Nocturnal Gastroesophageal Reflux Revisited by Impedance-pH Monitoring

BACKGROUND/AIMS Impedance-pH monitoring allows detailed characterization of gastroesophageal reflux and esophageal activity associated with reflux. We assessed the characteristics of nocturnal reflux and esophageal activity preceding and following reflux. METHODS Impedance-pH tracings from 11 healthy subjects and 76 patients with gastroesophageal reflux disease off acid-suppressive therapy were analyzed. Characteristics of nocturnal supine reflux, time distribution and esophageal activity seen on impedance at 2 minute intervals preceding and following reflux were described. RESULTS Patients had more nocturnal reflux events than healthy subjects (8 [4-12] vs 2 [1-5], P = 0.002), with lower proportion of weakly acidic reflux (57% [35-78] vs 80% [60-100], P = 0.044). Nocturnal reflux was mainly liquid (80%) and reached the proximal esophagus more often in patients (6% vs 0%, P = 0.047). Acid reflux predominated in the first 2 hours (66%) and weakly acidic reflux in the last 3 hours (70%) of the night. Most nocturnal reflux was preceded by aboral flows and cleared by short lasting volume clearance. In patients, prolonged chemical clearance was associated with less esophageal activity. CONCLUSIONS Nocturnal weakly acidic reflux is as common as acid reflux in patients with gastroesophageal reflux disease, and predominates later in the night. Impedance-pH can predict prolonged chemical clearance after nocturnal acid reflux.