James Whiting

Kinetics of transient hiatus hernia during transient lower esophageal sphincter relaxations and swallows in healthy subjects

Background  Proximal displacement of the gastro‐esophageal junction (GEJ) is present in hiatus hernia but also occurs transiently during transient lower esophageal sphincter relaxations (TLESRs) and swallows. Using a novel magnetic‐based technique we have performed detailed examination of the GEJ movement during TLESRs and swallows in healthy subjects.

Waist belt and central obesity cause partial hiatus hernia and short-segment acid reflux in asymptomatic volunteers

Objective There is a high incidence of inflammation and metaplasia at the gastro-oesophageal junction (GOJ) in asymptomatic volunteers. Additionally, the majority of patients with GOJ adenocarcinomas have no history of reflux symptoms. We report the effects of waist belt and increased waist circumference (WC) on the physiology of the GOJ in asymptomatic volunteers. Design 12 subjects with normal and 12 with increased WC, matched for age and gender were examined fasted and following a meal and with waist belts on and off. A magnet was clipped to the squamo-columnar junction (SCJ). Combined assembly of magnet-locator probe, 12-channel pH catheter and 36-channel manometer was passed. Results The waist belt and increased WC were each associated with proximal displacement of SCJ within the diaphragmatic hiatus (relative to upper border of lower oesophageal sphincter (LOS), peak LOS pressure point and pressure inversion point, and PIP (all p<0.05). The magnitude of proximal migration of SCJ during transient LOS relaxations was reduced by 1.6–2.6 cm with belt on versus off (p=0.01) and in obese versus non-obese (p=0.04), consistent with its resting position being already proximally displaced. The waist belt, but not increased WC, was associated with increased LOS pressure (vs intragastric pressure) and movement of pH transition point closer to SCJ. At 5 cm above upper border LOS, the mean % time pH <4 was <4% in all studied groups. Acid exposure 0.5–1.5 cm above SCJ was increased, with versus without, belt (p=0.02) and was most marked in obese subjects with belt. Conclusions Our findings indicate that in asymptomatic volunteers, waist belt and central obesity cause partial hiatus herniation and short-segment acid reflux. This provides a plausible explanation for the high incidence of inflammation and metaplasia and occurrence of neoplasia at the GOJ in subjects without a history of reflux symptoms.

Measuring movement and location of the gastroesophageal junction: research and clinical implications

Abstract Understanding the physiology of gastroesophageal junction (GEJ) is important as failure of its function is associated with reflux disease, hiatus hernia, and cancer. In recent years, there have been impressive developments in high resolution technologies allowing measurement of luminal pressure, pH, and impedance. One obvious deficiency is the lack of technique to monitor the movement and location of the GEJ over a prolonged period of time. Proximal movement of the GEJ during peristalsis and transient lower esophageal sphincter relaxations (TLESRs) is due to shortening of the longitudinal muscle of the esophagus. Techniques for measuring shortening include fluoroscopic imaging of mucosal clip, high-frequency intraluminal ultrasound, and high resolution manometry, but these techniques have limitations. Short segment reflux is recently found to be more common than traditional reflux and may account for the high prevalence of intestinal metaplasia and cancer seen at GEJ. While high resolution pHmetry is available, there is no technique that can reliably and continuously measure the position of the squamocolumnar junction. A new technique is recently reported allowing a precise and continuous measurement of the GEJ based on the principle of Hall effect. Reported studies have validated its accuracy both on the bench and against the gold standard, fluoroscopy. It has been used alongside high resolution manometry in studying the behavior of the GEJ during TLESRs and swallows. While there are challenges associated with this new technique, there are promising ongoing developments. There is exciting time ahead in research and clinical applications for this new technique.

