A Detailed Motion Analysis of the Angular Velocity Between the Vocal Folds During Throat Clearing Using High-speed Digital Imaging

Summary Objectives To assess the angular velocity between the vocal folds just before the compression phase of throat clearing (TC) using high-speed digital imaging (HSDI) of the larynx. Methods Twenty normal healthy adults (13 males and seven females) were enrolled in the study. Each participant underwent transnasal laryngo-fiberscopy, and was asked to perform weak/strong TC followed by a comfortable, sustained vowel phonation while recording an HSDI movie (4000 frames/s) of the larynx. Using a motion analysis, the changes in the vocal fold angle and angular velocity during vocal fold adduction were assessed. Subsequently, we calculated the average angular velocities in the ranges of 100–80%, 80–20%, and 20–0% from all of the angular changes. Results The motion analysis demonstrated that the changes in the angular velocity resulted in polynomial-like and sigmoid curves during TC and vowel phonation, respectively. The angular velocities during weak TC were significantly higher in the 20–0%, 80–20%, and 100–80% regions (in order); the 80–20% angular velocity in vocal fold adduction during phonation was highest. The 20–0% angular velocity during strong TC was more than twofold higher than 20–0% angular velocity during phonation. Conclusions The present results confirmed that the closing motions of the vocal folds accelerate throughout the precompression closing phase of a TC episode, and decelerate just before the impact between the vocal folds at the onset of phonation, suggesting that the vocal fold velocity generated by TC is sufficient to damage the laryngeal tissues.