Determination of Xanthan Gum-Based Thickener Concentration for Videofluoroscopic Contrast Media

The viscosity of liquid care foods is adjusted with a thickener, because suitable thickness prevents aspiration for the patient with dysphagia. Videofluoroscopy is used for detailed investigation of swallowing disorder, where the test liquid of an X-ray contrast medium is thickened to become comparable to the mealtime liquid. The effect of thickeners is influenced by the original viscosity of the contrast medium. Considering this influence, it is important to adjust the thickener concentration for the X-ray test liquid corresponding to the target viscosity. In this study, the effect of thickener concentration on viscosity thickening was investigated for xanthan gum-based thickeners. The viscosity/shear rate curve measured for the aqueous solution was fitted to a Carreau model, and the model constants were formulated as functions of the thickener concentration. Next the modelling method was extended to include the influence of contrast medium viscosity on the thickener concentration effect through the relative viscosity and apparent shear stress. The proposed method made it possible to easily determine the thickener concentration corresponding to the target viscosity for an X-ray test liquid. In addition, the influence of solution density on the syringe flow test was discussed.