Apnea-Associated Reduction in Lower Esophageal Sphincter Tone in Premature Infants

Objective

To characterize esophageal motility during episodes of prolonged apnea in premature infants.

Study design

We retrospectively reviewed combined manometric and physiological monitoring studies performed in tube-fed premature infants from 1994 to 2002. Apnea was defined as a respiratory pause of >20 seconds. For each apneic event, pharyngeal swallowing, esophageal motility, and lower esophageal sphincter (LES) pressure were assessed before, during, and after apneic episodes.

Results

Twelve episodes of apnea (duration, 20 to 120 seconds) were identified in 7 infants (34 to 37 weeks postmenstrual age (PMA); study weight, 1950 to 2380 g). During the apneic epsisodes, swallowing increased (median[interquartile range], 0[0,0], 5[4,7], and 1[0,2] swallows/minute before, during, and after apnea, respectively; P < .05), esophageal pressure wave sequences (PWS) increased (1[0,2], 5[3,6], and 2[1,3] PWS/minute before, during, and after apnea, respectively; P < .05) and LES pressure decreased (16[12,21], 6[5,8], and 27[12,32] mmHg before, during, and after apnea, respectively; P < .05).

Conclusion

In premature infants, apnea is associated with reduced LES tone, potentially increasing the likelihood of reflux occurring after the onset of apnea.

Abbreviations: GER, Gastroesophageal reflux, LCR, Laryngeal chemoreceptor reflex, LES, Lower esophageal sphincter, PMA, Postmenstrual age, PWS, Pressure wave sequence, SLN, Superior laryngeal nerve, TLESR, Transient lower esophageal sphincter relaxation