Enhanced electrogastrography: A realistic way to salvage a promise that was never kept?

AIM: To enhance the clinical utility of electrogastrography (EGG), which has been recorded since 1922, but is clinically unutilized. METHODS: An innovative method to salvage the promise of EGG is proposed by introducing a preliminary procedure, while maintaining the electrodes, standardized equipment, and signal processing utilized in the well-established EGG testing of today. The proposed enhanced EGG (EEGG) protocol involves swallowing an ingestible capsule containing miniature electronic oscillator embedded in an expandable, self-disintegratable, biocompatible pseudobesoar residing in the stomach for the duration of the test. The benefits of the proposed approach are outlined, tested and discussed in details. RESULTS: Experiments were performed on eight mongrel dogs (6F, 4M, 23.8 ± 3.3 kg). Four were administered an active EEGG capsule, while the rest were given a deactivated (battery removed) capsule. Pharmacologically facilitated gastric motility revealed a significant (P < 0.01) Pearson correlation between gastric motility indices obtained by force transducers implanted directly on the stomach, and the motility indices obtained by EEGG. A particular emphasis was made on preserving standard EGG-related hardware and software in order to facilitate the introduction of the proposed EEGG in environments which already utilize standard EGG testing. The expanded intragastric pseudobezoar containing the miniature electronic oscillator was retained during the tests, and could be disintegrated on demand. CONCLUSION: Enhancing standard EGG by an ingestible, self-expanding and self-disintegrating pseudobesoar containing a miniature electronic oscillator can be an important avenue for clinical applicability of this test.

Wearable Microsystem for Minimally Invasive, Pseudo-Continuous Blood Glucose Monitoring: The e-Mosquito.

This paper presents a wearable microsystem for minimally invasive, autonomous, and pseudo-continuous blood glucose monitoring, addressing a growing demand for replacing tedious fingerpricking tests for diabetic patients. Unlike prevalent solutions which estimate blood glucose levels from interstitial fluids or tears, our design extracts a whole blood sample from a small lanced skin wound using a novel shape memory alloy (SMA)-based microactuator and directly measures the blood glucose level from the sample. In vitro characterization determined that the SMA microactuator produced penetration force of 225 gf, penetration depth of 3.55 mm, and consumed approximately 5.56 mW·h for triggering. The microactuation mechanism was also evaluated by extracting blood samples from the wrist of four human volunteers. A total of 19 out of 23 actuations successfully reached capillary vessels below the wrists producing blood droplets on the surface of the skin. The integrated potentiostat-based glucose sensing circuit of our e-Mosquito device also showed a good linear correlation (R2 = 0.9733) with measurements using standard blood glucose monitoring technology. These proof-of-concept studies demonstrate the feasibility of the e-Mosquito microsystem for autonomous intermittent blood glucose monitoring.

Catheter-based acoustic interrogation device for real-time monitoring of the dynamics of the lower esophageal sphincter: in vitro and pilot canine studies.

This paper presents a novel minimally-invasive catheter-based acoustic interrogation device for real-time monitoring the dynamics of the lower esophageal sphincter (LES). Dysfunction of the LES could result gastrointestinal (GI) diseases, such as gastroesophageal reflux disease (GERD). A micro-oscillator actively emitting sound wave at 16 kHz is located at one side of the LES, and a miniature microphone is located at the other side of the LES to capture the sound generated from the oscillator. Thus, the dynamics of the opening and closing of the LES can be monitored. The device was tested in vitro by utilizing a custom-designed LES simulator, as well as in vivo in a pilot canine model. In the in vitro test, the sound was captured by the microphone and its strength was correlated with the level of LES opening and closing which was controlled by the simulator. The measurements showed statistically significant (p < 0.05) Pearson correlation coefficients (0.905 on the average in quiet environment and 0.736 on the average in noisy environment, DOF = 9). In the in vivo test, the LES was forced open and closed by a transoral endoscope, which was monitored in real-time by a transpyloric endoscope inserted from the duodenum and positioned into the distal stomach. Frame-by-frame video analysis validated the interrelation between the sound strength and the LES opening and closing. The LES dynamics monitored by the proposed device has the potential to become a valuable minimally-invasive technique for understanding LES dysfunction.

