Validation of the Normalized Laryngeal Constriction Ratio in Normal and Disordered Swallowing

PURPOSE: The timing of laryngeal vestibule closure (LVC) is important for airway protection during swallowing. However, it is unknown whether the extent of LVC contributes to airway protection. The goal of this study is to validate the extent of LVC via a measure called laryngeal constriction ratio (LCR). METHODS: A retrospective analysis of videofluoroscopic swallows was conducted on 38 stroke participants and 40 healthy controls. The LCR was calculated by deriving a size-normalized area of airspace from a 1) maximum closed laryngeal vestibule and a 2) maximum open laryngeal airspace (at rest). Airway invasion severity was derived via the Penetration-Aspiration Scale score. RESULTS: Six hundred forty-nine videofluoroscopic swallows were analyzed. A mixed model analysis revealed a statistically significant mean difference between the normalized laryngeal constriction ratios of healthy individuals (mean (m) = 0.003) versus older dysphagic patients (m = .026) (P = 0.001), quantifying less closure in older patients with dysphagia. Additionally, swallows with airway compromise had a statistically worse LCR when compared to swallows without airway compromise (P = 0.001). CONCLUSION: The normalized LCR might be a valid fluoroscopic surrogate measure for LVC and, furthermore, airway compromise during swallowing. By investigating spatial measurements in the laryngeal vestibule during safe and unsafe swallows, the LCR provides a direction for further research to allow for critical examination of the physiology relating to closure degree in order to precisely detect and treat abnormalities during swallowing. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:E190-E198, 2020.