Relationship between Flow Properties of Thickener Solutions and Their Velocity through the Pharynx Measured by the Ultrasonic Pulse Doppler Method

Abstract

The effect of viscosity µ of thickener solutions on their velocity through the human pharynx measured using the ultrasonic pulse Doppler method was investigated to develop an index for thickener solutions used as foods for dysphagic patients. The B-type viscometer determined an approximated value of viscosity at a selected shear rate γ. The maximum velocity V_max of water, which is often aspirated into trachea of patients with dysphagia, was about 3 times higher than that of yogurt, which is rarely aspirated. Moreover, the velocity spectra for water and thickener solutions of low concentration tended to be distributed over a wider range than those of yogurt and thickener solutions of high concentration. The maximum velocity V_max of the thickener solutions approached that of yogurt as concentration increased. The maximum velocity V_max correlated well with µ; the correlation coefficient at the shear rate of 10 s^-1 was somewhat larger than those at the shear rate of 1 s^-1 and 100 s^-1.