Effect of Difference in Viscosity between Liquids with Low-Viscosity on Levator Veli Palatini Muscle Activity during Swallowing

Abstract

Purpose: The transition between the oral and pharyngeal phases is one of the times when mis-swallowing of a low-viscosity liquid like water occurs. Adequate regulation of the velopharyngeal value for swallowing, in which the velum is primarily involved, is essential for preventing aspiration of the airway. The purpose of this study was to examine electromyographically whether differences in the viscosity of low-viscosity liquids could influence regulation of the velopharyngeal valve with levator veli palatini (LVP) muscle activity.

Method: Ten healthy subjects (age: 21–32, average age: 24.0, SD: 2.9) without any clinical history of dysphagia were enrolled in this study. Smoothed EMG signals of the LVP muscle were collected. Each subject swallowed water and milk of a certain volume 10 times. The swallowing volume was individually determined on the basis of the optimum volume for swallowing for each subject.

Result: LVP muscle activity was significantly smaller for milk than for water for seven of the ten subjects (paired t-test, p＜0.01). As a group, EMG activity was also significantly greater for water than for milk.

Conclusion: It was clarified that velopharyngeal function for swallowing depended on the viscosity for liquids having a viscosity close to that of water.