MECHANISMS OF GASTROESOPHAGEAL REFLUX IN HEALTHY PREMATURE-INFANTS

Objectives: The aim of this study was to characterize the motor events responsible for gastroesophageal reflux (GER) and esophageal acid cle arance in a cohort of healthy preterm infants. Study design: Esophagea l motility was recorded for 2 to 3 hours after a feeding in 24 preterm infants, 31 to 38 weeks' postmenstrual age, by using a sleeve-side ho le micromanometric assembly incorporating a pH probe. Results: Sixty a cid GER episodes were recorded by pH probe, and 133 non-acid GER episo des were recorded manometrically by the presence of esophageal common cavities. Of the 193 GER episodes, 159 (82%) were associated with tran sient lower esophageal sphincter relaxation (TLESR). TLESRs were signi ficantly longer in duration than single swallows (15.1 seconds vs 5.6 seconds, P <.001) and had lower nadir pressures (0.8 mm Hg vs 2.3 mm H g, P <.001). A total of 3216 esophageal body pressure waves were analy zed; 70% of swallow-induced pressure waves were peristaltic in sequenc e compared with 5% of swallow-unrelated pressure waves. During periods of esophageal acidification (pH below 4), peristaltic esophageal body pressure wave sequences cleared acid refluxate more effectively than nonperistaltic pressure wave sequences. Conclusions: In healthy preter m infants, TLESRs are the predominant mechanism underlying GER, and es ophageal clearance mechanisms are well developed by at least 31 weeks' postmenstrual age.