Development and validation of a probe allowing accurate and continuous monitoring of location of squamo-columnar junction

INTRODUCTION Most pathology of the upper gastrointestinal tract now occurs close to the gastro-oesophageal squamo-columnar junction (SCJ). Studying the pathophysiology of this region even using high resolution pH, impedance and manometry is unreliable due to constant movement with respiration, swallowing and transient lower oesophageal sphincter relaxations. AIMS AND METHODS A technique is reported allowing continuous real-time monitoring of the position of the SCJ. It involves endoscopically clipping a magnet (2 mm × 1 mm) to the SCJ and monitoring its position relative to a probe in the oesophago-gastric lumen. The latter has 26 Hall-Effect sensors mounted at 5mm spacing on a circuit board within a silicone tube. RESULTS Bench studies: The recorded position of the magnet along the length of the probe was compared with its actual position. Accuracy was related to the distance between magnet and probe, orientation of the magnet relative to the probe and whether the magnet was anterior, posterior or lateral to the probe. Including all possible orientations of the magnet at or nearer than 10mm from the probe, the median accuracy along the length of probe was 2.4 mm (IQR 2.1 mm). The proportion of all possible orientations within 10mm of the probe giving an accuracy of ±10 mm was 88.9%. In vivo studies: With simultaneous fluoroscopy, eight healthy subjects were asked to perform normal breathing, deep breathing, water swallows and finally advancement and retraction of probe over a 12 cm segment. The position recorded by fluoroscopy and probe at each second interval were compared. The correlation co-efficient for all 224 position readings was 0.96 (95% CI: 0.89-0.96). No significant interference was observed when the probe was tested alongside high resolution pH and manometry. CONCLUSION Used in conjunction with high resolution pH, impedance and manometry, this technique will allow for the first time detailed studies at the squamo-columnar junction.

PTU-138 Central Obesity and Waist Belt Cause Partial Hiatus Hernia and Short Segment Acid Reflux in Healthy Volunteers

Introduction Epidemiology demonstrates an association between obesity, hiatus hernia and acid reflux but mechanism is unclear. We have examined the structure and function of the gastro-oesophageal (GO) junction in healthy subjects with and without obesity and the effects of elevating intra-abdominal pressure with belt. Methods We recruited 8 subjects with normal ( < 94 cm males < 80 cm females) and 8 with increased ( > 102 cm males > 88 cm females) waist circumference, matched for age and gender. To allow accurate monitoring of location of the GO junction and its proximal movement during TLOSRs, a magnet (2x1 mm) was endoscopically clipped to the SCJ. Combined assembly of locator probe, high-resolution pH catheter and slimline manometer was passed nasally. After a standard meal, recording seated upright was continued for an hour. A waist belt was applied on a separate day throughout the entire recording. The effect of obesity was assessed by comparing obese vs. non-obese, both without belt. The effect of belt was assessed by comparing entire group with and without belt. The effect of belt in obesity was assessed by comparing belt-on vs. off in obese subjects. All results were in mean (SEM). Results Location of the SCJ (P = 0.006) and pH step-down (P = 0.01) were displaced proximally in obese vs. non-obese but the diaphragm was not displaced as reflected by peak LOS pressure (pLOS) and pressure inversion point (PIP) (Figure). With belt-on vs. off, there was similarly proximal displacement of SCJ and pH step-down and also of the diaphragm (P = 0.003) and LOS (upper and lower border, P = 0.01 and 0.03 respectively). In obese subjects with belt-on vs. off, there was proximal displacement of SCJ, pH step-down and diaphragm. There was marked proximal migration of SCJ during TLOSRs with its magnitude being less in obese vs. non-obese (4.2 vs. 6.8 cm, P = 0.04) and belt-on vs. off (3.9 vs. 5.5 cm, P = 0.01), consistent with its resting position being already proximally displaced. At traditional site (5 cm above LOS), the mean % time pH < 4 was minimal (0 – 0.5%) in all studied groups, however, acid exposure above the SCJ but below upper border LOS was increased in belt-on vs. off (6.2% vs. 1.6%, P = 0.01) and in obesity with belt-on vs. off (9.7% vs. 3.0%, P = 0.04) but not obese vs. non-obese (P = 0.2). Abstract PTU-138 Figure Conclusion Our findings indicate that in asymptomatic volunteers, central obesity and waist belt cause partial hiatus herniation and that waist belt also causes short segment reflux. Disclosure of Interest None Declared

Towards minimally invasive monitoring for gastroenterology -An external Squamocolumnar Junction Locator

