2012 Volume 16 Issue 3 Pages 283-289
[Purpose] Closure of the lips is critical for the normal swallowing process. However, it is unclear how swallowing dynamics are altered when food is swallowed with the lips open. This study examines the optimal volume for a swallow of water as a preliminary study of lip status-dependent changes of swallowing dynamics. Furthermore, when the thing was inserted between lips also in the time of lips opening, it aimed at investigating whether the same optimal volume for a swallow as the time of lips closing can be obtained.
[Subjects and Methods] Subjects were 22 healthy adults without swallowing disorder (12 males and 10 females; mean age, 21.9±2.7 years). While in a supine position with the head in a mid-position, subjects’ lips were parted in 4 ways in a random order: 1) close, 2) open minimally with a piece dental cotton roll placed horizontally between the lips, 3) open largely with a piece of dental cotton roll placed vertically between the lips, and 4) following an instruction that the lips were parted voluntarily approximately 1 cm without the use of a piece of dental cotton roll. Subjects were instructed to mimic a swallowing action, and then an examiner poured 10 ml of water onto the bottom of the oral cavity using a syringe. The subjects were instructed to drink the water of the quantity which can be drunk comfortably at once. The remaining water was flushed from the mouth into a paper cup, which was weighed on an electronic scale. Accordingly, the volume of swallowed water or the optimal volume for a swallow was calculated by subtraction.
[Results] The optimal volume for a swallow was 9.38±1.75 ml with the lips closed, 9.39±1.87 ml with the lips opened minimally using a cotton roll, 9.28±1.73 ml with the lips opened largely using a cotton roll, and 8.59±2.13 ml with the lips parted voluntarily.
[Conclusions] The optimal volume for a swallow was decreased when the lips were parted voluntarily without a cotton roll (p＜0.01). However, if a piece of cotton roll was placed between the parted lips, the volume was restored to that obtained when the lips were closed.