A catheter-based acoustic interrogation device for monitoring motility dynamics of the lower esophageal sphincter.

This paper presents novel minimally-invasive, catheter-based acoustic interrogation device for monitoring motility dynamics of the lower esophageal sphincter (LES). A micro-oscillator actively emitting sound wave at 16 kHz is located at one side of the LES, and a miniature microphone is located at the other side of the sphincter to capture the sound generated from the oscillator. Thus, the dynamics of the opening and closing of the LES can be quantitatively assessed. In this paper, experiments are conducted utilizing an LES motility dynamics simulator. The sound strength is captured by the microphone and is correlated to the level of LES opening and closing controlled by the simulator. Measurements from the simulator model show statistically significant (p < 0.05) Pearson correlation coefficients (0.905 on the average in quiet environment and 0.736 on the average in noisy environment, D.O.F. = 9). Measuring the level of LES opening and closing has the potential to become a valuable diagnostic technique for understanding LES dysfunction and the disorders associated with it.

Transcutaneous intraluminal impedance measurement for minimally invasive monitoring of gastric motility: validation in acute canine models.

Transcutaneous intraluminal impedance measurement (TIIM) is a new method to cutaneously measure gastric contractions by assessing the attenuation dynamics of a small oscillating voltage emitted by a battery-powered ingestible capsule retained in the stomach. In the present study, we investigated whether TIIM can reliably assess gastric motility in acute canine models. Methods. Eight mongrel dogs were randomly divided into 2 groups: half received an active TIIM pill and half received an identically sized sham capsule. After 24-hour fasting and transoral administration of the pill (active or sham), two force transducers (FT) were sutured onto the antral serosa at laparotomy. After closure, three standard cutaneous electrodes were placed on the abdomen, registering the transluminally emitted voltage. Thirty-minute baseline recordings were followed by pharmacological induction of gastric contractions using neostigmine IV and another 30-minute recording. Normalized one-minute baseline and post-neostigmine gastric motility indices (GMIs) were calculated and Pearson correlation coefficients (PCCs) between cutaneous and FT GMIs were obtained. Statistically significant GMI PCCs were seen in both baseline and post-neostigmine states. There were no significant GMI PCCs in the sham capsule test. Further chronic animal studies of this novel long-term gastric motility measurement technique are needed before testing it on humans.

Gastric electrical stimulation for the treatment of obesity: from entrainment to bezoars-a functional review.

GROWING WORLDWIDE OBESITY EPIDEMIC HAS PROMPTED THE DEVELOPMENT OF TWO MAIN TREATMENT STREAMS: (a) conservative approaches and (b) invasive techniques. However, only invasive surgical methods have delivered significant and sustainable benefits. Therefore, contemporary research exploration has focused on the development of minimally invasive gastric manipulation methods featuring a safe but reliable and long-term sustainable weight loss effect similar to the one delivered by bariatric surgeries. This antiobesity approach is based on placing external devices in the stomach ranging from electrodes for gastric electrical stimulation to temporary intraluminal bezoars for gastric volume displacement for a predetermined amount of time. The present paper examines the evolution of these techniques from invasively implantable units to completely noninvasive patient-controllable implements, from a functional, rather than from the traditional, parametric point of view. Comparative discussion over the available pilot and clinical studies related to gastric electrical stimulation outlines the promises and the fallacies of this concept as a reliable alternative anti-obesity strategy.

Suture marker lesion detection in the colon by self-stabilizing and unmodified capsule endoscopes: pilot study in acute canine models.

