A computational study of the respiratory airflow characteristics in normal and obstructed human airways.
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Date
2014-08-18
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Abstract
Obstructive lung diseases in the lower airways are a leading health concern worldwide To improve our understanding of the pathophysiology of lower airways we studied airflow characteristics in the lung between the 8th and the 14th generations using a three dimensional computational fluid dynamics model where we compared normal and obstructed airways for a range of breathing conditions We employed a novel technique based on computing the Pearson s correlation coefficient to quantitatively characterize the differences in airflow patterns between the normal and obstructed airways We found that the airflow patterns demonstrated clear differences between normal and diseased conditions for high expiratory flow rates 2300ml s but not for inspiratory flow rates Moreover airflow patterns subjected to filtering demonstrated higher sensitivity than airway resistance for differentiating normal and diseased conditions Further we showed that wall shear stresses were not only dependent on breathing rates but also on the distribution of the obstructed sites in the lung for the same degree of obstruction and breathing rate we observed as much as two fold differences in shear stresses In contrast to previous studies that suggest increased wall shear stress due to obstructions as a possible damage mechanism for small airways our model demonstrated that for flow rates corresponding to heavy activities the wall shear stress in both normal and obstructed airways was Under0 3Pa which is within the physiological limit needed to promote respiratory defense mechanisms In summary our model enables the study of airflow characteristics that may be impractical to assess experimentally