Differentiation of Esophageal pH-Impedance Characteristics Classified by the Mucosal Integrity Marker in Human Neonates

BACKGROUND: In adults, distal baseline impedance (BI) is a determinant of esophageal mucosal integrity with values <900Ω indicating inflammation. Relationships between acid gastroesophageal reflux (GER) and BI in neonates are unclear. METHODS: NICU infants (N=198, 30.4±0.3 weeks gestation) were evaluated at 43±0.4 weeks postmenstrual age using 24-hour pH-impedance. Ten randomly selected one-minute windows during rest from the distal impedance channel (Z6) were averaged. Chi-square, t-tests, and ANOVA were used to compare pH-impedance and symptom characteristics by BI severity (BI<900Ω, BI 900-2000Ω, BI>2000Ω). Regression analysis was used to identify potential contributing factors of BI. RESULTS: In BI<900Ω: 1) pH-impedance characteristics were increased (acid reflux event frequency, duration, and severity, all P<0.05 vs. BI>2000Ω), and 2) positive symptom correlations were noted with bolus (73%) and acid events (55%). Significant predictors of BI included chronological age, acid reflux index, and BPD diagnosis (all P<0.05). CONCLUSIONS: Low BI is associated with prolonged acid exposure, delayed clearance, and greater aerodigestive symptom prevalence, likely associated with inflammation and or increased mucosal permeability. BI>2000Ω likely involves little or no inflammation because acid exposure is minimal. Combination of SAP, pH-impedance metrics and BI along with clarification of dysmotility mechanisms provides the rationale for personalized anti-reflux therapies as needed.