The Importance of Extensional Rheology in Bolus Control during Swallowing

Enrico Karsten Hadde,Julie Ann Yvette Cichero,Wei Chen,Jianshe Chen,Shaofeng Zhao

doi:10.1038/s41598-019-52269-4

Enrico Karsten Hadde, Julie Ann Yvette Cichero + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-52269-4

Copy DOI

Abstract

Thickened fluids are commonly used in the medical management of individuals who suffer swallowing difficulty (known as dysphagia). Previous studies have shown that the rheological properties of a liquid affect the flow behavior of the bolus in swallowing, such as pharyngeal transit time. While there is no doubt that shear rheology is a highly important factor for bolus flow, it is suspected that extensional properties of a liquid bolus also plays an important role in swallowing, due to elongation of the bolus as it flows through the oropharynx. Our aim in this work was to observe the effect of extensional viscosity on pharyngeal transit time and elongation of the bolus during swallowing. Eight samples of thickened liquid barium that were shear-controlled, but varied in extensional viscosity and two samples that were extensional-controlled, but varied in shear viscosity were swallowed by eight healthy individuals. Data were collected under lateral view of videofluoroscopy swallow study (VFSS); measures of pharyngeal transit time and the ratio of the length to the width of the bolus on the frame of Upper Esophageal Sphincter (UES) opening were taken from the VFSS recordings. It was observed that the pharyngeal transit time generally increases when the fluids are thickened to higher IDDSI consistency. Additionally, higher extensional viscosity fluids reduced the elongation of the bolus during swallowing, thus potentially reducing the risk of post-swallow residue due to bolus breakage. This study confirmed the relevance of the extensional viscosity of the bolus in swallowing.

Highlights

Difficulty of swallowing food or fluid, known as dysphagia is a major issue throughout the world[1,2]
Fluids that were thickened with xanthan gum thickener have much higher maximum extensional viscosity than fluids that were thickened with modified starch thickener at similar shear viscosity at 50 s−1
The pharyngeal transit time generally increases when the fluids are thickened to higher International Dysphagia Diet Standardisation Initiative (IDDSI) drink thickness levels

Summary

Introduction

Difficulty of swallowing food or fluid, known as dysphagia is a major issue throughout the world[1,2]. In 2013, International Dysphagia Diet Standardisation Initiative (IDDSI), a group of volunteers from diverse professions was established to develop a global standardized terminology and definitions for texture-modified foods and thickened fluids for individuals with dysphagia[13]. It was reported that higher shear viscosity slowed down the flow of the bolus in the pharynx, leading to longer pharyngeal transit time. Previous studies showed that for similar shear viscosity at 50 s−1, the extensional viscosity of the fluids was highly dependent on the type of thickeners[21,22,23]. Fluids that were thickened with xanthan gum thickener have much higher maximum extensional viscosity than fluids that were thickened with modified starch thickener at similar shear viscosity at 50 s−1. It is noted that the effects of bolus properties to swallowing behaviour will differ between dysphagia patients and healthy individuals

Objectives

Methods

Results

Discussion

Conclusion