Acid reflux event detection using the Bravo^TM wireless vs the Slimline^TM catheter pH systems: why are the numbers so different?

John Pandolfino ^1*, Qing Zhang ¹, Mitchal Schreiner ¹, Sudip Ghosh ¹, Michael Roth ¹ and Peter J Kahrilas ²

¹ Northwestern University, United States
² Northwestern University, Feinberg School of Medicine, United States

^* To whom correspondence should be addressed. E-mail: j-pandolfino{at}northwestern.edu.

Accepted 21 March 2005

Abstract

Objective: This study analyzed the relative accuracy of the Bravo^TM wireless and the Slimline^TM catheter-Mark III Digitrapper^TM pH systems in the detection of acid reflux events.

Methods: 25 asymptomatic subjects were studied. A Bravo^TM capsule was placed 6 cm above the squamocolumnar junction (SCJ), marked by an endoclip, and a Slimline^TM pH catheter was placed 5 cm above the manometrically localized LES. The distance between the SCJ and each pH electrode was measured fluoroscopically. An in-vivo pH reference was established using swallows of 100 ml of orange juice (pH 3.88). Concurrent pH data from the two systems was analyzed in Excel spreadsheets.

Results: Significantly more acid reflux events were reported by the Digitrapper system than with the Bravo system (117.0 vs 41.8). This was not explained by electrode position as there was no difference in median distance between the SCJ and either pH electrode (7.25 cm vs 7.08 cm). The dominant source of discrepancy between systems was inaccuracy in electrode calibration and, after adjustment using the in-vivo orange juice pH measurement, the discrepancy improved by 40%. However, discrepancy still existed and was most pronounced in the short reflux events (1-15s for the catheter, 1-17s for the Bravo^TM) associated with minimal intra-esophageal acidity and very poor concordance between systems.

Conclusion: Substantially more reflux events are reported by the Digitrapper^TM system compared to the Bravo^TM system. 40% of excess events were attributable to a flawed software scheme for electrode thermal calibration while most of the remainder were brief events with poor concordance between systems and minimal intra- esophageal acidity.

Keywords: Bravo, Slimline Catheter, pH monitoring, reflux events

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