Development of pharyngo-esophageal physiology during swallowing in the preterm infant N. ROMMEL,*,  , à M. VAN WIJK,*,§ B. BOETS,  , – G. HEBBARD,** R. HASLAM,   G. DAVIDSON*, àà & T. OMARI *, àà *Centre for Pediatric & Adolescent Gastroenterology, Children, Youth & Women’s Health Service, Women’s and Children’s Hospital, North Adelaide (SA), Australia  Department of Neurosciences, Experimental Otorhinolaryngology, University of Leuven, Leuven, Belgium àNeurogastroenterology Clinic, University Hospital Gasthuisberg, Leuven, Belgium §Department of Pediatric Gastroenterology & Nutrition, Emma Children’s Hospital AMC, Amsterdam, The Netherlands –Child and Adolescent Psychiatry, University Hospital Leuven, Leuven, Belgium **Department of Gastroenterology, Royal Melbourne Hospital, University of Melbourne, Melbourne (Vic.) Australia   Department of Neonatal Medicine, Children, Youth & Women’s Health Service, Women’s and Children’s Hospital, North Adelaide (SA), Australia ààDepartment of Pediatrics, University of Adelaide, Adelaide (SA), Australia Abstract Background Poor feeding is a common cause of pro- longed hospitalization of preterm infants. Pharyngeal and upper esophageal sphincter (UES) function of preterm infants has been technically difficult to assess and is therefore poorly characterized. The aim of this study was to assess the development of pharyngeal motility, UES function, and their coordination during nutritive swallowing in preterm infants. Methods Development of swallowing was assessed in 18 preterm infants. High resolution manometry was performed at first oral feeding attempt (31–32 week) and then weekly for 4 weeks. Pharyngeal and UES pressure changes were characterized in 980 swallows. Key Results During swallowing, we observed an age- related increase in peak pharyngeal pressure at the laryngeal inlet (1 cm above UES) but an age-related decrease in the time required for the UES to fully relax to nadir. Analysis of the timing of proximal pharyngeal contractile peak and UES nadir showed that the UES was not fully relaxed when bolus propulsive forces were at their peak in the youngest infants. Conclusions & Inferences Results show developmental changes in infant swallow physiology that can be clearly linked to the effectiveness of nutritive swallowing. Most preterm infants demonstrated poor pharyngeal pres- sures at the laryngeal inlet coupled with poor coordi- nation of pharyngeal propulsion with UES relaxation. These pressure patterns were less efficient than those demonstrated by older infants who were more adept at feeding. These observations may explain why in- fants under 34 weeks are physiologically unable to feed effectively and experience frequent choking and fatigue during feeding. Keywords deglutition, manometry, motility, premature infant, upper esophageal sphincter. Abbreviations: UES, upper esophageal sphincter; HRM, high resolution manometry; CA, corrected age; MMA, mixed model analysis; PE, Pharyngo-esophageal. INTRODUCTION The newborn infant relies on its ability to suck and swallow fluids to obtain safe and successful oral feeding. 1–3 In the very preterm infant, the oral feeding capacity is poor due to inadequate suck–swallow– breath coordination and leads to suboptimal nutrition and growth. 3–7 With overall survival rates in these infants increasing, dysphagia is becoming a major clinical problem prolonging hospitalization and increasing health care costs. 7 Research over the last 20 years focused predom- inantly on the development of sucking being the main aspect of the oral preparatory stage of Address for Correspondence Nathalie Rommel, Department of Neurosciences, ExpORL, Faculty of Medicine, University of Leuven; Neurogastroente- rology Clinic, Gasthuisberg University Hospital, Leuven, Belgium and Herestraat 49 (PO 721) 3000 Leuven, Belgium. Tel: +321 633 0485; fax: +321 633 0486; e-mail: nathalie.rommel@med.kuleuven.be Received: 13 January 2011 Accepted for publication: 11 July 2011 Neurogastroenterol Motil (2011) 23, e401–e408 doi: 10.1111/j.1365-2982.2011.01763.x Ó 2011 Blackwell Publishing Ltd e401