Validation of Pharyngeal Acid Reflux Episodes Using Hypopharyngeal Multichannel Intraluminal Impedance-pH

Abstract

Background/aims: Hypopharyngeal multichannel intraluminal impedance-pH (HMII-pH) technology incorporating 2 trans-upper esophageal sphincter impedance channels has been developed to detect pharyngeal reflux. We used the HMII-pH technique to validate the candidate pharyngeal acid reflux (PAR) episodes based on the dual-pH tracings and determined the interobserver reproducibility.

Methods: We conducted a cross-sectional study in tertiary centers in Taiwan. Ninety patients with suspected laryngopharyngeal reflux and 28 healthy volunteers underwent HMII-pH test when off acid suppressants. Candidate PAR episodes were characterized by pharyngeal pH drops of at least 2 units and reaching a nadir pH of 5 within 30 seconds during esophageal acidification. Two experts manually independently identified candidate PAR episodes based on the dual-pH tracings. By reviewing the HMII-pH tracings, HMII-pH-proven PAR episodes were subsequently confirmed. The consensus reviews of HMII-pH-proven PAR episodes were considered to be the reference standard diagnosis. The interobserver reproducibility was assessed.

Results: A total of 105 candidate PAR episodes were identified. Among them 84 (80.0%; 95% CI, 71.0-87.0%) were HMII-pH-proven PAR episodes (82 in 16 patients and 2 in 1 healthy subject). Patients tended to have more HMII-pH-proven PAR episodes than healthy controls (median and percentile values [25th, 75th, and 95th percentiles]: 0 [0, 0, 3] vs 0 [0, 0, 0], P = 0.067). The concordance rate in diagnosing HMII-pH-proven PAR episodes between 2 independent observers was 92.2%.

Conclusion: Our preliminary data showed that 80.0% (71.0-87.0%) of the proposed candidate PAR episodes were HMII-pH-proven PAR episodes, among which the interobserver reproducibility was good.

Keywords: Acids; Esophagus; Gastroesophageal reflux.

Figure 1

Configuration of the hypopharyngeal multichannel intraluminal impedance-pH catheter for detection of pharyngeal acid reflux. The catheter was selected based on the participants’ esophageal length. The catheter incorporates 2 trans-upper esophageal sphincter (UES) impedance channels to differentiate refluxes from swallows, 2 proximal esophageal ones, and 2 distal esophageal ones. The 2 pH probes were located at 1 cm above the UES and 5 cm (± 1 cm) above the lower esophageal sphincter (LES).

Figure 2

Examples of representative artifacts, swallows, and pharyngeal acid reflux (PAR) episodes based on visual analyses of 1-hour window screening (step 1) and adequate zooming in (step 2) of the dual pH tracings. Final diagnosis was made based on the magnified hypopharyngeal multichannel intraluminal impedance-pH (HMII-pH) tracings (step 3). (A) Synchronous pH drops were characterized as onset of pH drops occurring simultaneously in both pharyngeal and esophageal channels during adequate zooming in (solid vertical line in step 2), which were most likely due to equipment errors. Moreover, abrupt pH return to baseline (arrowhead) also simultaneously occurred in both channels. (B) Antegrade pH drops were characterized as pharyngeal pH drops followed by esophageal pH drops, in which an acidic liquid swallowing episode outside of meals was diagnosed by HMII-pH tracings (step 3). (C) Retrograde pH drops characterized as pharyngeal pH drops (vertical line), preceded by esophageal pH drops. However, simultaneous abrupt pH return to baseline (arrowhead) in both channels (step 2) suggests artifacts, which were subsequently proved by HMII-pH tracings in step 3. (D) Retrograde pH drops typically occur in a PAR episode when an esophageal pH drop is followed by a pharyngeal pH drop. (E) Retrograde pH drops could also exist in a PAR episode during a prolonged or pre-existing esophageal acidification. (F) Retrograde pH drops due to acidic liquid swallows (arrowhead) may occur immediately after a PAR episode, suggesting a possibility of re-swallowing hypopharyngeal acidic refluxate.

Figure 3

Number of candidate pharyngeal acid reflux (PAR) episodes (A) and hypopharyngeal multichannel intraluminal impedance-pH (HMII-pH)-proven PAR episodes (B) detected by 2 independent observers. Gray zone represents episodes by 3 experts’ consensus reviews.