Effects of Angle of Epiglottis on Aerodynamic and Acoustic Parameters in Excised Canine Larynges.

OBJECTIVES: The aim of this study is to explore the effects of the angle of epiglottis (Aepi) on phonation and resonance in excised canine larynges. METHODS: The anatomic Aepi was measured for 14 excised canine larynges as a control. Then, the Aepis were manually adjusted to 60° and 90° in each larynx. Aerodynamic and acoustic parameters, including mean flow rate, sound pressure level, jitter, shimmer, fundamental frequency (F0), and formants (F1'-F4'), were measured with a subglottal pressure of 1.5 kPa. Simple linear regression analysis between acoustic and aerodynamic parameters and the Aepi of the control was performed, and an analysis of variance comparing the acoustic and aerodynamic parameters of the three treatments was carried out. RESULTS: The results of the study are as follows: (1) the larynges with larger anatomic Aepi had significantly lower jitter, shimmer, formant 1, and formant 2; (2) phonation threshold flow was significantly different for the three treatments; and (3) mean flow rate and sound pressure level were significantly different between the 60° and the 90° treatments of the 14 larynges. CONCLUSIONS: The Aepi was proposed for the first time in this study. The Aepi plays an important role in phonation and resonance of excised canine larynges.

Evaluation of Surgical Strategies for Bilateral Vocal Fold Paralysis Using Excised Canine Larynges.

OBJECTIVE: The objective of this study was to provide a theoretical basis for the selection of optimal surgical procedures in ex vivo simulated bilateral vocal fold paralysis (BVFP). STUDY DESIGN: Four surgical stages were sequentially performed on 10 excised canine larynges with simulated BVFP: (1) transverse cordotomy, (2) medial arytenoidectomy, (3) subtotal arytenoidectomy, and (4) total arytenoidectomy. MATERIALS AND METHODS: The sound pressure level, the signal-to-noise ratio, the glottal resistance, the glottal airflow (GF), the maximal glottal area (MGA), and spectrograms were measured after each stage. For comparative analysis of variance, a randomized block design and the Student-Newman-Keuls test were performed. RESULTS: Under stable phonation, the sound pressure level showed no significant differences among the four stages. The signal-to-noise ratio was significantly different between the preoperative period and stage 1, as well as between stages 2 and 3. Glottal resistance was significantly different between the preoperative period and stage 1 and between stages 1 and 2. GF and MGA were significantly different among all stages, compared with those between stages 3 and 4 for GF and the preoperative period and stage 1 for MGA. The spectrograms indicated that the degree of disorder in the acoustic signals gradually increased. CONCLUSIONS: Based on a comprehensive analysis of GF and voice quality in excised canine larynges, which simulated BVFP, our results suggest that the optimal surgical choice for BVFP is either medial or subtotal arytenoidectomy.