Development of Therapeutic Procedure to Stimulate Velopharyngeal Function using Newly Designed Speech Appliance.

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The purpose of this study is to establish a strategy to stimulate velopharyngeal function using speech bulb reduction. To determine an adequate reduction volume of the bulb, levator muscle activity associated with changes in nasal air flow rate and oral air pressure was monitored when respiratory air was allowed into the nasal cavity through the opening drilled in the vertical center of the bulb of a speech appliance. The opening area was varied from 0 (occluded condition) to 38.5mm^2 through 12.6mm^2. Multiple regression analyzes showed that levator muscle activity correlated with nasal air flow rate and oral air pressure, while nasal air flow rate contributed to the changes in levator muscle activity more significantly than oral air pressure did. Based on the results, prototype strategy of bulb reduction therapy was designed and applied to 5 repaired cleft palate patients who were routinely wearing a speech appliance. That is, bulb reduction was performed so that decrease in the bulb volume could be equal to the circular area ranged from 12.6mm^2 to 38.5mm^2 in horizontal projection. The reduction was carried out monthly for 3 months. Nasopharyngeal fiberscopic and perceptual evaluations were carried out onemonth after each reduction. As results, four out of five subjects showed complete closure of the velopharynx and no nasal emission during obstruent speech, and the improved veloharyngeal function was observed in each evaluation. However, another subject showed complete closure in first and second evaluation, while third evaluation did not show any improvement. The results suggested that this prototype of bulb reduction strategy might be effective for the improvement of velopharyngeal function, while the process towards improved velopharyngeal function might be variable across subjects. A maintenance of the reduction effect warrants future study.