Dynamic glottal pressures in an excised hemilarynx model

During phonation, air pressures act upon the vocal folds to help maintain t heir oscillation. The air pressures vary dynamically along the medial surfa ce of the vocal folds, although no live human or excised studies have shown how those pressure profiles vary in time. The purpose of this study was to examine time-dependent glottal pressure profiles using a canine hemilarynx approach. The larynx tissue was cut in the midsaggital plane from the top to about 5 mm below the vocal folds. The right half was replaced with a Ple xiglas pane with imbedded pressure taps. Simultaneous recordings were made of glottal pressure signals, subglottal pressure, particle velocity, and av erage airflow at various levels of adduction. The data indicate that the pr essures in the glottis (on the Plexiglas) vary both vertically and longitud inally throughout the phonatory cycle. Pressures vary most widely near the location of maximum vibratory amplitude, and can include negative pressures during a portion of the cycle. Pressures anterior and posterior to the max imum amplitude location may have less variation and may remain positive thr oughout the cycle, giving rise to a new concept called dynamic bidirectiona l pressure gradients in the glottis. This is an important concept that may relate strongly to tissue health as well as basic oscillatory mechanics.