Journal of Neurogastroenterology and Motility : eISSN 2093-0887 / pISSN 2093-0879

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Fig. 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.
J Neurogastroenterol Motil 2023;29:49~57
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