.

Estimation of wavelet and short-time Fourier transform sonograms of normal and diabetic subjects’ electrogastrogram

Electrogastrography (EGG) is a noninvasive way to record gastric electrical activity of stomach muscle by placing electrodes on the abdominal skin. Our goal was to investigate the frequency of abnormalities of the EGG in real clinical diabetic gastroparesis patients using WT method and to compare performance of STFT and WT methods in the case of time–frequency resolution. The results showed that WT sonograms can be used to classify patients successfully as healthy or sick. And also, due to the fact that the WT method does not suffer from some intrinsic problems that affect the STFT method, one can see that the WT method can help improve the quality of the sonogram of the EGG signals.

Ellipsoidal electrogastrographic forward modelling

The theoretical and computational study of the electromagnetic forward and inverse problems in ellipsoidal geometry is important in electrogastrography because the geometry of the human stomach can be well approximated using this idealized body. Moreover, the anisotropies inherent to this organ can be highlighted by the characteristics of the electric potential associated with current dipoles in an ellipsoid. In this paper, we present a forward simulation for the stomach using an analytic expression of the gastric electric potential that employs a truncated expansion of ellipsoidal harmonics; we then demonstrate that an activation front of dipoles propagating along the body of an ellipsoid can simulate gastric electrical activity. In addition to the usefulness of our model, we also discuss its limitations and accuracy.

Estimating Gastric Rhythm Differences Using a Wavelet Method from the Electrogastrograms of Normal and Diabetic Subjects

Electrogastrogram (EGG) is the cutaneous recording of gastric electrical activity. Some patients with nausea, vomiting, early satiety, and patients with long term insulin‐dependent diabetes exhibit gastric electrical rhythm disturbances. We are interested in investigating the EGG to determine if abnormalities of the EGG occur in association with those gastric complaints. The aim of this document is to investigate long term diabetics with a history of such gastric dysrhythmia complaints in an effort to further characterize the frequency of abnormalities of the EGG in real clinical diabetic gastroparesis patients. For feature extraction purposes, we have performed Wavelet‐Packet analysis of EGG signals and have obtained power spectral density of wavelet‐packet details and approximation coefficients in diabetic patients suffering from gastric dysrhythmia (tachygastria, bradygastria) and healthy volunteers. Wavelet‐Packet analysis provides details of changes in frequency components at any time point, and enhanced interpretation of cutaneous EGG recordings. In conclusion, this paper has shown that the Wavelet‐Packet analysis method is very useful in the analysis of cutaneous EGG recordings, especially in detecting dysrhythmic events.

120 Effect of Unconjugated Bilirubin on Gastric Motility Intestinal Permeability (IP) and Fecal Calprotectin in Preterm Newborns

At present no data are available on the effects of unconjugated bilirubin (UCB) on the gut of the preterm. We evaluated 25 jaundiced preterm (12 male, GA 35.0±1.0 wks, BW 2152.2±301.3 g, serum bilirubin201.7millimol/L (range 97.4 - 265). Gastric electrical activity was recorded by cutaneous electrogastrography (EGG module UPS 2020 - MMS) for 30 minutes before and one hour after formula feed and the following parameters evaluated: gastric frequency and power, instability coefficient of frequency and power, percentage of normal slow wave, bradygastria and tachygastria. The urinary lactulose/mannitol ratio (La/Ma ratio) was measured after oral ingestion of a solution containing 8.6 g of lactulose and 140 mg of mannitol per 100 ml water at a dose of 2 ml/kg. Urine was then collected for five hours; lactulose and mannitol concentrations were measured by HPLC (high liquid phase chromatography) (mg/l) and La/Ma ratio calculated. Fecal calprotectin (FC) was measured by an ELISA kit (Calprest) and the stool samples were treated following the manufacturer s instructions. In the preprandial period, serum bilirubin correlates positively with the percentage of normal slow waves (r=0.60; p< 0.001) and negatively with percentage of tachygastria (r-0.42; p< 0.03). Correlations were lost in the postprandial period. A multiple linear regression model showed that intestinal permeability (La/Ma ratio) (mean 0.25 ± 0.15) is influenced by both UCB and FC (mean 319.8± 4.5) (r=051; p=0.03). These data show that UCB affects IP, gastric motility and gut inflammation. We believe that UCB represents a condition of increased risk for preterms due to a complex involvment of the whole intestinal apparatus that has never been hypothesised before.

