Function of the posterior cricoarytenoid muscle in phonation: in vivo laryngeal model.

The function of the posterior cricoarytenoid (PCA) muscle in phonation has not been well documented. To date, several electromyographic studies have suggested that the PCA muscle is not simply an abductor of the vocal folds, but also functions in phonation. This study used an in vivo canine laryngeal model to study the function of the PCA muscle. Subglottic pressure and electroglottographic, photoglottographic, and acoustic waveforms were gathered from five adult mongrel dogs under varying conditions of nerve stimulation. Subglottic pressure, fundamental frequency, sound intensity, and vocal efficiency decreased with increasing stimulation of the posterior branch of the recurrent laryngeal nerve. These results suggest that the PCA muscle not only acts to brace the larynx against the anterior pull of the adductor and cricothyroid muscles, but also functions inhibitorily in phonation by controlling the phonatory glottal width.