BACKGROUND: Capsule endoscopy is a noninvasive method for examining the small intestine. Recently, this method has been used to visualize the colon. However, the capsule often tumbles in the wider colon lumen, resulting in potentially missed pathology. In addition, the capsule does not have the ability to distend collapsed segments of the organ. Self-stabilizing capsule endoscopy is a new method of visualizing the colon without tumbling and with the ability to passively distend colon walls. OBJECTIVE: To quantitatively compare the detection rate of intraluminal suture marker lesions for colonoscopy by using a custom-modified, self-stabilizing capsule endoscope (SCE); an unmodified capsule endoscope (CE) of the same brand; and a standard colonoscope. DESIGN: Four mongrel dogs underwent laparotomy and the implantation of 5 to 8 suture markers to approximate colon lesions. Each dog had both capsule endoscopy and self-stabilizing capsule endoscopy, administered consecutively in random order. In each case, the capsule was inserted endoscopically into the proximal lumen of the colon followed by pharmacologically induced colon peristalsis to propel it distally through the colon. Blinded standard colonoscopy was performed by an experienced gastroenterologist after the capsule endoscopies. SETTING: Experimental study in a live canine model. SUBJECTS: Four dogs. INTERVENTION: Laparotomy, capsule endoscopy, colonoscopy. MAIN OUTCOME MEASUREMENTS: Comparison of the marker detection rate of the SCE to that of the unmodified MiroCam CE and a colonoscope. RESULTS: The average percentages of the marker detection rate for unmodified capsule endoscopy, self-stabilizing capsule endoscopy, and colonoscopy, respectively, were 31.1%, 86%, and 100% (P < .01), with both self-stabilizing capsule endoscopy and colonoscopy performing significantly better than the unmodified capsule endoscopy. LIMITATIONS: Acute canine model, suture markings poorly representative of epithelial polyps, limited number of animals. CONCLUSION: The proposed self-stabilizing capsule endoscope delivered a significant improvement in detection rates of colon suture markings when compared with the unmodified capsule endoscope.

Colometer: a real-time quality feedback system for screening colonoscopy.

AIM: To investigate the performance of a new software-based colonoscopy quality assessment system. METHODS: The software-based system employs a novel image processing algorithm which detects the levels of image clarity, withdrawal velocity, and level of the bowel preparation in a real-time fashion from live video signal. Threshold levels of image blurriness and the withdrawal velocity below which the visualization could be considered adequate have initially been determined arbitrarily by review of sample colonoscopy videos by two experienced endoscopists. Subsequently, an overall colonoscopy quality rating was computed based on the percentage of the withdrawal time with adequate visualization (scored 1-5; 1, when the percentage was 1%-20%; 2, when the percentage was 21%-40%, etc.). In order to test the proposed velocity and blurriness thresholds, screening colonoscopy withdrawal videos from a specialized ambulatory colon cancer screening center were collected, automatically processed and rated. Quality ratings on the withdrawal were compared to the insertion in the same patients. Then, 3 experienced endoscopists reviewed the collected videos in a blinded fashion and rated the overall quality of each withdrawal (scored 1-5; 1, poor; 3, average; 5, excellent) based on 3 major aspects: image quality, colon preparation, and withdrawal velocity. The automated quality ratings were compared to the averaged endoscopist quality ratings using Spearman correlation coefficient. RESULTS: Fourteen screening colonoscopies were assessed. Adenomatous polyps were detected in 4/14 (29%) of the collected colonoscopy video samples. As a proof of concept, the Colometer software rated colonoscope withdrawal as having better visualization than the insertion in the 10 videos which did not have any polyps (average percent time with adequate visualization: 79% ± 5% for withdrawal and 50% ± 14% for insertion, P < 0.01). Withdrawal times during which no polyps were removed ranged from 4-12 min. The median quality rating from the automated system and the reviewers was 3.45 [interquartile range (IQR), 3.1-3.68] and 3.00 (IQR, 2.33-3.67) respectively for all colonoscopy video samples. The automated rating revealed a strong correlation with the reviewer's rating (ρ coefficient= 0.65, P = 0.01). There was good correlation of the automated overall quality rating and the mean endoscopist withdrawal speed rating (Spearman r coefficient= 0.59, P = 0.03). There was no correlation of automated overall quality rating with mean endoscopists image quality rating (Spearman r coefficient= 0.41, P = 0.15). CONCLUSION: The results from a novel automated real-time colonoscopy quality feedback system strongly agreed with the endoscopists' quality assessments. Further study is required to validate this approach.

