Effect of body position on tongue movement during swallowing

Abstract

In patients with feeding/swallowing disorders, adjustment of posture is a very effective means of preventing aspiration. A posteriorly flexed rather than vertical trunk position is widely known to be a safe body position in which aspiration is less likely to occur. Therefore, in patients at high risk of aspiration, the trunk and neck angles are adjusted clinically in various situations. Regarding the relationship between posture adjustment and swallowing dynamics, although there have been a number of evaluations in the pharyngeal and esophageal phases, few detailed evaluations have been made in the oral phase despite its importance. Physiologic evidence is considered to be insufficient in this area. In this study, the effects of posture adjustment on tongue dynamics in the oral phase were evaluated by measuring the tongue pressure on the palate using touch sensors.
The subjects were 7 healthy dentulous individuals who had no feeding/swallowing disorder with a mean age of 26 years. The test food was water at 37 C. Swallowing volume was determined by having each subject swallow water 10 times consecutively and calculating the mean volume of a single gulp, which was found to be 7.9±1.4 mL. The test maneuver was a single gulp on instruction of the examiner. Swallowing was performed in a total of 6 body positions, i.e., at trunk angles of 90°, 60° and 30° relative to the floor, and with neck angles of neutral and anteriorly flexed/protruded positions at each trunk angle. Sensors were attached using the denture stabilizer Touch Correct II (Shionogi, Osaka, Japan) as follows: Sensor 1 was placed at the point of intersection between the line connecting the basal tubercles of the bilateral upper canine teeth and median line, Sensor 2 at the intersection between the line connecting the distal palatal cusps of the bilateral second upper molars and the median line, and the center of Sensor 3 immediately below the palatal neck of the left upper second molar on the line connecting the distal palatal cusps of the bilateral upper second molars.
In the neutral neck position, all sensors indicated significant shortening of the duration of tongue pressure with increases in the angle of trunk flexion. In Sensors 1 and 3, the maximum tongue pressure decreased with increases in the angle of trunk flexion. In the anteriorly flexed/protruded neck position, no shortening of the duration of tongue pressure or decrease in the maximum tongue pressure associated with trunk flexion was noted. Changing the neck angle from the neutral to anteriorly flexed/protruded position seemed to compensate for the decrease in the maximum tongue pressure and the tongue pressure duration.