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


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.


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

Subject Categories

Communication Sciences and Disorders


© Miranda J. White