Reflux definitions in esophageal multi-channel intraluminal impedance

Abstract

Aim: In this study, we aim to propose consensus-based interpretations to enhance both automatic, and manual analysis and then present our recommendations about reflux-related variables to enhance Multichannel Intraluminal (MII) measurements.

Background: Multichannel Intraluminal Impedance-pH (MII-pH) monitoring is the most sensible option to evaluate Gastroesophageal Reflux Disease (GERD), specifically for the patients with normal endoscopy findings, and persistent symptoms without response to Proton Pomp Inhibitor therapy. There were only a few studies on the interpretation of reflux events in MII tracings.

Methods: Several 200 episodes of reflux events were reviewed during several meetings in five steps, to discuss and categorize unresolved issues within existing interpretations, and propose technical principles for accurate characterization of reflux events.

Results: In this study, we show that baseline impedance is determined using a moving average procedure to the impedance data of each channel with a time window of 60 seconds based on this finding; a liquid reflux event is defined as a retrograde 50% drop in baseline impedance, gas reflux event is defined as a rapid increase in impedance greater than 5 kΩ, Mixed liquid-gas reflux is defined as gas reflux occurring immediately before or during liquid reflux.

Conclusion: The reliability of final diagnosis is significantly dependent on the accurate detection of reflux events, which is currently confronting technical limitations. A pathological reflux event propagates to at least three of the impedance sites, according to the literature. We think that taking three impedance locations into account might be too strict.

Keywords: Esophageal reflux; Gastroesophageal reflux; Impedance; Swallow.

Figure 1

An example of a reflux event that was not detected by software (Red line represents reported base for the recording device). Red and green arrows express reflux and swallows respectively

Figure 2

Schematic sketches describing recommended criteria for reflux detection, the vertical and horizontal axis correspond to impedance data at the most distal site and time measures, respectively. For each panel the red solid line is the BI value. Panel (a) describes our recommended amended points for start and stop time of reflux events. Panel (b) is a liquid reflux as impedance value is always below BL. In panel (c), Δ is greater than du_thre; therefore the diagram corresponds to two distinct liquid refluxes. Panel (d) shows a mixed reflux as Δ is smaller than du_thre. Depending on the amount of Δ, each of panels (e) and (f) might be attributed to liquid (Δ<I_thre) or mixed type reflux (Δ> I_thre)

Figure 3

A two-minute interval of MII (Blue patterns) and BI (red curves). The highlighted area represents a pattern at the distal sites which seems to be a liquid reflux, but it starts to act differently at the proximal sites

Figure 4

An unusual reflux pattern, with longer duration at pharyngeal sites