[High speed cinematographic analysis of subglottal mucosal vibration during experimentally induced phonation in excised larynges].

Twenty-seven excised canine larynges and two excised human larynges fixed on a wall of a specially constructed glass box, were blown on and the subglottal mucosal vibrations were photographed using high speed cinematography from the tracheal side. Each film was repeatedly projected at normal speed and analyzed frame by frame. Mucosal upheaval appeared between the anterior commissure and the vocal process. The mucosal wave or "traveling wave" started from the mucosal upheaval and propagated medially and upward. The mucosal upheaval vibrated with a small amplitude and with an earlier phase than any other portion of the vocal fold. Increase of air flow resulted in increased amplitude of the free edge excursion. The mucosal upheaval seemed to shift more laterally after the increase of air flow. But judging from the positional relations between the mucosal upheaval and markers, the origin of the mucosal upheaval was the same despite the increase of air flow. After the increase of vocal fold tension by cricothyroid approximation, the mucosal wave occurred within the limited area near the vocal edge. The mucosal upheaval was located more medially as compared to the original position. The mucosal upheaval appeared on what was actually the superior portion of the vocal fold. Direct electrical stimulation of the thyroarytenoid muscle (TA) bulged the lower surface of the vocal fold medially, and narrowed the subglottic area surrounded by bilateral mucosal upheavals during vibration. The mucosal upheaval seemed to shift more medially after stimulation of TA, but combined with the movements of the marker, the mucosal upheaval appeared on a more inferior portion of the vocal fold compared to its position before the stimulation. Thus, a more dynamic mucosal wave appeared in the vertical direction. Histological examination revealed that the mucosal upheaval arose on the lower surface of the vocal fold, slightly above the area where the muscular layer came close to the epithelial layer. After the cricothyroid approximation, the mucosal upheaval occurred in a more upward area where the lamina propria was thicker. In addition, after stimulation of the TA, the mucosal upheaval was located in the area where the muscular layer was thick under the epithelial layer.