Background/Aims: Measurements of mucosal impedance can detect GERD with high levels of specificity and positive predictive values. However, it remains unclear whether mucosal impedance changes frequently during a day and is influenced by the time from the meal period and sleeping time. The aim of the study was to investigate factors influencing on esophageal baseline impedance levels, such as time from the meal period, sleep onset, and the location of measurement, in patients with suspected symptoms of GERD.
Methods: Consecutive endoscopy-negative patients with suspected symptoms of GERD such as heartburn, chest pain, and/or globus who underwent 24h esophageal multichannel intraluminal impedance-pH (MII-pH) monitoring were eligible for inclusion in this study. Baseline impedance was measured in the proximal esophagus (the average of 15 and 17 cm) and the distal esophagus (the average of 3 and 5 cm) at 5 min before meal, 5 min after the meal period, 30 min after the meal period, 30 min before sleep, 30 min after sleep onset and 60 min after sleep onset. Each single baseline value represents the average value of a 30-s time period around each time point.
Results: Baseline impedance levels did not significantly differ according to gender or age. Baseline impedance levels at 5 min and 30 min after meal were significantly lower in the proximal (p<0.001) and distal esophagus (p<0.001), compared with those at 5 min before meal. Significantly lower baseline impedance levels were observed at 30 min (p<0.005) and 60 min (p<0.005) after sleep onset in the proximal esophagus, compared with those at 30 min before sleep onset, but not in the distal esophagus. Baseline impedance levels in the distal esophagus were significantly lower in patients with pathologic reflux, compared with the GERD-unrelated group. No significant difference in the baseline impedance levels was observed between patients with positive symptom index alone and the GERD-unrelated group.
Conclusions: The time from the meal period or sleep onset, and the presence of pathological acid reflux or pathological bolus reflux appear to influence on esophageal baseline impedance levels. However, sex, age, and the presence of esophageal hypersensitivity do not seem to be associated with esophageal baseline impedance levels.