Technical note: Evaluation of tined endoscopically placed mucosal leads for temporary gastric neurostimulation.

OBJECTIVE: To compare larger diameter corkscrew-tined leads with previously described intracardiac pacing leads for temporary gastric neurostimulation in a canine model. MATERIALS AND METHODS: Two mongrel dogs underwent gastroscopy under general anesthesia, with endoscopic placement of two cardiac leads (1 mm tine diameter, 4 mm depth) placed sequentially in 1) transverse configuration in the distal antrum mucosa; 2) longitudinal (1 cm apart) configuration in gastric corpus. Stomach was then stimulated with maximal parameters to induce neutrally mediated contraction. Procedures were then repeated with larger leads (5 mm tine diameter, 8 mm length). Gastric contractions were measured with serosal strain transducers. RESULTS: Leads were placed endoscopically without difficulty. Neither lead type punctured through to the serosa of the stomach. Neither cardiac nor larger leads were capable of eliciting any gastric contractile activity with endoscopic placement either in the transverse or longitudinal orientations. DISCUSSION: While successful on the serosal side, both the cardiac leads and the larger alternative leads failed to produce stomach contraction when implanted mucosally. This may be due to the elastic nature of the mucosa, which was observed to twist around both types of leads significantly, hindering proper penetration into the muscularis. CONCLUSION: These results suggest that the current concept of temporary gastric electrical neurostimulation via a mucosal approach must be reevaluated, as the procedure most likely does not accurately mimic electrical stimulation in the muscularis.

Self-stabilizing colonic capsule endoscopy: pilot study of acute canine models.

Video capsule endoscopy (VCE) is a noninvasive method for examining the gastrointestinal tract which has been successful in small intestine studies. Recently, VCE has been attempted in the colon. However, the capsule often tumbles in the wider colonic lumen, resulting in missed regions. Self-stabilizing VCE is a novel method to visualize the colon without tumbling. The aim of the present study was to comparatively quantify the effect of stabilization of a commercially available nonmodified capsule endoscope (CE) MiroCam and its modified self-stabilizing version in acute canine experiments. Two customized MiroCam CEs were reduced in volume at the nonimaging back-end to allow the attachment of a self-expanding, biocompatible stabilizing device. Four mongrel dogs underwent laparotomy and exteriorization of a 15-cm segment of the proximal descending colon. A single CE, either self-stabilizing or nonmodified was inserted through an incision into the lumen of the colon followed by pharmacologically induced colonic peristalsis. The inserted capsule was propelled distally through the colon and expelled naturally through the anus. Novel signal processing method was developed to quantify the video stabilization based on camera tracking a predetermined target point (locale). The average locale trajectory, the average radius movement of the locale, and the maximum rate of change of the locale for sequential images were significantly lower for the stabilized capsules compared to the nonstabilized ones . The feasibility of self-stabilized capsule endoscopy has been demonstrated in acute canine experiments.

Pilot study of longitudinal ultrasonic sensor for dynamic volumetric assessment of gastroesophageal reflux.

In patients with gastroesophageal reflux disease (GERD), esophageal symptoms are traditionally diagnosed by monitoring the contact time between the reflux content and the esophagus using multichannel intraluminal impedance and pH (MII-pH) catheters. However, esophageal catheter for quantifying the volume of reflux content is still lacking. The present work proposes an innovative method to develop a longitudinal ultrasonic catheter and an information extraction system for reflux event detection and reflux volume estimation. Gastroesophageal model that mimics reflux events was developed to test the proposed catheter. Ultrasonic sensing was evaluated by simulating different volumes of reflux. The obtained signals showed good consistency in detecting reflux events and measuring reflux volume. During an in vivo human testing, a MII-pH catheter was used simultaneously to compare the ultrasonic output. Both in vitro and in vivo human testing results demonstrated the feasibility of utilizing the proposed method for gastroesophageal reflux (GER) detection and reflux volume estimation.

