Identifying the Timing of Swallowing Sounds Using Videoendoscopy Findings in Healthy Adults

Cervical auscultation is a useful tool for detecting dysphagia; however, the sites where swallowing sounds are produced are unknown. In this study, we investigated the relationship between swallowing sounds and videoendoscopy (VE) images in healthy adults to identify the timing of swallowing sounds. Fifteen healthy young adults participated in the study. Each participant was seated in an upright position while a stethoscope probe with an inserted microphone was placed at the center of his or her lower neck to detect swallowing sounds during the VE. The detected sounds were recorded simultaneously with the VE images while the subjects swallowed 4g of liquid or jelly. Swallowing duration, swallowing sound duration, and VE findings at the beginning and end of swallowing sounds were analyzed. One hundred and thirty-four sound samples produced by a single swallowed bolus were obtained and analyzed. The mean swallowing duration for each material ranged from 1.25 to 2.39s. Swallowing duration was significantly longer for jelly compared with liquids (p<0.01). Swallowing sound duration was approximately 0.5s in all samples, and there were no significant differences between materials. Most swallowing sounds started during velopharyngeal closure (109/134, 81.3%), and most swallowing sounds ended during velopharyngeal closure (98/134, 73.1%). For all materials, swallowing sounds did not start when the materials flowed into the pyriform sinuses, and very few sounds corresponded with epiglottic movements. These results show that many movements associated with physiologic events―including hyoid bone and laryngeal excursion, and opening of the upper esophageal sphincter―may be involved in the production of swallowing sounds.