Twenty-four-hour MII-pH monitoring and test interpretation
Insertion and analysis of MII-pH probe was conducted as described in previous studies.9,10 The dual-channel MII-pH catheter models (ZAI-BL-54, 55, 56, ComforTEC Z/PH single use probe with 2.3 mm diameter; Sandhill Scientific, Inc., WI, USA) were selected according to the esophageal length of each patient, and inserted by two ENT doctors. Recorded data were manually analyzed by one expert (EUN YG) using a software program (BioView Analysis, Sandhill Scientific, Inc., Highlands Ranch, CO, USA).
The DeMeester score was calculated in the pH1 and pH8 areas as described previously.10 The acid exposure time (%), reflux episode, and longest reflux time (min) at pH1 and pH8 were recorded. The acid exposure time was the total time of acid reflux episodes divided by the monitoring time. Acid reflux episodes was defined as a drop in pH to less than 4 for at least 5 s. The longest reflux time was expressed in minutes.11
Proximal MII parameters were recorded in reference to the two impedance sensors closest to the hypopharynx, and distal MII parameters were recorded in reference to the two impedance sensors closest to the lower esophageal sphincter. Six parameters were evaluated for proximal and distal MII parameters: (i) all reflux time (%); (ii) longest reflux time (min); (iii) number of acid reflux episodes; (iv) number of weak acid reflux episodes; (v) number of weak alkali reflux episodes; and (vi) number of all reflux episodes.
All reflux time (%) was defined as the sum of the bolus clearance time of all individual reflux episodes divided by the monitoring time. Reflux episodes were checked for liquid, gas, and mixed liquid-gas, respectively:9 (i) A liquid reflux episode defined as a retrograde 50% fall in impedance from the mean baseline impedance between the two consecutive impedance sites. (ii) A gas reflux episode defined as a rapid increase (3 kΩ/s) in two consecutive impedance sites with one site showing an absolute value >7 kΩ without swallowing. (iii) A mixed liquid–gas reflux episode defined as gas reflux occurring immediately before or during a liquid reflux episode.12 Proximal and distal reflux episodes (liquid + gas + mixed) were classified based on the pH as acidic (<4), weakly acidic (between 4 and 7), or weakly alkaline (>7).