Pressure profiles on the walls of the glottis for oblique glottal ducts

Abstract

Oblique angles of the glottis occur during both normal and abnormal phonation. This study examined pressures on the glottal walls for a variety of oblique angle conditions. A Plexiglas model of the larynx was used to obtain wall pressures at 14 taps along the glottal surfaces. The model is 7.5 times larger than real life. A minimal diameter of 0.04 cm and duct axial length of 0.3 cm were used for all cases. Results indicated, for example, that for an included angle of 10 deg (divergence) and a transglottal pressure of 5-cm H2O, an oblique glottal angle of 15 deg compared to the symmetric glottis: (1) displaced the minimal wall pressure location on the divergent side a short distance downstream and on the convergent side to mid-glottis; (2) increased the pressure drop on the divergent side by about 15% and decreased the pressure drop on the convergent side by about 13%; and (3) broadened the minimum pressure dip on both the divergent and convergent sides. These results suggest paradoxical (opposite) driving pressures on the inferior glottal walls, which would enhance the nontypical phase differences between the two vocal folds. [Research support: NIH grant 1R01DC03577.]