Abstract
OBJECTIVE
1) Ascertain the normal pH values in the aerosolized environment of the nasopharynx in healthy subjects. 2) Utilize a novel pH probe which allows measuring acidity in a non-liquid environment.
METHOD
Between Nov 2009 and Feb 2010, healthy volunteers without a history of reflux or eustachian tube dysfunction were enrolled in the study. A total of 21 patients had a DxpH Measurement System Probe (Restech Corp, San Diego, CA 2006) placed near the torus tubarius in the posterior nasopharynx. Once placed, the single-channel DxpH Probe takes a pH reading every 1.2 second, and sends the data wirelessly from the attached DxTransmitter to a DxRecorder. Throughout the 24-hour study, the patient records clinically relevant information such as meals and symptoms with the push of a button as well as manually in a written diary. A flexible fiberoptic laryngoscopy was performed to ensure proper placement of the probe, and to assess for laryngopharyngeal reflux using the Reflux Findings Score. Upon completion of the study, the pH data and patient information is downloaded from an SD memory card into DxpH DataView software to be viewed, graphed and analyzed.
RESULTS
For normal individuals with no history of reflux or eustachian tube dysfunction, pH values obtained from the nasopharynx ranged from 6.10 to 7.92. The average pH was 7.03 with a standard deviation of 0.69. Eight subjects (40%) had at least one reflux event during the 24-hour pH study. Decreases in pH were considered reflux events if the pH dropped below 5.5 while in the upright position or below 5.0 in the supine position. The average number of reflux events for subjects in the upright position was 0.6 events over a 24-hour period. In the supine position, the average number of reflux events was 0.5 over 24 hours. One patient was found to have 3 significant reflux events in the supine position, with the longest episode lasting 61.2 minutes.
CONCLUSION
Until recently it has been difficult to detect reflux in the upper airway because available pH catheters were developed to measure reflux in a liquid environment such as the esophagus. By utilizing a novel self-condensing pH probe, we were able to successfully perform a 24-hour pH study in the nasopharynx of 20 healthy individuals. It is our conclusion that the average pH for individuals without symptomatic reflux or Eustachian tube dysfunction is about 7.03. Interestingly, approximately 40% of healthy controls were found to have at least one episode of silent reflux.