Esophageal acid exposure in upright and recumbent postures: roles of lower esophageal sphincter, esophageal contractile and transport function, hiatal hernia, age, sex, and body mass.
This study aimed to assess, using multiple regression analyses, the roles of lower esophageal sphincter, esophageal contractile and transport function, hiatal hernia, age, sex, and body mass for esophageal acid exposure in upright and recumbent postures and for esophagitis. In 116 patients with reflux symptoms, acid exposure was recorded by 24-hr pH monitoring, motility manometrically, bolus transport scintigraphically, hiatal hernia and esophagitis endoscopically. In upright posture, the percentage time at pH <4 increased significantly with higher body mass index and lower distal esophageal amplitude, the number of episodes >5 min at pH <4 with lower distal amplitude, slower transport, and higher body mass, and the longest episode at pH <4 with lower distal amplitude. In recumbency, the percentage time at pH <4 increased with lower percentage of effective esophageal contraction waves and male sex, and the number of episodes and the longest episode with lower percentage effective waves. The severity of esophagitis augmented with slower supine transport and male sex. In both postures, acid exposure and esophagitis seem to be determined primarily by impaired esophageal motility and the ensuing slow bolus transport rather than by compromised lower esophageal sphincter function and the presence and size of a hiatal hernia.