Yoshimi Kadota

Vocal fold vibration viewed from the tracheal side in living human beings

The mucosal upheaval where the mucosal wave starts and propagates upward appears on the lower surface of the canine vocal fold during vibration. We investigated the vibratory behavior of the in vivo human vocal fold viewed from the tracheal side. Subjects consisted of 14 men and 6 women who had undergone tracheostomy for various head and neck diseases; their ages ranged from 22 to 70 years, with a mean of 53.9 years. The inferior aspect of the vocal fold during phonation was observed with the aid of a rigid oblique-view endoscope inserted through a tracheostome (inferior glottoscopy). Each subject was asked to sustain the vowel /a/ at a comfortable pitch and loudness (easy phonation) and then at a higher pitch. Inferior glottoscopy could be performed during easy phonation in 19 subjects and during high-pitched phonation in 10 subjects. During easy phonation, the mucosal upheaval appeared on the lower surface of the vocal fold between the anterior commissure and the vocal process in all 19 subjects. During high-pitched phonation, the vocal fold became longer, and the subglottic vault surrounded by the bilateral mucosal upheavals became narrower compared with those during easy phonation. Use of a dilated blood vessel as a landmark in one subject showed the location of the mucosal upheaval on the vocal fold mucosa to actually shift medially toward the oral side during high-pitched phonation. Despite structural differences between the human and canine vocal folds, the infraglottic aspect of the vocal fold vibration observed in the living human larynx was quite similar to that observed in the excised canine larynx (Otolaryngol Head Neck Surg 1996;115:329-34.)

Infraglottic aspect of canine vocal fold vibration: Effect of increase of mean airflow rate and lengthening of vocal fold

The mucosal upheaval (MU), where the mucosal wave starts and propagates upward, appears only when the vocal fold vibrates. The location of the MU histologically and the effect of changes in mean air flow rate (MFR) and vocal fold length on occurrence of the MU were studied in twelve excised canine larynges. The lower surface of the vocal fold was marked to serve as a landmark for subsequent study. Cricothyroid approximation was performed to lengthen the vocal fold. After taking high-speed pictures or recording stroboscopic images from the tracheal side, a small cut wound was made at the mark. This wound served to compare the position of the MU with the histologically identified location of the mark. The larynx was then sectioned in the frontal plane. Before lengthening the vocal fold, the MU occurred on the area where the lamina propria became thinner and where the muscular layer neared the epithelial layer. After lengthening the vocal fold, the MU actually shifted medially compared with its original position. The subglottic area surrounded by the bilateral MUs became longer and thinner. Whether or not complete glottal closure during a vibratory cycle was achieved did not alter these findings. In contrast, with a fixed vocal fold length the MU appeared more laterally as MFR increased, but, based on the relation with the mark, its location on the vocal fold did not change from its original position before increase of MFR.

Quantitative Evaluation of the Effects of Thyroarytenoid Muscle Activity upon Pliability of Vocal Fold Mucosa in an In Vivo Canine Model

Stiffness of the vocal fold is a significant factor in determining mucosal wave propagation and in the control of the fundamental frequency of phonation. We measured pliability of the vocal fold mucosa in an in vivo canine model as an index of stiffness while the histological layer‐by‐layer structure of the vocal fold was not disrupted.

Pliability of Canine Vocal Fold Mucosa in Relation to its Vibration

A novel and clinically practical method of delivering surfactant to the eustachian tube was studied in a gerbil model of OME. OME was induced in 20 gerbils via transtympanic inoculation of heat-killed Streptococcus pneumonia. Twentyfour of forty ears (60%) were successfully inoculated. Inhaled, nebulized surfactant was used to treat the animals with microscopically confirmed OME over a period of 5 days. Eustachian tube opening studies were performed on both affected and nonaffected animals. Successful eustachian tube opening pressures were obtained in 30 of 40 ears (75%). Mean opening pressure for animals without effusion (healthy) was 42.5 mm Hg. Mean opening pressure for animals with effusion treated with nebulized surfactant was 39.4 mm Hg. This pilot study in animals suggests that inhaled, nebulized surfactant may be efficacious in establishing normal eustachian tube function within the clinical picture of OME.

Pliability of the Vocal Fold Mucosa in Relation to the Occurrence of the Mucosal Upheaval

Yoshimi Kadota, Hironobu Kurokawa and Eiji Yumoto Vocal fold vibration has been considered to be a transmission of mucosal waves which move upward from the mucosal upheaval. The mechanism of the occurrence of the mucosal upheaval has not been known yet. The purpose of this study was to relate the pliability of the mucosa to the occurrence of the mucosal upheaval. In addition, a histological basis for the occurrence of the mucosal upheaval was investigated. Five mongrel dogs were used in the experiment. After administration of an intramuscular Ketaral injection, the larynx was excised and divided vertically into two segments (hemilarynges) . Pliability of the vocal fold mucosa was measured at 5-7 points ranging from the free edge to 8 mm below the edge at the middle, anterior forth and posterior forth of the membranous portion. Following the pliability measurements, each hemilarynx was fixed in formalin, sectioned in the frontal plane and stained for histologic examination. Results were summarized as follows : 1) The free edge showed the greatest pliability. The pliability of the mucosa became smaller as the edge became further. The mucosa at 3 mm below the free edge showed the least pliability. 2) The mucosa at the middle of the membranous portion had a greater pliability than that at the anerior and the posterior forth. 3) The lamina propria of the mucosa was thinnest at 3-4 mm below the free edge. At this thinnest point, the muscle layer was closest to the epithelial layer.