Gestational and postnatal modulation of esophageal sphincter reflexes in human premature neonates

Background: Effects of gestational age (GA) and postnatal maturation on upper and lower esophageal sphincter (UES and LES) reflex development remain unclear. We hypothesized very-preterm (VPT) born neonates (< 32 wk GA) have delayed maturation of UES contractile reflex (UESCR) and LES relaxation reflex (LESRR) vs. preterm (PT) born (32–37 wk GA) neonates. Methods: Using provocative manometry, effects of 1,263 graded mid-esophageal stimuli (air, liquid) on sensory-motor characteristics of UESCR and LESRR were investigated in 24 VPT-born and 12 PT-born neonates (37.8 ± 0.6 vs. 38.9 ± 0.4 wk postmenstrual age respectively, P = 0.14). Results: In response to liquid stimuli (vs. air), VPT-born neonates displayed prolonged UESCR and LESRR response latencies ( P < 0.001) and prolonged UESCR and LESRR durations ( P < 0.01); unlike PT-born neonates, who exhibit prolonged LESRR response latency ( P < 0.01), but similar UESCR and LESRR durations ( P = 0.2). Differences were noted in LESRR duration in VPT vs. PT neonates for air stimuli ( P = 0.04). With liquid stimuli, increasing GA was associated with decreasing response onset latencies to UESCR and LESRR ( P < 0.05), and increasing LESRR duration ( P = 0.02). Conclusion: Using GA as categorical or continuous variable, vagus-mediated mechano-sensitive and liquid-sensitive reflex characteristics of UESCR and LESRR are distinct; LESRR differs with varying intrauterine maturation suggesting inhibitory modulation progresses with advancing maturation.