vMII for Measurement of Oesophageal Bolus Transport and Reflux

Overview

Recent work at St. Thomas' has validated an innovative new design of a multichannel intraluminal impedance (MII) catheter that is sensitive to variation in oesophageal volume in healthy volunteers and patients. This project will establish the clinical value of volume sensitive MII (vMII) compared to conventional MII acquired simultaneously by the same catheter (ROC analysis). Studies will assess: 1. The accuracy of volume measurements and correlation between symptoms and the volume of bolus retention in patients with dysphagia. 2. The accuracy of volume measurements and correlation between symptoms and reflux volume in patients with reflux disease. Follow up studies after appropriate treatment will assess whether symptomatic improvement is associated with a reduction in oesophageal volume retention/reflux. The vMII technique will be applied with high resolution manometry (HRM). These investigations are complementary in that vMII assesses the success or failure of bolus transport (or occurrence of reflux) and HRM can assess: 1. the oesophageal dysfunction that results in bolus escape 2. the abnormal events at the gastro-oesophageal junction (reflux barrier) that allow reflux to occur. with a reduction in oesophageal volume retention / reflux.

Swallowing problems and gastro-oesophageal reflux disease (GORD) are common in the community with important effects on health, quality of life and NHS costs. Furthermore, these problems may explain the increasing rate of oesophageal cancer. These concerns highlight the importance of appropriate investigation and management of these symptoms. Medications that suppress gastric acid relieve symptoms in many patients; however this does not improve oesophageal function or reduce 'non-acid' reflux from the stomach. At least 1 in 4 patients have symptoms despite treatment and further management of these individuals is challenging. Conventional multichannel intraluminal impedance (MII) studies assess swallowing function and reflux, but cannot assess volume. This is important because larger volumes of food stuck in the oesophagus and failure to clear larger amounts of irritant reflux from the stomach are more likely to cause symptoms and damage to the lining of the oesophagus. The proposed project builds on recent work at St. Thomas' in which a new MII technique was shown to detect changes in oesophageal volume. The aim is to assess whether this volume sensitive MII (vMII) is useful in clinical practice. Patients with swallowing problems and reflux symptoms will undergo vMII and High Resolution Manometry in unison in a combined Catheter Assembly during a test meal containing barium (known as videofluoroscopy) as it is visible on x-ray. The volume of fluid stuck in the oesophagus or refluxing from the stomach will be measured by both vMII and videofluoroscopy and the problems with motility will be assessed with HRM. The results will be compared and the link between oesophageal volume, dysmotility and symptoms will be examined. Finally the studies will be repeated after treatment (videofluoroscopy being offered only males and women over 40) to see if improvements are linked to reduced volume measurements. In routine clinical practice, successful vMII would reduce the need for barium swallows (therefore reducing exposure to radiation) and improve the ability to link oesophageal dysfunction and reflux events with symptoms, and thus guide further management in patients that fail to respond to standard treatments. Existing measurements of oesophageal function assess the presence or absence of acid (pH), bolus transport (HRM) or fluid (conventional MII) in the oesophagus, but are not sensitive to volume change. It is thought that this explains the failure to establish the cause of oesophageal symptoms in some patients (Sifrim Gut 06). Firstly because retention and reflux of large volumes in the oesophagus is more likely to cause symptoms. Secondly because conventional MII lacks sensitivity in patients with poor emptying of residual fluid in the oesophagus much of the time (e.g. achalasia, post-fundoplication). Volume sensitive MII (vMII) is a novel adaptation of catheter technology that is sensitive to volume changes in the oesophagus of healthy volunteers (Fox DDW 06). It is a non disposable catheter which is 3mm in diameter and is very similar to the impedance and pH manometry catheters routinely used at St Thomas' and many other hospitals and are well tolerated by patients. Study Design and Methodology Studies will be performed in two, well-defined patient populations that represent the two cardinal presenting symptoms in oesophageal disease. 1. Patients with swallowing difficulty (dysphagia) related to achalasia 2. Patients with reflux symptoms referred for consideration of fundoplication. Individuals (age 18-65 years) referred to the oesophageal laboratory for investigation will be invited to participate. All participants will undergo complete physical and mental health questionnaires, and an assessment of predominant complaint and symptom severity. This study will test two key issues in order to compare the clinical value of volume measurements by vMII to existing techniques in these two patient populations. 1. Stationary: The accuracy of volume measurements acquired by vMII in patients with oesophageal disease compared to videofluoroscopy (gold standard). 2. Ambulatory: The association of volume measurements with symptoms compared to conventional pH / MII measurements before and after treatment.