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Title: Rheological characterisation of commercially available thickeners for patients with dysphagia
Author: Payne, Clare
ISNI:       0000 0004 2741 1117
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2012
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People with dysphagia may be given thickened fluids to promote a safer swallow where there is a risk of aspiration with thin or normal fluids. These are thickened using polysaccharide products, which may be starch-based, gum-based or combination systems. In the UK at present, these are mainly starch based, although some gum -based products are beginning to appear on the commercial market. There are many problems with the preparation ofthese drinks, meaning patients do not always receive the consistency they have been assessed to receive. These issues include the interaction of the polysaccharides, especially starch, with other ingredients, the build up of drink thickness over time and changes in drink thickness associated with temperature. Although the incidence of dysphagia is unknown and it is unclear how many people are affected by this, the numbers are increasing with our increasingly aged population and the consequences of poorly managed dysphagia are many. These range from dehydration to aspiration pneumonia, which, in severe cases can lead to death. During this study, the commercial products were characterised to be non-Newtonian viscoelastic, shear-shinning fluids with history dependence and a yield point, which increases with concentration. Clinically, the fluids are classified into three classes based on thickness, the names of which vary both nationally and internationally. However by any of the classification systems, this study found that drinks supposed to be ofthe same class _ were not, even for the same thickener type prepared by the same person. Reasons included drink type, temperature, lack of training or inadequate instruction; and the inconsistencies were seen for both viscosity and viscoelastic properties. The relationship between perceived and instrumental viscosity was different from that found in Newtonian fluids, denoting that viscoelasticity plays a part in oral perception. This relationship was found to be different in hot and cold drinks; and different according to how the physical viscosity was altered. Starch-based thickeners were less stable in terms of ingredient interaction and more temperature dependent; xanthan gum performed particularly well in both areas. The variation between products was investigated, and thought to be due to differences in the solution structure of the different polysaccharides; xanthan gum having a very ordered structure and lower molecular weight. From the results of this study is it recommended that more information, training, instruction and assessment be provided for thickening drinks of different types; and the use of pre-thickened fluids or products with pre-weighed thickener and ingredients should be increased. Future work to improve the situation could look at optimal viscoelastic structure for swallowing, realistic oral shear rates and the use of gums such as xanthan in future products. ii
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available