Pilot study of temporary controllable gastric pseudobezoars for dynamic non-invasive gastric volume reduction.

Invasive surgical procedures for gastric volume reduction or bypass have been considered the most effective approach to sustainable long-term weight reduction. However, non-invasive techniques for dynamic volume reduction from inside the stomach are lacking. The aim of this study was to propose temporary, permeable, controllable pseudobezoars for non-invasive, long-term sustainable gastric volume reduction and to test them in pilot human studies. Permeable sac-like carriers made from biocompatible and biodegradable material were filled with expandable superabsorbent fiber and polymer granules. The implements were designed to prevent the expulsion of the pseudobezoars through the pylorus for a controlled time period. The pseudobezoars were administered transorally to two human patients (2M, 78.9 kg/174 cm, girth 88.1 cm, and 89.7 kg/175, girth 95.2 cm). Body weight dynamics, girth, level of satiety, stools, bowel regularity and notable side effects were monitored in three distinct 1 month periods: baseline, therapy and washout. Sonographic verification of the presence of pseudobezoars in the stomachs of both subjects was performed at the end of the therapy month and was repeated at the end of the washout period to examine the clearance of the implements. During the therapy month, both individuals exhibited significant weight and girth reduction (p < 0.05), and substantially increased satiety levels. The patients retained their bowel regularity and did not report any notable side effects. The temporary pseudobezoars were clearly noticeable sonographically in both patients at the end of the therapy month and cleared after its discontinuation. Controllable temporary pseudobezoars were designed and tested in pilot studies.

Use of multichannel electrogastrography for noninvasive assessment of gastric myoelectrical activity in dogs.

OBJECTIVE: To evaluate whether changes in gastric myoelectrical activity in healthy, awake dogs can be detected via multichannel electrogastrography (EGG). ANIMALS: 6 healthy hound-breed dogs. PROCEDURES: For each dog, 8-channel EGG was performed after food had been withheld for 12 hours and at 30 minutes after subsequent feeding; 60 minutes after feeding, atropine (0.04 mg/kg) was administered IM to induce ileus, and 30 minutes later, EGG was again performed. Mean cycles per minute (cpm) values of the dominant frequency (a measure of the rhythmicity of gastric electrical activity) and mean power ratios (ie, power measured after treatment divided by the power measured when food was withheld) were calculated. Motility of the gastric antrum was assessed via B-mode ultrasonography during the same phases; contractions determined ultrasonographically were correlated with EGG power for each channel in each phase. RESULTS: The criterion for stability (SD of the dominant frequency < 15% of the cpm value in at least 3 of the 8 EGG channels) was met in 4 of the 6 dogs (only in long-distance channels). The mean power ratios were significantly higher in the postprandial phase than in the ileus phase. Compared with the postprandial phase, significantly fewer contractions per minute were evident ultrasonographically in the ileus and food-withholding phases. There was a significant and good correlation between EGG power and ultrasonographic findings in all 8 channels. CONCLUSIONS AND CLINICAL RELEVANCE: Electrogastrography may be useful in assessing gastric myoelectrical activities in awake dogs with naturally occurring gastrointestinal disease, including gastric dilatation-volvulus.

Effect of electrical stimulation of the LES on LES pressure in a canine model.

