Measurement and modelling of sensory-motor interactions between fluid rheology and swallowing biomechanics

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The act of swallowing is one that most people take for granted. Whether we are drinking a glass of water, or savouring a favourite main course, we swallow, unaware that the successful transport of food or fluid through our mouths and throats involves a complex interaction between oro-pharyngeal sensory function and the sequenced contraction of more than 38 paired muscles in the upper aerodigestive tract. The biomechanics of swallowing must be fine-tuned to deal with a variety of different food and liquid textures, and rely on sensory information for this fine-tuning. Thin liquids are arguably the most challenging texture to swallow safely, because they flow fast and can easily be aspirated (enter the airway) if swallowing biomechanics are mistimed. A long-term goal of the research in my laboratory is to better understand how swallowing biomechanics vary across liquids with different viscosities and to determine how sensory awareness of fluid flow characteristics (rheology) influences this variation. Breakdowns in this process are part of dysphagia (swallowing impairment), which has significant consequences both for health and for quality of life. Over the next 5 years, we have the following short-term goals: a) To measure the rheological (flow) characteristics of a variety of fluid stimuli, including those used in the assessment and management of swallowing impairment, such as barium contrast media and thickened liquids. b) To measure human sensory discrimination ability for small differences in fluid rheology, to identify the smallest perceivable differences. c) To measure a variety of physiological swallowing signals (tongue-palate pressures, electromyography, ultrasound, videofluoroscopy) to characterize human patterns of motor variation in response to differences in fluid flow. d) To develop and validate radiographic image analysis techniques (and associated user-friendly tools, such as Image-J plug-ins) to quantify physiological differences in swallowing biomechanics in response to differences in fluid rheology. e) To use these data arising from these previous goals to build a mathematical model that accurately accounts for the variation of swallowing biomechanics across perceivable differences in fluid viscosity. Integral to this program of research is the interprofessional training of highly qualified personnel from the disciplines of engineering and speech-language pathology (S-LP). We are requesting funding to support trainees from both disciplines in research and applied training opportunities. This will foster improved understanding of instrumentation and measurement for the S-LPs, and of the application of engineering and measurement techniques to a physiological context (swallowing impairment) for the engineers. Ultimately, this program of research will provide a foundation of rigorous measurement and empirical evidence upon which advancements in several different fields related to the management of swallowing disability can be built. These include the refinement and development of rheologically modified fluids for use in assessment and management contexts; the development of devices and protocols for objectively measuring swallowing motor behaviours; and the development of training techniques to support precise and accurate measurement of swallowing behaviours by healthcare professionals.