Comparing Phonation Threshold Flow and Pressure by Abducting Excised Larynges

Abstract

This experiment studied a new aerodynamic parameter, phonation threshold flow, along with phonation threshold pressure, by varying prephonatory glottal width in canine larynges ex vivo. Goals were to examine phonation threshold flow as a measurable parameter sensitive to physiologic changes in the vocal folds and compare the relative sensitivities of phonation threshold flow and phonation threshold pressure. Ten excised canine larynges were tested on a bench apparatus for subglottal pressure and airflow at phonation onset. Metal shims simulated abduction levels ranging from 0.0 to 4.0 mm. For each glottal configuration, airflow through the larynx was increased until the vocal folds began vibrating, and onset airflow and pressures were recorded. One-way analysis of variance (ANOVA) found significant differences in the aggregate phonation threshold flow means over the latter portion of the width domain (1.0-4.0 mm). Phonation threshold flow increased as posterior glottal width increased and was modeled linearly. One-way ANOVA of phonation threshold pressure means was insignificant, with a P value of .941. Results showed phonation threshold flow to be more sensitive to posterior glottal width changes than phonation threshold pressure. Therefore, phonation threshold flow could be a more effective indicator than phonation threshold pressure for those vocal diseases related to abduction.