Defining Normal Sequential Swallowing Biomechanics

Abstract

Little is known about the physiology of a common fluid ingestion pattern-sequential swallowing. This study investigated sequential swallowing biomechanics in healthy adults. Archival normative videofluoroscopic swallow studies were analyzed for hyolaryngeal complex (HLC) patterning and biomechanical measures from the first 2 swallows of a 90-mL thin liquid sequential swallow task. The effects of age, sex, HLC type, and swallow order were explored. Eighty-eight participants were included in the primary analyses as they performed sequential swallows. HLC Type I (airway opens, epiglottis approaches baseline) and Type II (airway remains closed, epiglottis remains inverted) most commonly occurred (47% each), followed by Type III (mixed, 6%). Age was significantly associated with Type II and longer hypopharyngeal transit, total pharyngeal transit (TPT), swallow reaction time (SRT), and duration to maximum hyoid elevation. Males demonstrated significantly greater maximum hyoid displacement (Hmax) and longer duration of maximum hyoid displacement. Significantly larger maximum hyoid-to-larynx approximation was linked to the first swallow, while the subsequent swallow had significantly longer oropharyngeal transit, TPT, and SRT. Secondary analyses included an additional 91 participants who performed a series of discrete swallows for the same swallow task. Type II had significantly greater Hmax than Type I and series of discrete swallows. Sequential swallowing biomechanics differ from discrete swallows, and normal variance exists among healthy adults. In vulnerable populations, sequential swallowing may challenge swallow coordination and airway protection. Normative data allow comparison to dysphagic populations. Systematic efforts are needed to further standardize a definition for sequential swallowing.

Keywords: Biomechanics; Healthy adults; Normal swallowing; Sequential swallowing.

Fig. 1

Hyolaryngeal complex (HLC) Type I. Yellow marker = Tracing of the hyoid/epiglottis. Blue arrow = Open laryngeal vestibule. Red arrow = Closed laryngeal vestibule. Green marker = Tracing of pharyngeal patency. A The rest position frame. B The frame of maximum pharyngeal patency between swallows (less patent than A). C The hyoid position frame during the end of the first swallow. D The HLC is slightly lower than C, the epiglottis is returning to its baseline position, and the laryngeal vestibule is open

Fig. 2

Hyolaryngeal complex (HLC) Type II. Yellow marker = Tracing of the hyoid/epiglottis. Blue arrow = Open laryngeal vestibule. Red arrow = Closed laryngeal vestibule. Green marker = Tracing of pharyngeal patency. A The rest position frame. B The frame of maximum pharyngeal patency between swallows (less patent than A). C The hyoid position frame during the end of the first swallow. D The HLC remains relatively elevated with minor recoil than C, sustained epiglottic inversion, and the laryngeal vestibule is closed

Fig. 3

Hyolaryngeal complex (HLC) Type III. Yellow marker = Tracing of the hyoid/epiglottis. Blue arrow = Open laryngeal vestibule. Red arrow = Closed laryngeal vestibule. Green marker = Tracing of pharyngeal patency. A The rest position frame. B The frame of maximum pharyngeal patency between swallows (less patent than A). C The hyoid position frame during the end of the first swallow. D The HLC is slightly lower than C, sustained epiglottic inversion, and the laryngeal vestibule is open