The Effect of Sub-glottal Convergence Angle on the Degree of Glottal Closure / 听力学及言语疾病杂志

ABSTRACT

Objective To study the effect of sub-glottal convergence angle on the degree of glottal closure, and to analyze the potential mechanism of dysphonia by the incomplete glottal closure.Methods Three vocal fold positions (adduction, intermediate and abduction) were evaluated by the degree of glottal closure, and divided into three groups.The neck CT images of the subjects were gathered.The vocal folds were adduction group when the normal subjects made a sustaining phonation /i/ during CT scanning;the vocal folds were abduction group when the normal subjects made a deep breathing during CT scanning, and the unilateral vocal folds were incomplete closing group when the unilateral vocal fold paralysis subjects made a deep breathing during CT scanning.3D models of the vocal folds and the airway were reconstructed using Mimics software, through which the sub-glottal convergence angle was measured.Using one-way factor analysis of variance, we compared the angle among three groups.Results The angle changed with degree of glottal closure, with statistically significant differences among the three groups(P<0.01).The means of the angle in three groups were 33.49°±3.75°, 55.03°±2.61° and 75.02°±7.32°.Conclusion The 3D model generation from CT data is an effective method of measuring the sub-glottal convergence angle, while the angle changes with the degree of glottis closure.The angle may affect sub-glottal pressure distribution in the sub-glottal shear or normal direction and influence vocal fold vibration, which would make vibration and vocal fold mucosal wave generation more difficult, and might cause dysphonia.