Supplementary Material for: Association between esophageal baseline impedance levels and reflux parameters suggesting defensive mechanisms

Introduction: Ambulatory multichannel intraluminal impedance-pH monitoring (MII-pH) and high-resolution esophageal manometry (HRM) are commonly performed to objectively assess pathologic reflux and understand the pathomechanism in individuals with reflux symptoms. This study aimed to investigate the relationship between novel MII-pH parameters and other metrics in patients experiencing refractory reflux symptoms.
Methods: This retrospective study included patients with persistent reflux symptoms who underwent both HRM and MII-pH assessments. We evaluated total acid exposure time (AET), total bolus exposure time (BET), total number of reflux episodes, post-reflux swallow-induced peristaltic wave index (PSPW-I), and mean nocturnal baseline impedance (MNBI) from MII-pH data. The mean distal contractile integral (DCI) during swallows was derived from HRM.
Results: In this cohort of 55 patients (30 females, median age 58 years), 9 (16.4%) exhibited AET >6.0%, 16 (29.1%) experienced >80 reflux episodes, and 17 (30.9%) had ineffective esophageal motility. Median (10%–90%) MNBI values for Z5 and Z6 were 2140 (258–4046) ohms and 1680 (158–3994) ohms, respectively. Median PSPW-I (10%–90%) was 0.31 (0.07–0.59). MNBI at Z5 and Z6 showed positive correlations with DCI and negative correlations with ineffective swallows, AET, BET, acid clearance time, bolus clearance time, and total reflux episodes (P<0.05). PSPW-I exhibited positive correlations with DCI and negative correlations with ineffective swallows, AET, BET, total reflux episodes, and bolus clearance time (P<0.05). Additionally, MNBI values at Z4, Z5, and Z6 correlated with PSPW-I (P<0.05).
Conclusion: MNBI are associated with both the quantitative reflux index and defensive parameters against reflux.