Objective: We aimed to analyze the results of 24-h multichannel intraluminal impedance and pH-monitoring (MII-pH) of the laryngopharynx and esophagus in asymptomatic volunteers. Moreover, we also aimed to gain insight into and establish a baseline for laryngopharyngeal reflux in the healthy population by quantitatively and qualitatively comparing the reflux and pH distribution in both the laryngopharynx and the esophagus.
Methods: Healthy volunteers were recruited and observed; they underwent 24-h ambulatory combined MII-pH monitoring. The proximal sensor (pH1) was positioned approximately 1 cm above the upper esophageal sphincter with the aid of a solid-state high-resolution esophageal manometer. Laryngopharyngeal reflux events were detected and characterized by the incidence and property of reflux both in the laryngopharynx and the esophagus.
Results: Thirty-eight asymptomatic volunteers who completed all the examinations were included in this study. The median pH detected by the proximal sensor was 6.6 (6.2, 7.0), with an average of 6.58 ± 0.74. A total of 814 laryngopharyngeal reflux events were detected, including 722 (89%) in the upright position and 92 (11%) in the supine position with incidence (0%) in the liquid state, 44 (5%) in the mixture, and 769 (95%) in the gaseous state. Furthermore, 5 incidences (1%) of acid reflux and 809 incidences of non-acid reflux (99%) were noted. A total of 5779 esophageal reflux events were detected, including 5020 (87%) in the upright position, 759 (13%) in the supine position, with 2051 (36%) in the liquid state, 2050 (35%) in the mixed condition, and 1678 (29%) in the gaseous state; adding up to 805 incidences (14%) of acid reflux and 4974 incidences (86%) of non-acid reflux.
Conclusion: Non-acid reflux in the upright position is characteristic of laryngopharyngeal reflux. Acid reflux is almost undetectable in healthy subjects. Hence, the diagnostic indicators of gastroesophageal reflux disease are not suitable for laryngopharyngeal reflux disease.
Keywords: Asymptomatic volunteers; Gas reflux; Laryngopharyngeal reflux disease; Multichannel intraluminal impedance and pH monitoring (MII-pH); Non-acid reflux.