EFFECTS OF DRIVING PRESSURE AND RECURRENT LARYNGEAL NERVE-STIMULATIONON GLOTTIC VIBRATION IN A CONSTANT-PRESSURE MODEL

Glottic phonatory parameters have been studied in constant flow models ; however, the lung-thorax system is better viewed as a constant press ure source, Adjusting the driving pressure and recurrent laryngeal ner ve stimulation as independent variables, rather than as dependent vari ables, may provide a more physiologic understanding of laryngeal funct ion and glottic parameters, including subglottic pressure, airflow, fu ndamental frequency, and glottic area. In three dogs subglottic pressu re and airflow were measured in two separate conditions: with constant recurrent laryngeal nerve stimulation and varying driving pressure, a nd with constant driving pressure and varying recurrent laryngeal nerv e stimulation. Videostroboscopic measures on four dogs assessed glotti c areas with constant recurrent laryngeal nerve stimulation at differe nt driving pressures. With constant recurrent laryngeal nerve stimulat ion, increasing driving pressure had no effect on glottic areas, where as subglottic pressure, fundamental frequency, and airflow increased s ignificantly. However, changes in subglottic pressure were minimal in comparison with changes in driving pressure. At constant driving press ure, increasing recurrent laryngeal nerve stimulation increased subglo ttic pressure and fundamental frequency and decreased airflow, These f indings suggest that during phonation subglottic pressure is primarily dependent on recurrent laryngeal nerve stimulation and laryngeal musc ular contraction, but not on lung driving pressure.