Thesis Title

A Systematic Investigation of the Linearity of Liquid Flow Under Line-Spread Testing

Date of Graduation

Spring 2007


Master of Science in Communication Sciences and Disorders


Communication Sciences and Disorders

Committee Chair

Lynette Goldberg


dysphagia, viscosity, Line-Spread Test, thickening agents, Newtonian liquid, non-Newtonian liquid

Subject Categories

Communication Sciences and Disorders


Thickened liquids frequently are used to facilitate a safe swallow in persons with dysphagia. The lack of a clinically objective way to ensure consistency in these thickened liquids is of concern. The Line-Spread Test (LST) has promise; however, its validity and reliability need to be further studied. The current study sought to compare the nature and rate of flow of nectar-thick Newtonian (naturally occuring apricot nectar) and non-Newtonian (bottled water thickened with two starch-based agents, Thick it and Thick & Easy) liquids under line-spread testing. Three trials of each liquid were filmed. Liquid flow was examined frame-by-frame (30 frames per second) using a VHS/DV converter on a television monitor. Pearson r correlation coefficients were run to determine the relationship of liquid flow collapsed across the LST quadrants and with quadrants considered individually. Results showed a statistically significant strong, negative relationship between Newtonian and non-Newtonian liquids. Non-Newtonian liquid continued to flow across time. In contrast, Newtonian liquid approached maximal distance flow 1 second following its release, with limited flow over the remaining 59 seconds. There was a significant negative relationship between the two starch-based thickening agents, although the distance flowed was close. With liquid flow considered between quadrants, apricot nectar had a similar flow pattern to Thick It. Interestingly, the non-Newtonian liquid evidenced a more linear spreading pattern than the Newtonian liquid. Recommendations are made for LST measurement to realize its promise as an alternative method of assessing the flow of thickened liquids.


© Miranda J. White