Effect of Nasal Air Flow Rate and Oral Air Pressure on Levator Veli Palatini Muscle Activity in Normal Speakers

Abstract

Tachimura et al. (1995) have suggestedt hat levator veli palatini m uscle (LVP) activity is increased in relation to flow rate of air emitted from the oral cavity into the nasal cavity through the velopharynx of postoperativec left palate patients wearing well-adapteds peech aid. However, it has not clarified whether or not nasal air flow is involved in the regulatory system of LVP activity of normal speakers. The purpose of this study was to clarify the effect in the non-cleft normal speakers and to test the hypothesis that nasal air flow is an important factor in the regulatory system of LVP activity of normal speakers.
Five non-clef tn ormal speakers were selected as experimentals ubject. s To introduce phonatory air to the nasal cavity during phonation, a hollow tube with an aperture (φ5 mm) on its side was devised and inserted through the nostril to the velopharynx. Smoothed electromyogram of LVP, oral air pressure and nasal air flow were recorded. Two experiments were performed: In the first (Condition-1), the inner cavity of the tube inserted into the velopharynx was occluded thereby avoiding nasal air emission and in the second (Condition-2), phonatory air was introduced to the nasal cavity by means of reopening the inner cavity of the tube. The subjects pronounced the /pu/ more than 20 times in each condition.
LVP activity in the condition of emergence of nasal air flow (Condition-2) was significantly greater than ( P <0.05; t-test) that in the condition of no introduction of air to the nasal cavity (Condition-1). Multiple regression analyses based on LVP activity as a criterion variable and oral air pressure and nasal air flow rate as explanatory variables revealed that nasal air flow may influence LVP activity more dominantly than oral air pressure. It was concluded that nasal air flow is involved in the regulatory system of LVP activity of normal speakers.