Gastric electrical stimulation modulates lower esophageal sphincter pressure (LESP). High-frequency neural stimulation (NES) can induce gut smooth muscle contractions. To determine whether lower esophageal sphincter (LES) electrical stimulation (ES) can affect LESP, bipolar electrodes were implanted in the LES of four dogs. Esophageal manometry during sham or ES was performed randomly on separate days. Four stimuli were used: 1) low-frequency: 350-ms pulses at 6 cycles/min; 2) high-frequency-1: 1-ms pulses at 50 Hz; 3) high-frequency-2: 1-ms pulses at 20 Hz; and 4) NES: 20-ms bipolar pulses at 50 Hz. Recordings were obtained postprandially. Tests consisted of three 20-min periods: baseline, stimulation/sham, and poststimulation. The effect of NES was tested under anesthesia and following IV administration of l-NAME and atropine. Area under the curve (AUC) and LESP were compared among the three periods, by ANOVA and t-test, P < 0.05. Data are shown as means +/- SD. We found that low-frequency stimulation caused a sustained increase in LESP: 32.1 +/- 12.9 (prestimulation) vs. 43.2 +/- 18.0 (stimulation) vs. 50.1 +/- 23.8 (poststimulation), P < 0.05. AUC significantly increased during and after stimulation. There were no significant changes with other types of ES. With NES, LESP initially rose and then decreased below baseline (LES relaxation). During NES, N(G)-nitro-l-arginine methyl ester increased both resting LESP and the initial rise in LESP and markedly diminished the relaxation. Atropine lowered resting LESP and abolished the initial rise in LESP. In conclusion, low frequency ES of the LES increases LESP in conscious dogs. NES has dual effect on LESP: an initial stimulation, cholinergically mediated, followed by relaxation mediated by nitric oxide.

Use of multichannel electrointestinography for noninvasive assessment of myoelectrical activity in the cecum and large colon of horses.

OBJECTIVE: To evaluate whether changes in myoelectrical activity in the cecum and large colon of horses can be detected via multichannel electrointestinography (EIG). ANIMALS: 6 healthy mature horses. PROCEDURES: Each horse underwent 3 EIG procedures. Intestinal myoelectrical activity (cecum and large colon) was recorded during a 20-minute period following i.v. administration of physiologic saline (0.9% NaCl) solution (20 mL; baseline), erythromycin lactobionate (0.5 mg/kg), or detomidine (0.015 mg/kg); intestinal contractions were concurrently viewed via B-mode ultrasonography. By use of computer software, 8-channel EIG recordings were analyzed and the mean of the dominant frequency (a measure of the rhythmicity of gastric electrical activity) expressed in cycles per minute (cpm) was obtained. Total power (muV(2)) was calculated, and treatment effect was expressed as the power ratio (ie, treatment-associated power divided by the baseline power). RESULTS: The dominant frequency cpm values were not stable, and no significant differences between treatments were detected. Compared with the effects of saline solution treatment, detomidine significantly reduced the mean cecal and colonic power ratios. Erythromycin significantly reduced the cecal power ratio and increased the colonic power ratio, although the increase was significant in only 1 channel. Ultrasonographic findings and total power (predominantly from the long-distance electrode pairs) were significantly correlated. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, EIG was useful for assessment of changes in myoelectrical activity in the cecum and large colon. Multiple electrodes should be used to cover a larger area of the intestine, and agreement between multiple channels is needed to make the analysis meaningful.

Diamagnetically-stabilized levitation control of an intraluminal magnetic capsule.

Controlled navigation promotes full utilization of capsule endoscopy for reliable real-time diagnosis in the gastrointestinal (GI) tract, but intermittent natural peristalsis can disturb the navigational control, destabilize the capsule and take it out of levitation. A real-size magnetic navigation system that can handle peristaltic forces of up to 1.5 N was designed utilizing the computer-aided design (CAD) system Maxwell 3D (Ansoft, Pittsburg, PA), and was verified using a small-size physical experimental setup. The proposed system contains a pair of 50-cm in diameter, 10,000-turns copper electromagnets with a 10-cm by 10-cm ferrous core driven by currents of up to 300 Amperes and can successfully maintain position control over the levitating capsule during peristalsis. The addition of Bismuth diamagnetic casing for stabilizing the levitating capsule was also studied.

Feedback control of retrograde peristalsis using Neural Gastric Electrical Stimulation.