Transient lower oesophageal sphincter relaxations (TLOSRs) occur frequently and are the main mechanism of acid reflux. The only means of currently detecting TLOSRs is intra-luminal manometry and the probes themselves may stimulate TLOSRs. The squamo-columnar junction moves 4-5 centimeters proximally during TLOSRs and this provides a means of detecting such episodes. The objective of this work is to develop a sensor system capable of detecting the movement of a miniature magnet attached to the squamo-columnar junction from outside the body and thus allow detection of TLOSRs without the artifact associated with intraluminal detection probes. A GaAs Hall effect sensor was selected and an alternating current supply was developed with a combination of filters and a Phase Sensitive Detector, to detect the magnet. The oscillation frequency of the current was chosen in order to reduce electronic noise, and filtering outside this frequency means the signal to noise ratio was greatly improved. The phase sensitive detector was employed to accurately convert the amplitude of the sensors output to a DC signal. With the addition of paired Flux Concentrators increases the range up to 10.2 centimetres, an improvement of 580% over commercial Hall effect sensors. The AC circuit and flux concentrator device far exceeds the sensitivity of the current Hall effect sensors supplied in the market, by rejecting noise and providing accurate measurement over significantly larger distances. The development of this sensor has applications beyond this specific medical device.

High Resolution Oesophageal Manometry: Addressing Thermal Drift

Introduction High resolution manometry (HRM) is a sophisticated and widely used technology allowing detailed examination of oesophageal function. A described limitation of the HRM system is its propensity to ‘thermal drift’. Thermal drift is a false change in the measured pressure attributed to the change from ambient to body temperature. In prolonged studies this effect can be marked. We sought to investigate the nature and magnitude of this phenomenon and to validate the currently employed corrections. Methods Six experiments were performed with the HRM catheter placed in a water bath at a constant depth and temperature of 37°C. Recordings were carried out for 2 h. Pressure readings for the thirty-six sensors were plotted against time. Results The mean pressure change for six experiments and thirty six sensors was 13.1 mmHg (range 1.9–44.7 mmHg). The rate of drift varied between sensors and for an individual sensor between experiments. For an individual sensor within an experiment the pressure increase was linear (R2 > 0.9 in 211 of 216 graphs). In the standard correction for thermal drift, the pressure increase in each sensor at the end of the study is subtracted from the data set to reset the baseline. This was replicated in the recorded pressures and the residual error calculated. The mean error increased with study duration and for a given study was maximal for the early data. For data captured at the start of a 15-min study the mean error with 95% confidence intervals was 1.4 +/− 0.12 mmHg. Corresponding values for a 30-min study were 2.8 +/− 0.24 mmHg and for a 60-min study 6.1 +/− 0.52 mmHg. The distal border of the lower oesophageal sphincter, used to calculate sphincter length, is defined by an increase in pressure of 2 mmHg from intragastric pressure. Errors of this magnitude therefore have the potential to affect measured physiological parameters. A linear correction was then applied to the data, using the best fit line for each sensor within each experiment. For this tailored correction the mean error with 95% confidence intervals was 0.4 +/− 0.017 mmHg and was independent of study duration. Conclusion Thermal drift is better considered as ‘Baseline drift’ a continuous upward drift of the baseline pressure with time rather than a ‘once and for all’ baseline change. A correction process which takes into account the ongoing and linear nature of the drift reduces the error associated with this phenomenon. Incorporating this correction into existing software would improve the accuracy of the system without impact on ease of use.

428 Characterization of Proximal Movement of Gastro-Oesophageal Junction During Transient Lower Oesophageal Sphincter Relaxations Using a Novel Hall Effect Probe

alcohol etiology were more likely to be male (65 vs. 36%, p<0.05), Black (18 vs. 4%, p= 0.04) and smokers (88 vs. 29%, p<0.01). Over a median follow up (which was similar across etiologies) of 9 years (IQR 6, 15), progression to CP occurred in 20 (18%) patients. The mean age at the time of CP diagnosis was 48 +/17 years and the median duration from the first episode of AP to the diagnosis of CP was 7 years (IQR 4, 13). The overall risk of progression to CP was significantly higher in patients with alcohol (vs. others) etiology (41 vs. 14%, p<0.05). On Cox-regression analysis, the risk of progression from AP to CP was 3 fold higher in patients with alcohol etiology (HR 3.1, 95% CI 1.2-7.7) (Figure 1). Conclusions: Progression from RAP to CP, although frequent in patients with alcohol etiology, also occurs in a subset of patients with other etiologies.

