The viscosity of non-solid foods, and the stability of their viscosity with changes in time, temperature and shearing is critical in managing chronic swallowing difficulties known as dysphagia. The starch-based foodstuffs thickeners used in dysphagia therapy are highly non-Newtonian and their viscosity dependent on these variables. This research addresses the starch fluids' rheological complexity. It also establishes the quartz crystal microbalance (QCM) as an objective device capable of measuring viscosity of complex non-Newtonian fluids at the patient bedside.

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

Taking medicines is a frequent problem for patients with dysphagia (PWD). This study aimed to: identify the nature of the problems encountered by patients and healthcare professionals; quantify the problems in an acute care setting; trial individual medicine administration guides (I-MAGs) in order to help nurses correctly administer medicines to PWD. Methods A qualitative methodology was used comprising of interviews with PWD to gain an in-depth insight into taking medicines and a focus group of healthcare professionals to explore the problems of medicine administration. Direct observation of medicine administration rounds was utilized to identify if the medicine administration error (MAE) rate and severity was greater for PWD than those without in four acute hospitals in the UK. In one of the hospitals a controlled trial of I-MAGs was employed together with direct observational medicine rounds and nurse questionnaires to identify if the MAE rate for PWD could be decreased and if the I-MAGs led to an increase in nurses' knowledge. Results The qualitative research identified eight themes the central two being the importance of medicine formulation for PWD and the identification that medicine management falls into the province of five different professional groups putting the PWD at risk of fragmented care. The MAE rate was significantly higher for PWD than for patients without, and was even higher for those with enteral tubes. There was however no difference in error severity. Introduction of I-MAGs did not result in a decrease in MAEs on the intervention wards or an increase in nurses' knowledge. Unexpectedly the MAE rate fell significantly on the control wards. Conclusions Medicine management for PWD crosses discipline boundaries and requires those professionals to work together to reduce MAEs and ensure patients receive their medicines in a formulation which they can take safely.

Swallowing is a complex neurophysiological process involving the activation of several components of the central nervous system with bilateral but asymmetric representations of swallowing musculature in the motor cortex. Difficulty in swallowing (dysphagia) in stroke patients has been reported by up to 50% of victims, and can increase morbidity and mortality in this population due to the development of aspiration pneumonia and malnutrition. One of the common factors that predispose patients to dysphagia after a stroke is believed to be the reduced sensory awareness in the oropharyngeal area, which affects the swallowing process. The uses of diet modification to reduce thin liquid aspiration have gained interest but are often unpalatable or have limited success. Carbonated liquid have shown some beneficial effects in swallowing behaviour. However, there is very little evidence to support this intervention. Therefore, the aim of this thesis is to investigate the neurophysiological and behavioural effects of carbonated liquids on swallowing in healthy volunteers.The effects of carbonated solutions on swallowing performance compared to non-carbonated solutions (still water) was investigated in a pilot study and (still water and citric acid) in the main study using reaction time task (chapter 2). Carbonation appears to alter swallowing performance compared to other liquids by improving complex tasks. In addition, beneficial neurophysiological effects of carbonated liquids were evident after 10 minutes of carbonated liquid swallowing compared to still water and citric acid solution in healthy volunteers (chapter 3).In chapter 4, the response of the healthy swallowing motor cortex to carbonated liquids following application of a virtual lesion compared to still water and saliva swallowing, was investigated. Carbonated liquids were able to reverse the inhibitory effect induced by 1 Hz rTMS to the dominant pharyngeal motor representation. Moreover, the beneficial effects of carbonated liquids on swallowing performance, measured with a swallowing reaction times task after application of a virtual lesion was observed in a pilot investigation in healthy volunteers (chapter 5). These data demonstrate that carbonated liquids have beneficial neurophysiological and swallowing performance effects and support notion that the chemical properties of carbonated liquids may provide the required peripheral sensory information that alter the brain swallowing function, which leads to an improvement in the swallowing performance of stroke dysphagic patients. These data lay the foundation for considering the use of carbonation as facilitating stimuli in dysphagic patients.