Effect of Temporary Closure of Oronasal Fistula on Levator Veli Palatini Muscle Activity

Aerodynamic variables such as oral air pressure (Goto,1977, Kuehn and Moon,1993), nasal air pressure (Tachimura,1985, Kuehn,1993) and nasal air flow (Tachimura,1992) have been reported to be involved in the regulatory system of velopharyngeal function during speech. Tachimura et al. (1993) clarified that levator veli palatini muscle activity is increased in relation to the flow rate of phonatory air that is emitted from the oral cavity into the nasal cavity through the veloph arynx of normal speakers and patients wearing a well-adapted speech appliance. This implies that nasal air, which is allowed to flow into the nasal cavity through an oronasal fistula, could influence levator muscle activity during speech. The purpose of this study was to examine the effect of temporary closure of an oronasal fistula on levator muscle activity. Five cleft palate patients who received surgery were used as subjects. The subjects were classified into two groups (VPC group and VPI group) according to their velopharyngeal function. Smoothed EMG of the levator muscle and oral air pressure were recorded. Two experiments were performed; In the first (Condition- I) an oronasal fistula was left unclosed so that respiratory air could eacape into the nasal cavity, and in the second (Condition- II), the oronasal fistula was tightly closed by means of packing it with cotton. The subject produced the speech sample /pω/ 20 times in each condition. Oral air pressure increased in association with the temporary closure of an oronasal fistula for all subjects in both groups. There was no significant difference between levator muscle activity in condition- I and that in condition-II for all subjects in the VPI group. However, levator muscle activity in condition- II was significantly smaller than that in condition- I for all subjects in the VPC group (p<0.01; t-test). The results suggested that the oronasal fistula can affect levator muscle activity in patients with adequate velopharyngeal function and nasal air flow may be involved in the regulatory system of velopharyngeal function irrespective of the place where phonatory air escapes into nasal cavity.