Simultaneous Kinetic Analysis of Lip and Tongue During Swallowing

―Examination With CCD Camera and Ultrasound Sonography―

Abstract

Lips play a very important role in the oral stage， and their functions should be carefully observed． At present， however， few researchers have conducted studies of lip movement from the standpoint of feeding and swallowing functions． Although direct observation has conventionally been regarded as difficult， in this study we tried to observe the dynamic relationship between the tongue， which is a crucial element in the oral stage of swallowing， and lips during swallowing． The subjects studied included 29 healthy adult volunteers． A high-resolution CCD camera was used to study the lip movement and ultrasound sonography was used to study the tongue movement． The data obtained on the same time axis were evaluated quantitatively and qualitatively by two-dimensional dynamic analysis． The results were summarized as follows．

1． The outward traction of the angles of the mouth definitely preceded the elevation of the dorsum of tongue toward the palate． Therefore， the start time of lip movement （LS）was regarded as the common reference point for lip and tongue movement， and the movement changes were carefully observed over the course of time．

2． According to the measurement results of the width of lips during the swallowing period， the average difference between the start of lip movement and LP was 5.6 mm． The existence of a significant difference between the width of lips measured at the beginning of lip movement and that measured at the time of LP and the fact that the average difference accounted for 23.5％ of the horizontal range of lip movement suggested that showed the traction of the angles of the mouth was generally due to swallowing， even in healthy adults．

3． The time required for swallowing using the lip and tongue movement was 2.56 seconds on the average．

4． Because the start of lip movement was used as a reference point in the present study， there was variance in the measurements of other various items． ln spite of these significant individual differences， the mean individual coefficients of variation were small．The lip and tongue movement suggests that healthy adults probably have their own individual mechanism of swallowing．

5． The results of the present study suggested that swallowing movement consisted of the following processes： the initiation of vigorous outward traction of the angles of the mouth after mastication， the acceleration of the elevation of the tongue toward the palate， and the transportation of bolus to the pharynx．

The careful observation of the lip movement enabled us not only to define the initiation of swallowing， but also to dynamically study the tongue movement．