The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

NASAL-PHARYNGEAL TISSUE COMPLIANCE AND AIRFLOW PATTEN DURING TIDAL BREATHING USING REAL-TIME MRI AND COMPUTATIONAL FLUID DYNAMICS.

Jinxiang Xi1,2, Xiawei Ou3; 1Department of Systems Engineering, University of Arkansas at Little Rock, Little Rock, AR; 2Department of Mechanical and Biomedical Engineering, Central Michigan University, Mount Pleasant, MI; 3Department of Radiology, University of Arkansas for Medical Science, Little Rock, AR

The respiratory airway varies both in morphology and dimension during a respiratory cycle due to tissue compliance, which in turn induces variations in airflow pattern and inhaled aerosol dynamics within. In this study, the tissue compliance in the nasal-pharyngeal airway was quantified using dynamic MR imaging during tidal breathing under both quite (before excise) and active (after exercise) physical conditions. The dynamically deforming 3-D airway morphologies were rendered with 10 increments during inhalation and another 10 increments during exhalation, which were then discretized for computational analysis. Both Lower-Reynolds k-? Turbulence model and large eddy simulations (LES) were employed to simulate the laminar, transitional and fully turbulent flow regimes under both quite and active tidal breathing activities. We found that the maximum intranasal tissue compliance is within the range 3-9%, and does exhibit noticeable discrepancy between quite and active breathing conditions. The pharyngeal tissue was much more compliant subject to physical activities, i.e., maximum tissue compliance being 5% under quite breathing and 9% under active breathing. The resultant airway change due to tissue compliance significantly alters the inhaled and exhaled airflow patterns in comparison to those within rigid airway geometries. Specifically, the normal stress upon the airway surface and the breathing resistance were calculated and compared between the cases with and without tissue compliance. Results of this study indicate that the pharyngeal tissue compliance is a major cause for obstructive sleep apnea or respiratory distress syndromes. Sponsored Research - None Upper airway morphology change during quite breathing obtained using real-time MRI.