Combined multichannel intraluminal impedance and pH-metry: a novel technique to improve detection of gastro-oesophageal reflux literature review.

Ambulatory pH monitoring is currently the best method for detection of gastro-oesophageal reflux. However, pH electrodes are able to measure only acid reflux, and therefore, non-acid reflux episodes, a potentially important cause of symptoms, are ignored by this technique. Multichannel intraluminal electrical impedance has recently been proposed as a novel method to overcome the above limitation of pH testing. Impedance (expressed in ohms) is a measure of the total opposition to current flow between adjacent electrodes. As refluxed contents are characterised by different conductivity, which is the inverse of impedance, for the first time a pH-independent accurate and practical qualitative analysis of refluxate is possible. For instance, the conductivity of air is almost zero and then impedance increases compared with baseline, whereas the conductivity of liquid is much higher and the impedance curve decreases remarkably. The combination of electrical impedance with traditional pH monitoring has the only aim of differentiating acid from non-acid liquid reflux. Moreover, the impedance catheter contains multiple pairs of ring electrodes along the oesophagus, so that an exact assessment of the proximal extent of refluxed material can be achieved. From a clinical point of view, electrical impedance + pH-metry could be useful for identifying the number and percent times of gas, acid and non-acid reflux episodes, to improve the yield of symptom index, to evaluate the reasons for poor response of reflux symptoms to proton pump inhibitors and to know the proximal extent of reflux events in patients with atypical symptoms. Thus, this technique has the potential to become a useful tool for improving our knowledge of gastro-oesophageal reflux disease and optimising the management of these patients.