Phonetic effects of Nasal Speaking Valve on experimental velopharyngeal incompetence

Objectives: Velopharyngeal incompetence (VPI) is a contributing factor to speech disorders, frequently accompanying disorders, such as cleft palate, congenital paralysis of the soft palate, and cerebrovascular disease. Dental approach utilizing palatal lift prosthesis (PLP) has been reported to play an important role for the rehabilitation of this kind of speech disorders. PLP has been used to lift soft palate mechanically to enhance the velopharyngeal function. While a well-adjusted PLP would result in satisfactory patient acceptance, patients sometimes have difficulty with appropriate adjustment for becoming accustomed to using the prosthesis. In addition, as the PLP requires sufficient retention to the dental arch or palate, constructing a PLP for edentulous patients can be difficult or even impossible. We have developed a new device, nasal speaking valve (NSV), for these patients. The NSV is a removable device inserted in the nostrils with a custom-made hard outer shell structure. One-way valves inhibiting exhalation through the valve and enabling free inhalation are inside. The NSV could easily be worn and provided for edentulous patients. This study aimed to clarify the effect of the NSV according to the manner of articulation. Methods: Seven healthy volunteers participated in this study. The NSV was made for each subject. Infiltration anesthesia was conducted to the subjects to experimentally induce VPI. The sound data were recorded under the anesthetic condition without wearing NSV (ANE) and with wearing NSV (ANE+NSV). Results: Intelligibility score improved from 48%, in the ANE condition, to 84%, in the ANE+NSV condition. According to the manner of articulation, speech intelligibility in plosive, affricates, approximant and flaps were remarkably improved. Nasals and fricatives did not significantly improved by the NSV. Conclusion: The NSV was effective for dysarthria under experimental VPI condition, especially for the sound which needs high exhalation pressure in oral cavity.