Thickened Liquids for Children and Adults with Oropharyngeal Dysphagia: the Complexity of Rheological Considerations

Abstract

Dysphagia clinicians use thickened liquids in the medical management of oropharyngeal dysphagia across the age span. Mixing instructions to create thickened liquids are deceptively simple, suggesting these products are as easy and reliable to make as a cup of tea. Research has shown, however, that thickened liquids are anything but a homogenous commodity. Although thickness or viscosity is often the focus of measurement, other material property characteristics of the internal structure of the liquid, such as density and yield stress, affect the way that thickened liquids move and behave. This paper discusses the structural or rheological properties of thickened liquids and thickening agents. It describes the effects of thickening agents on mouthfeel and flavor release, both of which contribute to compliance with a prescription for all liquids to be consumed in a thickened state. The most common levels of liquid thickness used in dysphagia management are described along with challenges to naming these levels of thickness. A common standardized terminology and definitions for thickened liquids is recommended for improved patient safety.