Initiation of Pharyngeal Response during Discrete Swallowing and Chew-swallowing in Healthy Subjects.

Abstract

The aim of this study was to measure the initiation of pharyngeal swallowing during discrete swallowing and during chew-swallowing in younger and older healthy subjects and to determine the normal range of the stage transition duration (STD) for different food boluses. The correlations between STDs were investigated. Twenty-eight younger subjects (< 60 years old) and 25 older subjects (≥ 60 years old) were enrolled. While in the sitting position, the subjects swallowed 10 ml of thin liquid barium (LQ), 8 g of corned beef hash with barium (CB), 8 g of cookie with barium (CK), and a two-phase mixture of 4 g of corned beef hash with barium and 5 ml of thin liquid barium (MX). A videofluoroscopic examination of swallowing was performed at 30 frames/s in the lateral projection. The delay in pharyngeal swallowing (i.e., STD) was measured. The normal range (mean ± 2SD) of STDs for each bolus type was determined, and correlations were calculated to examine the relationship among STDs. The median STDs for LQ, CB, CK, and MX in all subjects were 0.0, 1.2, 2.4, and 1.9 s, respectively. The STDs were prolonged for CB, CK, and MX compared with LQ. Additionally, the median STD was longer for LQ, CB, and CK in older than in younger subjects. No significant correlations were found between STDs except for those between CB and CK. A delayed pharyngeal response is commonly observed during chew-swallowing. Liquids, solids, and two-phase mixtures exhibit independent timings of pharyngeal swallow initiation.