Analysis of Canine Model of Gastric Electrical Uncoupling Using Recurrence Quantification Analysis

This study reports the results of recurrence quantification analysis (RQA) applied to internal gastric electrical activity (GEA) and cutaneous electrogastrographic (EGG) digital recordings obtained from acute canine models. The purpose of this chaos analysis is to differentiate three states--normal, mild, and severe induced electrical uncoupling--utilizing five quantities associated with RQA: percent recurrence, percent determinism, maximum deterministic line, entropy, and trend. The results indicate that percent recurrence and trend are the only quantities that relate the three states of gastric electrical uncoupling in any meaningful way. The ability of EGG to detect mild electrical uncoupling in the stomach appears to be limited due to the impact of numerous external factors on the signals, even if multichannel recordings are utilized.

Extraction of gastric slow waves from electrogastrograms: Combining independent component analysis and adaptive signal enhancement

The electrogastrogram (EGG), a cutaneous measurement of gastric electrical activity, is a mixture of gastric slow waves and noise. To detect the propagation of gastric slow waves, it is desired to obtain gastric slow waves in each of multichannel EGGs. Recently, independent component analysis (ICA) has shown its efficiency in separating the gastric slow wave from noisy multichannel EGGs. However, this method is not able to recover gastric slow waves in each of the multichannel EGGs. In this paper, a two-stage combined method was proposed for extracting gastric slow waves. First, ICA was performed to separate the gastric slow wave component from noisy multichannel EGGs. Second, adaptive signal enhancement with a reference input derived by the ICA in the first stage was employed to extract gastric slow waves in each channel. Quantitative analysis showed that, with the proposed method, the maximum root-mean-square error between the estimated time lag and its theoretical value in the simulations was only 0.65. The results from real EGG data demonstrated that the combined method was able to extract gastric slow waves from individual channels of EGGs which are important to identify the slow wave propagation. Therefore, the proposed method can be used to detect propagation of gastric slow waves from multichannel EGGs.

Evolution of Gastric Electrical Features and Gastric Emptying in Children with Duchenne and Becker Muscular Dystrophy

Although muscular dystrophy (MD) affects primarily striated muscles, smooth muscle cells of the gastrointestinal tract may also be involved. We recorded gastric electrical activity and gastric emptying time (GET) in children with MD at initial presentation and at 3-yr follow-up in order to detect gastric motor abnormalities and study their evolution along the clinical course. Twenty children with MD (median age: 4.6 yr; range age: 3-7 yr) were investigated by means of ultrasonography, for measuring GET, and by electrogastrography (EGG); 70 children served as controls. Ten patients had Duchenne muscular dystrophy (DMD) and 10 Becker muscular dystrophy (BMD). GET was significantly more delayed in MD patients (DMD, median: 195 min; range 150-260 min; BMD, median: 197 min; range: 150-250 min) than in controls (median: 150 min; 110-180 min; p < 0.05); it markedly worsened at the follow-up in DMD (median: 270 min; range 170-310 min; p < 0.001 vs controls) but not in BMD patients (median: 205 min; 155-275 min; p < 0.05 vs DMD). Baseline EGG showed a significantly lower prevalence of normal rhythm and significantly higher prevalence of dysrhythmias in both groups of patients as compared to controls (% of normal rhythm: DMD 66.7 +/- 8.2, BMB 67.2 +/- 11.5, controls 85.3 +/- 7.2, p < 0.001; % of tachygastria: DMD 28.4 +/- 8.0, BMB 29.8 +/- 12.3, controls 10.6 +/- 5.1, p < 0.001; % of dominant frequency instability coefficient: DMD 36.1 +/- 6.0, BMB 33.2 +/- 2.9, controls 17.9 +/- 7.1, p < 0.001); furthermore, no difference in fed-to-fasting ratio of the dominant EGG power was found between the two groups and controls (DMD 2.84 +/- 1.27, BMB 2.82 +/- 0.98, controls 3.04 +/- 0.85, ns). However, at the follow-up no significant change in the prevalence of normal rhythm and dysrhythmias occurred in both groups (ns vs baseline values), whereas only DMD patients showed a marked reduction in fed-to-fasting power ratio (0.78 +/- 0.59; p < 0.001 vs controls and BMD; p < 0.05 vs baseline), which correlated with the progressive neuromuscular weakness occurring in DMD subjects (r, 0.75; p < 0.001). In children with MD, there is an early abnormality in gastric motility that is due to deranged regulatory mechanisms, whereas contractile activity of smooth muscle cells seems to be preserved. At the follow-up, DMD patients exhibited a progressive failure in neuromuscular function, which was accompanied by a gastric motility derangement with worsening in GET and in EGG features suggesting an altered function of gastric smooth muscle cells.