Effects of driving pressure and recurrent laryngeal nerve stimulation on glottic vibration in an in vivo constant pressure model of phonation

Most in vivo studies of phonation have used constant flow models. However, because the lung–thorax system is better viewed as a constant pressure source, a constant pressure in vivo canine model was developed. In this model, driving pressure and recurrent laryngeal nerve (RLN) stimulation are independent variables, and subglottic pressure (Psub; measured immediately under the glottis), air flow, fundamental frequency (F0), and glottic area are dependent variables. In three dogs, Psub and air flow were measured with constant RLN stimulation and varying driving pressure, and in another condition with constant driving pressure and varying RLN stimulation. Videostroboscopic measures on four animals assessed glottic areas with constant RLN stimulation and varying driving pressure. With constant RLN stimulation, increasing driving pressure had no effect on glottic area, while F0, and air flow increased significantly. Changes in Psub were small in comparison to changes in driving pressure. With constant driving pressure, increasing RLN stimulation increased Psub and F0 and decreased air flow. These findings suggest that Psub during phonation is primarily dependent on RLN activity and associated laryngeal muscular contraction, but not on lung driving pressure. [Work supported by VA Merit Review funds.]