Clinical relevance of esophageal baseline impedance measurement: just an innocent bystander.
The clinical relevance of esophageal baseline impedance (BI) remains to be determined. In the present study, we explored the impact of gastroesophageal reflux disease (GERD) and esophageal dysmotility on BI. A total of 18 children with esophageal atresia, 26 children with GERD, and 17 controls prospectively underwent esophagogastroduodenoscopy and pH-impedance monitoring. BI was measured in both proximal and distal esophagus. Gastroesophageal reflux (GER) and bolus transit indicators were defined according to published criteria. Patients with esophageal atresia showed significantly lower proximal and distal BI values (952 [716-1811] Ω; 895 [284-1189] Ω; respectively) compared with those with GERD (3015 [2368-3975] Ω; 2231 [1770-3032] Ω, P < 0.001 and <0.001, respectively) and controls (3699 [3194-4358] Ω; 3522 [2927-3994] Ω, P < 0.001 and <0.001, respectively). Using linear regression, proximal BI strongly correlated with total bolus transit time (r(2) = 0.61, P < 0.001) and bolus presence time (BPT; r(2) = 0.63, P < 0.001). Distal BI weakly correlated with acid exposure time (r(2) = 0.16, P < 0.01) and longstanding reflux episodes (r(2) = 0.17, P < 0.01), and strongly correlated with total bolus transit time (r(2) = 0.53, P < 0.001) and BPT (r(2) = 0.58, P < 0.001). By logistic regression, BPT predicted low proximal BI values (odds ratio [OR] 1.052; P < 0.05), whereas both GER indicators (acid exposure time: OR 1.56, P < 0.05; longstanding reflux episodes: OR 2.8, P < 0.05) and BPT (OR 1.66, P < 0.01) predicted low distal BI values. Along the length of esophagus, both bolus transit variables and GER significantly affect BI. This suggests that BI may merely mirror phenomena occurring within the esophageal lumen or wall, limiting its value as a discrete clinical entity to replace variables already used for assessing both GERD and esophageal dysmotility.