Effect of asymmetric vocal fold stiffness on traveling wave velocity in the canine larynx

The vocal fold (VF) traveling wave is essential to normal voice production. The present investigation describes a new method to determine traveling wave velocity (TWV) in the in vivo canine phonatory model. This method synchronizes photoglottographic and electroglottographic waveforms with videostroboscopic images to determine the duration of time the traveling wave moves between two tattoos placed a known distance apart between the upper and lower margins of each VF. Using this method, we compared the TWV of a paralyzed VF with the TWV of the contralateral, electrically stimulated VF during phonation in two canines. In addition, the presumed VF stiffness asymmetry in the simulated acute recurrent laryngeal nerve paralysis state was confirmed by measuring Young's modulus of each VF. The results indicated that the TWV of the paralyzed VF averaged 55% of the TWV of the normal, stiffer VF when the glottal gap was small and entrainment occurred. This study demonstrated the feasibility of quantifying traveling wave motion in asymmetric VF stiffness disorders. The potential use of TWV in human beings as a target to optimize the phonosurgical results in asymmetric VF stiffness disorders is discussed.