Figure 5 - An example of temporal relationship of deglutitive (10-mL barium swallow) nasopharyngeal closure (NPC) with other swallowing events.

NPC-O, onset of NPC; NPC-C, complete NPC; NPO-O, onset of nasopharyngeal opening; NPO-C, complete nasopharyngeal opening; VPC-O onset of velopharyngeal closure; VPC-C, complete velopharyngeal closure; VPO-O, onset of velopharyngeal opening; VPO-C, complete velopharyngeal opening; UESR-O, onset of upper esophageal sphincter relaxation; BA-PX, arrival of barium at the pharynx; VC-O, onset of vestibular closure; VC-C, complete vestibular closure; VO-O, onset of vestibular opening; VO-C, complete vestibular opening. As shown, endoscopically identifiable onset of NPC occurs earlier (0.1 0.02 second) than fluoroscopically seen at onset of velopharyngeal closure, and UES opening occurs while nasopharynx is closed. (Source: Dua et al.¹⁰ with permission from the American Physiological Association)