Normal values for pharyngeal pH monitoring

Objectives: We performed a prospective study of asymptomatic adult volunteers to establish normative values of pharyngeal pH using a novel pH probe. Methods: The Dx-pH probe is a novel pH device capable of measuring liquid and aerosolized acid levels. Twenty asymptomatic patients (Reflux Symptom Index less than 10 and Reflux Finding Score less than 6) underwent simultaneous investigation with this probe placed in the oropharynx and a dual antimony probe placed in the hypopharynx and esophagus. The reflux parameters measured from the oropharyngeal probe included the percentage of time and the number of events in which the pH was less than 5.5, 5.0, 4.5, and 4.0. Results: The upper limits of normal (95th percentile) for the number of events below pH of 5.5, 5.0, 4.5, and 4.0 per 24-hour period were 16.6, 10.7, 7.4, and 0.2, respectively. The upper limits of normal (95th percentile) for an acid exposure time below pH of 5.5, 5.0, 4.5, and 4.0 per 24-hour period were 820 seconds, 385 seconds, 75 seconds, and 3 seconds, respectively. Conclusions: Normative pharyngeal pH values are presented. Further studies are required to determine clinical relevance.