The development of squamo-columnar junction locator probe and its performance on bench studies

Introduction The position of the squamo-columnar (SC) junction is constantly changing and this precludes accurate monitoring of acid exposure of the most distal oesophagus. The authors have developed a novel probe to allow continuous monitoring of the SC junction location. The method involves endoscopically clipping a small magnet (2 mm diameter and 1 mm thick) to the SC junction and monitoring its position relative to the probe comprising 26 Hall Effect sensors mounted at 5 mm spacing on a circuit board contained within a silastic tube (diameter 3.2 mm). The aim of the current study was to assess the accuracy of the system on the bench. Methods The accuracy was determined by comparing the recorded position of the magnet along the length of the probe with its actual position along the probe. This was assessed with the magnet in various rotations and orientations both anterior and posterior to the probe and various distances away from the probe. As the conductive property of Hall Effect sensors is dependent on temperature, bench studies were performed to assess effects of rising temperature on the systems accuracy. The potential electro-magnetic interference of the locator probe with multi-channels pH probe (Synectics, UK) and solid state high resolution manometer (Synmed, UK) was also investigated. Results The accuracy was related to the distance between magnet and probe, orientation of the field of the magnet relative to the probe and whether the magnet was positioned anterior, posterior or lateral to the probe. Greatest accuracy was with the magnet anterior to the probe and its magnetic field perpendicular to the length of probe with position errors of ±2.3, ±2.9, ±2.7 mm at 5, 10 and 15 mm distance from the probe respectively. The poorest accuracy was with the magnet lateral to the probe and its magnetic field horizontal to the line of the probe, with position errors of ±2.3, ±7.1, ±7.9 mm at 5, 10 and 15 mm distance from the probe respectively. Over 95% of all studied orientations, an accuracy of less than ±10 mm was achieved up to a distance of 15 mm between the magnet and the probe. Increase in temperature from 20°C to 37°C did not affect accuracy of the system even though it reduces the magnetic field strength. The manometer had a minor impact on the systems accuracy due to metallic properties of its sensors but no interference was seen with the pH probe. Conclusion This technique should allow monitoring of the location of the SC junction to an accuracy greater than that of currently available high resolution manometry or multiple pH sensor devices.

Squamo-columnar junction locator probe: an in vivo validation study

Introduction The gastro-oesophageal junction is very mobile and constantly changing position with breathing, swallowing and transient lower oesophageal sphincter relaxation (TLESR). The only method currently available for studying its location is fluoroscopic screening and this is limited by radiation exposure. We have developed a method allowing continuous real-time monitoring of the squamo-columnar (SC) junction without radiation exposure. It involves clipping a small magnet endoscopically to the SC junction and monitoring its location by a series of 26 Hall Effect sensors placed at 5 mm interval within a probe placed in oesophageal lumen. The aim of the study was to validate the new technique against fluoroscopy. Methods In eight subjects, the magnet was attached and locator probe inserted. During simultaneous fluoroscopy, subjects were asked to perform normal breathing, deep breathing, water swallows and finally advancement and retraction of locator probe over 12 cm segment. The fluoroscopy recorded images at a rate of 5 frames per seconds and the locator at 8 Hz. The position recorded by fluoroscopy and locator at each second interval were compared as well as amplitude of each complete manoeuvre. Results The correlation co-efficient for all 224 position readings was 0.96 (95% CI 0.89 to 0.96) and adjusted residual squared (R2) of 0.91. The amplitude for the different manoeuvres was similar by the two techniques (see table 1). Table 1 PWE-123 Comparison and correlation of data from locator probe and fluoroscopy screening Manoeuvre (N; n) Correlation co-efficient (95% CI) Adjusted R2 Median fluoroscopy amplitude (mm) Median locator amplitude (mm) Normal breathing (N=6, n=24) 0.94 (0.93 to 1.28) 0.88 5.50 5.17 Deep breathing (N=10,n=66) 0.95 (0.91 to 1.07) 0.90 12.25 12.01 Water Swallow (N=7,n=55) 0.92 (0.58 to 0.94) 0.84 25.00 26.23 Insertion and Withdrawal (N=6,n=80) 0.95 (0.82 to 0.96) 0.90 92.80 85.59 N; number of events, n; number of 1 s interval data points from events, R2; residual squared, mm; millimetres Conclusion The locator allows continuous monitoring of the location of the SC junction with an accuracy equivalent to fluoroscopic screening and without any radiation exposure.