Neural Gastric Electrical Stimulation (NGES) is a new method for invoking gastric contractions under microprocessor control. However, optimization of this technique using feedback mechanisms to minimize power consumption and maximize effectiveness has been lacking. The present work proposes a prototype feedback-controlled neural gastric electrical stimulator for the treatment of obesity. Both a force-based and an interelectrode impedance-based feedback neurostimulator were implemented and tested. Four mongrel dogs (2 M, 2 F, weight 14.9 ++/- 2.3kg) underwent subserosal implantation of 2-channel 1-cm bipolar electrode leads in the distal antrum. Two of the dogs were stimulated with a force-based feedback system and the other two animals were stimulated utilizing an interelectrode impedance-based feedback system. Both feedback systems were able to recognize Erythromycin-driven contractions of the stomach and were capable of overriding them with NGES-invoked retrograde contractions. The proposed technique could be helpful for retaining food longer in the stomach, thus inducing early satiety and diminishing food intake.

Ingestible capsule for impedance and pH monitoring in the esophagus.

Twenty-four-hour ambulatory pH monitoring is an essential tool for diagnosing gastroesophageal reflux disease (GERD). Simultaneous impedance and pH monitoring of the esophagus improves the detection and characterization of GERD. Conventional catheter-based monitoring systems are uncomfortable and interfere with the normal activity of the patient. To overcome these disadvantages, different wireless esophageal monitoring systems have been proposed. A capsule containing sensors for impedance and pH monitoring with wireless communication capabilities is presented. A low cost miniature microcontroller was utilized for interfacing between the sensors and a wireless transmitter. The microcontroller program allowed efficient management of the electric power provided by a 3-V battery. Magnetic holding is proposed as an alternative to surgical affixation of the monitoring capsule. Permanent neodymium magnets separated by 27 cm successfully held the capsule in a test tube. Experimental results demonstrated that friction force can aid magnetic holding to overcome peristalsis. The proposed design efficiently detected acid and nonacid reflux. More research regarding the holding method and capsule packaging are necessary to optimize the mechanical performance of the proposed design in order to facilitate clinical testing on human subjects.

Parametric study of neural gastric electrical stimulation in acute canine models.

Manipulation of gastric motility by gastric electrical stimulation (GES) has been suggested as a minimally invasive alternative treatment of gastric motility disorders and obesity. However, only neural GES (NGES) has been successful in invoking gastric contractions. Nevertheless, the relationship between these contractions and the controlling NGES parameters has not been quantified. We aimed at determining the relationship between the electrical energy delivered to the tissue as a function of NGES parameters, and the strength and duration of the resulting invoked gastric contractions. Five healthy mongrel dogs underwent subserosal prepyloric implantation of two NGES electrode pairs. Gastric motility was captured by a force transducer implanted in the vicinity of the distal pair of stimulating electrodes. Custom-designed implantable stimulator delivered NGES with 8-16 V (peak-to-peak) amplitudes, and 60-100% duty cycles. Normalized motility index (MI) was utilized to quantify the contractions recorded from the force transducer. The MI increased with increasing voltage amplitudes. However, it remained remarkably constant across all duty cycles when voltage was held constant. Calculated motility generation efficiency indices (MGEI) indicated that highest energy efficiency for invoked motility was achieved at the lowest duty cycle. The parametric data obtained in the present study can be utilized to optimize the power efficiency of implantable gastric neurostimulators.

Implantable neural electrical stimulator for external control of gastrointestinal motility.

Functional electrical stimulation has been suggested as a possible avenue for treating a variety of gastrointestinal motility-related disorders such as gastroparesis, chronic constipation and morbid obesity. The aims of the present study were to design a radio-frequency controlled multi-channel implantable neural gastrointestinal electrical stimulator and test it in an acute canine model. The stimulation parameters can be reprogrammed after implantation, allowing the execution of parametric studies and the investigation of their efficacy in producing controlled gastrointestinal contractions. Bipolar pulse trains of 50Hz frequency, 8-16V(pp) amplitude, 10-100% duty cycle, 1-120s duration, and 2s to 1h pause between successive stimulation sessions were delivered to the stomachs of nine dogs. The resulting contractions were measured by force transducers and digitally recorded on a personal computer. The acute studies confirmed the effectiveness of electrical stimulation in producing invoked gastric contractile activity under the control of the implantable neurostimulator.