Unilateral vocal fold paralysis (UVFP) can present with structural asymmetries in left-right position of the membranous folds, vocal fold height, length, tension, and arytenoid position. Surgically there is often controversy on how to restore optimal vocal function. Work in our previous R01 showed vortices form in the superior aspect of the divergent glottis during closing, and are associated with changes in the flow rate such as greater flow skewing (previously thought to be only caused by increased vocal tract inertance), and with favorable effects on loudness and intelligibility. Thus we hypothesize a better understanding of these vortices, and their effect on flow rate and acoustics, will open up a new paradigm to evaluate and design new surgical interventions for unilateral paralysis and other conditions featuring structural asymmetries. So far our findings are based on two-dimensional (2D) measurements whereas intraglottal geometry and flow rate change in all three-dimensions (3D). The extention of our technique from 2D to 3D will allow completion of the following specific aims:
Specific Aim 1. Using a combination of computational and excised canine larynx models, characterize the effects of vocal tract inertance, intraglottal vortices and tissue elasticity on te medial surface dynamics of the folds, volumetric flow rate at the glottal exit, and acoustics in th following models: 1A. Excised canine larynx with relative symmetry in vocal fold length, height, and stiffness. 1B. Excised canine larynx with asymmetries in vocal fold length, height, and stiffness. 1C. Excised canine larynges that have a Thyroplasty Type I with various implant shapes and degrees of infraglottal medialization. 1D. Excised canine larynges that have Thyroplasty Type I with and without arytenoid adduction.
Specific Aim 2. Volumetric flow rate will be measured directly at the glottal exit using volumetric particle imaging velocimetry and indirectly at the mouth using inverse filtering in an excised canine larynx model with a mechanical vocal tract.
There is currently no consensus on optimal treatment for unilateral vocal fold paralysis; one main reason for this is a lack of understanding of the underlying mechanisms of how structural asymmetries found in unilateral paralysis, and the surgical treatments designed to correct these asymmetries, affect voice production. This proposal will elucidate these mechanisms using innovative methodology.
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