TAKEDA Seiko, SAITOH Eiichi, MATSUO Koichiro, BABA Mikoto, FUJII Wataru, PALMER Jeffery B
The Japanese Journal of Rehabilitation Medicine, 39(6) 322-330, Jun, 2002 Peer-reviewed
When normal subjects eat solid food, the bolus is formed in the oropharynx prior to swallowing. Bolus formation for liquids, however, is usually in the mouth. The purpose of this study was to determine whether the act of chewing alters the relationship between bolus position and swallow initiation. Ten healthy volunteers aged 29.2±4.1 years were imaged with videofluorography while consuming barium-mixed foods included 10ml-liquid (LQD), 8g-corned beef hash (CBH), 8g-cookie (COK), and a mixture of 5ml-liquid with 4g-CBH (MIX). They were instructed to chew and then swallow. For liquid, an additional recording was made with command swallow. Swallow onset was defined as the moment hyoid began its rapid elevation. The position of the leading edge of bolus at swallow onset and the duration of bolus transition were measured. The position of the leading edge of bolus was classified in Oral cavity (OC), Upper-oropharynx (UOP), Valleculae (VAL), or Hypopharynx (HYP). With LQD, the leading edge of bolus was in OC or UOP at time of swallow onset in 89.5% of swallows without chewing. In contrast, bolus entered VAL and HYP before swallow onset in 45% of swallows of LQD with chewing. For CBH and COK, the leading edge of the bolus entered VAL before swallow onset in 55.0% and 50.0% of swallows, respectively. For MIX swallows, the leading edge reached VAL or lower before swallow onset in 100% of swallows. From these findings the act of chewing seemed to be a prime determinant of a manner of chew-swallow complex characterized by the existence of the stage II transport. And for observation of this phenomenon clinically, MIX chew-swallowing is the most suitable because of its high reliability. In chew-swallow of food including liquid properties (LQD and MIX), high frequency of bolus entering in HYP before swallow onset was observed. The food transport to hypopharynx seemed to be influenced by gravity. This finding was very important in consideration of aspiration mechanism of dysphagic patients especially with falsenegative results of videofluorographic study. High correlation was recognized in the chewing time and the oropharyngeal transport time, and hypopharyngeal transit time was long in LQD with chewing and MIX. Steadiness of hyoid bone movement time indicated that this parameter should be suitable for standardize of time measurement. The manner of chew-swallow complex was obviously different from that of command swallow. It seemed to be important clinically to assess chew-swallow complex additionally to the conventional videofluorography.