Dual site ambulatory pH monitoring: a probe across the lower esophageal sphincter does not induce gastroesophageal reflux.

Background: Twenty-four-hour ambulatory pH studies have traditionally been performed with placement of the pH electrodes proximal to the lower esophageal sphincter (LES). More recently, simultaneous gastric and esophageal pH monitoring studies have been performed to allow the simultaneous assessment and correlation of esophageal and gastric pH.

Objectives: The purpose of this study was to determine if pH probe placement across the LES increases esophageal acid exposure either in asymptomatic, healthy volunteers or in symptomatic patients with a documented history of erosive esophagitis.

Methods: Ten healthy volunteers (five female, five male; mean age 27 yr) and 13 patients with endoscopically confirmed erosive esophagitis (seven female, six male; mean age 35 yr) were randomly assigned, in cross-over fashion, into two protocols. The first protocol required placement of a dual antimony pH electrode catheter (2.1-mm outside diameter) across the LES with pH electrodes positioned 5 cm above and 10 cm below the manometrically identified LES. The second protocol required catheter placement 5 cm and 20 cm above the LES. Twenty-four-hour pH monitoring was performed on all subjects. Healthy volunteers were permitted an unrestricted diet and were studied in an out-patient setting. Symptomatic patients were assessed in an inpatient setting on a standardized diet with a refluxogenic dinner meal.

Results: The total number of reflux episodes, number of reflux episodes greater than 5 min, and the fraction of time that pH was less than 4 were evaluated over the total 24-h time period in the upright and supine positions. Nonparametric paired tests including a Wilcoxon signed rank test and a Robust analysis were used for statistical assessment. There was no significant increase in gastroesophageal reflux observed with placement of the pH probe across the LES either in the asymptomatic healthy volunteers or in patients with documented erosive esophagitis. Neither upright nor supine esophageal acid exposures were modified by catheter placement.

Conclusions: Our study results indicate that placement of a 2.1-mm diameter pH probe across the LES does not induce reflux in asymptomatic healthy volunteers or in patients with GERD. Dual site ambulatory pH monitoring with trans-sphincteric pH catheter placement is a valid diagnostic technique that can be applied clinically when required.