Normal values of pharyngeal and esophageal 24-hour pH impedance in individuals on and off therapy and interobserver reproducibility.

BACKGROUND & AIMS: Combined pH and impedance monitoring can detect all types of reflux episodes within the esophageal lumen and the pharynx. We performed a multicenter study to establish normal values of pharyngeal and esophageal pH-impedance monitoring in individuals on and off therapy and to determine the interobserver reproducibility of this technique.
METHODS: We collected ambulatory 24-hour pH-impedance recordings from 46 healthy subjects by using a bifurcated probe that allowed for detection of reflux events in the distal and proximal esophagus and pharynx. Data were collected when subjects had not received any medicine (off therapy) and after receiving 40 mg esomeprazole twice daily for 14 days (on therapy). The interobserver agreement for the detection of reflux events was determined in 20 subjects off and on therapy. Results were expressed as median (interquartile range).
RESULTS: Off therapy, subjects had a median of 32 reflux events (17-45) in the distal esophagus and 3 (1-6) in the proximal esophagus; they had none in the pharynx. On therapy, subjects had a median number of 21 reflux events (6-37) in the distal esophagus and 2 (0-5) in the proximal esophagus; again, there were none in the pharynx. Interobserver agreement was good for esophageal reflux events but poor for pharyngeal events.
CONCLUSIONS: We determined normal values of pharyngeal and gastroesophageal reflux events by 24-hour pH-impedance monitoring of subjects receiving or not receiving esomeprazole therapy. Analyses of esophageal events were reproducible, but analyses of pharyngeal events were not; this limitation should be taken into account in further studies.