OROPHARYNGEAL ACCOMMODATION TO SWALLOW VOLUME

Background & Aims: The oropharyngeal swallow accommodates a range of b olus volumes with substantial impact on its dynamic radiographic appea rance despite being a nearly reflexive sequence. The aim of this study was to analyze the mechanism of volume accommodation. Methods: Coordi nation of the glossopalatal junction, velopharyngeal junction, larynge al vestibule, and upper esophageal sphincter (UES) and intraluminal ph aryngeal dimensions were measured from biplane videofluoroscopic swall owing studies in 8 volunteers during 1- and 20-mL swallows. These meas urements were applied to three-dimensional reconstructions of the phar yngeal swallow, permitting analysis of their effect on intraluminal vo lume and propulsive function. Results: Dividing the pharyngeal swallow into periods of reconfiguration, sustained reconfiguration, and offse t of reconfiguration, volume accommodation occurred by a 0.2-second pr olongation of reconfiguration, preserving the coordination of the onse t and offset events. Augmented reconfiguration increased the dimension s of the pharyngeal chamber, caused more rapid bolus expulsion, and in creased UES distention. However, maximal transphincteric flow per unit area across the UES was constant, showing its compliance. Conclusions : Volume accommodation is accomplished by augmenting and prolonging ph aryngeal reconfiguration from a respiratory to deglutitive pathway. Th is modification in the timing of neurally mediated events is amplified by its mechanical consequences, resulting in the different cineradiog raphic appearance and propulsive attributes of large and small volume swallows.