Effect of shear thinning on aspiration – Toward making solutions for judging the risk of aspiration

Polysaccharide solutions containing a contrast medium were prepared so that their viscosity at 50 s−1, which was reported as a shear rate in the oral cavity, is the same but different at other shear rates. Preparation procedure of such solutions based on heat treatment using widely used polysaccharides in foods is described, and the rheological properties of these solutions are discussed in relation with flow behaviours in the swallowing process. Videofluorographic observation was performed for healthy persons and patients and compared with rheological characteristics of these solutions to understand the mechanism of aspiration. It was shown that the degree of aspiration depended on the degree of shear thinning of polysaccharide solutions. This study showed the possibility to find what kind of fluid induces the aspiration and to reduce the risk of aspiration in dysphagic patients by controlling the food rheology.