Pulmonary Airway Reopening: Effects of Non-Newtonian Fluid Viscosity

[+] Author and Article Information
H. T. Low, Y. T. Chew, C. W. Zhou

Department of Mechanical & Production Engineering, The National University of Singapore, 10 Kent Ridge Crescent, Singapore 119250

J Biomech Eng 119(3), 298-308 (Aug 01, 1997) (11 pages) doi:10.1115/1.2796094 History: Received November 07, 1994; Revised September 06, 1996; Online October 30, 2007


This paper considers the effects of non-Newtonian lining-fluid viscosity, particularly shear thinning and yield stress, on the reopening of the airways. The airway was simulated by a very thin, circular polyethylene tube, which collapsed into a ribbonlike configuration. The non-Newtonian fluid viscosity was described by the powerlaw and Herschel-Buckley models. The speed of airway opening was determined under various opening pressures. These results were collapsed into dimensionless pressure-velocity relationships, based on an assumed shear rate γ̇ = U/(0.5 H), where U and H are the opening velocity and fluid film thickness, respectively. It was found that yield stress, like surface tension, increases the yield pressure and opening time. However, shear thinning reduces the opening time. An increased film thickness of the non-Newtonian lining fluid generally impedes airway reopening; a higher pressure is needed to initiate the airway reopening and a longer time is required to complete the opening process.

Copyright © 1997 by The American Society of Mechanical Engineers
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