Vakil N, Ziegler C, Schipper J, Fisk L, Roucher L. Gastroenterology. 2013 May;144(5):S-844.

OBJECTIVES: The aim of this study was (1) to determine if the Restech probe measures vaporized acid in vitro, (2) to determine the concordance of the Restech probe placed in the pharynx with a Bravo pH probe placed in the distal esophagus.

RESULTS: Table 1: There was good concordance between the liquid pH and measurement of pH in vapour. Dehydration of the catheter resulted in activation of detection circuitry within 30 seconds and a pH of 15 was displayed. This pH is pre-programmed to demonstrate error by showing a very high pH. The Bravo probe showed reflux in 9/10 patients in the upright position and the Restech showed upright reflux in 6/10 patients. However, in the supine position, 7/10 Restech studies demonstrated reflux in the laryngo-pharynx with only 2 Bravo studies were positive in the supine period.

CONCLUSION: 1. The Restech probe accurately measures the pH of liquids and the nebulized vapor of liquid. 2. The Restech probe records acidic events that are not recorded by the Bravo pH probe particularly in the supine position. 3. The supine events are not due to drying of the catheter as dessication of the probe is rapidly detected by inbuilt circuitry 4. Nocturnal acidification of the laryngo-pharynx may be important in extra- esophageal GERD.