Spatiotemporal characteristics of acid refluxate and relationship to symptoms in premature and term infants with chronic lung disease.

BACKGROUND AND OBJECTIVES

The prevalence of gastroesophageal reflux (GER) is high among infants with chronic lung disease (CLD), and the associated pathogenic mechanisms are not clear. The relationship of symptoms to the extent or duration of acid reflux events (AREs) is not well known in preterm or term infants. Our aim was to evaluate the relationship between spatial (height) and temporal (duration) characteristics of AREs (pH <4.0) with symptoms in CLD. We tested the hypothesis that in infants with CLD, AREs into the pharynx are associated with increased symptom occurrence and delayed clearance.

METHODS

Nine infants born at 29.8 +/- 5.5 wk gestation (mean +/- SD, range 24.7-39.0 wk) with CLD were evaluated for GER at 49.7 +/- 8.0 wk postmenstrual age (mean +/- SD, range 39.9-67.4 wk). Esophageal manometry was first performed to determine the nares-lower esophageal sphincter (LES) distance. A pH-impedance probe was placed at 87% of the nares-LES distance, and a recording was performed for about 24 h at cribside. Symptoms (respiratory, sensory, and movement) were documented by nurses that were blinded to the pH-impedance recordings. A symptom was considered associated with an ARE if it occurred 2 min before, during, or 2 min after the ARE. The proximal extent and associated clearance mechanisms were correlated with symptom sensitivity index (SSI = number of AREs with symptoms/total AREs *100). Multiple logistic regression methods, analysis of variance (ANOVA) models, and chi(2) tests were performed. Data are described as median, mean +/- SD, or %.

RESULTS

A total of 511 AREs, based on pH-Impedance methods, were analyzed from 203 h of recordings in the nine infants. The distal esophagus was the maximal height reached in 80% of AREs (P < 0.001, compared to other esophageal segments). Overall 33% of the AREs were associated with symptoms, and an SSI of 77% was noted with high AREs into the pharynx. The average acid clearance time was prolonged with symptomatic AREs versus nonsymptomatic AREs by 3.5-fold (P < 0.001).

CONCLUSIONS

The occurrence and frequency of symptoms with AREs depend on the most proximal extent of the ARE and the acid clearance time.