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).