The practice of thickening liquids has become one of the most frequently used interventions for swallowing impairment (dysphagia). However, the terminology used to describe thickened liquids (such as nectar-thick and honey-thick) is subjective and we lack empirical evidence about how alterations in liquid consistency affect swallowing function and physiology. The International Dysphagia Diet Standardisation Initiative is a multidisciplinary task force ( that has recently developed a new taxonomy of terms to label different levels of liquid consistency used in dysphagia management; these are paired with operational definitions and practical gravity-flow measurement techniques that can be used by caregivers and clinicians to confirm the category of any liquid at the time of preparation or serving. The goal of the current proposal is to measure the in vitro physiological flow of liquids representative of the IDDSI levels of liquid consistency (thin, slightly-thick, milly-thick, moderately-thick and extremely-thick). Physiological measures of liquid flow require an understanding both of the rheological properties of the liquid (gravity-flow; viscosity) and the forces that are applied to the liquid during swallowing (tongue pressure; swallowing muscle contraction). Additional sensory attributes of the bolus (such as slipperiness, graininess and cohesiveness) are also likely to be relevant. We will measure these properties and study bolus flow in healthy adults to establish a reference perspective of expected flow in the context of healthy tongue pressure generation. We will then collect comparative measures in individuals with dysphagia of different etiologies (stroke, acquired brain injury, oropharyngeal cancer, post cervical spine surgery, and neurodegenerative disease) to determine how alterations in swallowing motor function impact liquid flow. These measurements will provide information to guide clinicians in determining optimal levels of thickening to recommend for patients with dysphagia. This research is highly significant because it will establish a new foundation of understanding with respect to the influence of thickened liquids on swallowing. This is essential for advancing clinical practice and setting the stage for future treatment efficacy research.

Public Health Relevance

Thickened liquids have become the most common intervention for dysphagia (swallowing impairment), yet we lack a clear understanding of how this intervention works to achieve clinical benefit. In this project, we will advance our understanding of how thickening influences swallowing by measuring the physiological flow of 5 incremental degrees of liquid thickening. These measures of physiological flow will take into consideration both the physical flow properties of these liquids and the forces applied during swallowing by healthy adults and individuals with swallowing impairment due to stroke, brain injury, oropharyngeal cancer, post cervical spine surgery and neurodegenerative disease.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Study Section
Motor Function, Speech and Rehabilitation Study Section (MFSR)
Program Officer
Shekim, Lana O
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University Health Network
Zip Code
M5 2C4
Ong, Jane Jun-Xin; Steele, Catriona M; Duizer, Lisa M (2018) Sensory characteristics of liquids thickened with commercial thickeners to levels specified in the International Dysphagia Diet Standardization Initiative (IDDSI) framework. Food Hydrocoll 79:208-217
Steele, Catriona M (2018) The influence of tongue strength on oral viscosity discrimination acuity. J Texture Stud 49:249-255
Namasivayam-MacDonald, Ashwini M; Barbon, Carly E A; Steele, Catriona M (2018) A review of swallow timing in the elderly. Physiol Behav 184:12-26
Barbon, Carly E A; Steele, Catriona M (2018) Characterizing the Flow of Thickened Barium and Non-barium Liquid Recipes Using the IDDSI Flow Test. Dysphagia :
Waito, Ashley A; Tabor-Gray, Lauren C; Steele, Catriona M et al. (2018) Reduced pharyngeal constriction is associated with impaired swallowing efficiency in Amyotrophic Lateral Sclerosis (ALS). Neurogastroenterol Motil 30:e13450
Steele, Catriona M; Namasivayam-MacDonald, Ashwini M; Guida, Brittany T et al. (2018) Creation and Initial Validation of the International Dysphagia Diet Standardisation Initiative Functional Diet Scale. Arch Phys Med Rehabil 99:934-944
Waito, Ashley A; Valenzano, Teresa J; Peladeau-Pigeon, Melanie et al. (2017) Trends in Research Literature Describing Dysphagia in Motor Neuron Diseases (MND): A Scoping Review. Dysphagia 32:734-747
Peladeau-Pigeon, Melanie; Steele, Catriona M (2017) Age-Related Variability in Tongue Pressure Patterns for Maximum Isometric and Saliva Swallowing Tasks. J Speech Lang Hear Res 60:3177-3184
Cichero, Julie A Y; Lam, Peter; Steele, Catriona M et al. (2017) Development of International Terminology and Definitions for Texture-Modified Foods and Thickened Fluids Used in Dysphagia Management: The IDDSI Framework. Dysphagia 32:293-314
Namasivayam-MacDonald, Ashwini M; Burnett, Lynsey; Nagy, Ahmed et al. (2017) Effects of Tongue Strength Training on Mealtime Function in Long-Term Care. Am J Speech Lang Pathol 26:1213-1224

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