[Mechanism of neoglottic adjustment for voice variation in tracheoesophageal speech]

Over the past 17 years, we have been performing tracheoesophageal (TE) fistulization for voice restoration following total laryngectomy. The purpose of this technique is to divert the exhaled air through the TE fistula into the hypopharynx where the inferior constrictor muscle forms the retropharyngeal prominence on which the neoglottis is located. It is generally accepted that both pulmonary power and laryngeal adjustment control voice frequency and intensity change in laryngeal phonation. Regularity at various pitches and voice intensities was seen in TE phonation, despite laryngeal adjustment being lost. Regular voice production with various pitches and intensities requires a regulatory mechanism for both pulmonary power and the neoglottis. This study was designed to clarify the mechanism of neoglottic adjustment in TE phonation. Ten speakers with TE fistula were subjected to aerodynamic and electrophysiological investigations. Tracheal pressure, fundamental frequency, intensity, and airflow rate were measured for easy phonation, a high-pitched voice, and a loud voice. Resistance and efficiency of the neoglottis were calculated from the data obtained. Electromyograms of the inferior constrictor muscle and tracheal pressure were simultaneously recorded when the pitch or intensity of the voice increased. Six of the ten subjects examined were able to produce a high-pitched voice. Tracheal pressure increased in all six, the airflow rate in four, and neoglottal resistance in five, as compared with the data obtained during easy phonation. Nine of the ten subjects examined were able to produce a loud voice. In all nine, both tracheal pressure and the airflow rate increased as compared with the values measured during easy phonation. Neoglottal resistance had no definite pattern in relation to voice intensity changes. Electrophysiological study demonstrated that the activity of the inferior constrictor muscle increased as tracheal pressure increased so as to raise the pitch or increase the intensity of the voice. These results indicate that the adjustment of neoglottic closure and stiffness produced by the inferior constrictor muscle has the role of varying the frequency or intensity of the voice.