The resistance and the efficiency of the glottis as the generator of voice production are important factors, but it has been impossible to measure them, because we have no practical measuring method of the subglottic pressure except in the patients with a tracheostoma.
The intention of this paper is to offer the measuring method of the subglottic pressure in normal persons and to develop the investigation of the regulation mechanism of voice.
The relation between the intraesophageal pressure and the subglottic pressure was examined and a new interruption method was tried.
The change of the intraesophageal pressure during the phonation has a close relation with the expiratory level and it is not parallel with subglottic pressure. But both pressures have equal deviations and synchronized changes only in the beginning or the stopping of voice. Van den Berg's intraesophageal method-measuring the pressure deviation at the abrupt stop of voice, with the relaxed diaphragm and thorax and the open glottis-is certified as an almost accurate method. In this method, it is not always easy to swallow the esophageal balloon, and the complicated technique is required.
The interruption method-at first devised to measure the alveolar pressure in the respiration- was examined.
The examiner let the subject put on a mask, which is airtight and connected with shutter and pneumotachograph. During the phonation, the pressure elevation was produced in the mask by the momentary interruption of the air-flow by means of the shutter. This pressure elevation was equal to the subglottic pressure. This fact was ascertained in the patient with a tracheostoma and the interruption of air-flow gave little effect to the subglottic pressure. This method was painless and easily performed.
As is stated, we have two methods concerning the measurement of the subglottic pressure. The interruption method is better for the measurement of the resistance and the efficiency of voice production, and the intraesophageal method is better for the observation of the changes of subglottic pressure in the beginning of phonation or in the production of consonants in which the change of the expiratory level is little.
