The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

MODELING OF RESPIRATORY ANATOMICAL EFFECTS ON EXPIRATORY AIRFLOW AND ACOUSTICS IN HUMAN NASAL AIRWAYS.

Jinxiang Xi1,2, JongWon Kim1, Xiuhua A. Si3, Haibo Dong4; 1Systems Engineering, University of Arkansas at Little Rock, Little Rock, AR; 2Mechanical and Biomedical Engineering, Central Michigan University, Mount Pleasant, MI; 3Engineering, Calvin College, Grand Rapids, MI; 4Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA

The intricate anatomy of the respiratory tract is believed to induce complex flow characteristics during exhalation before the air enters the nasal airways. However, this upstream effect on breathing resistance and sound production remains largely un-quantified within the upper respiratory airway. Specially, we hypothesize that the airway constriction due to the hanging uvula is one major cause that initiates flow instabilities and sleep disorders. The objective of this study is to systematically assess the effect of the larynopharyneal anatomical details on the expiratory airflow and acoustic characteristics in human nasal airways by means of numerical methods. To achieve this objective, a physiologically realistic extrathoracic airway was developed that extends from the nasal nostrils to the upper trachea based on human medical images. Both Reynolds Stress Model (RSM) and Large Eddy Simulations (LES) were employed to simulate the laminar, transitional and fully turbulent flow regimes for a spectrum of flow rates covering 4 - 45 L/min. We found large effect from the laryno-pharyngeal geometries on the exhaled airflows that enter the nasal cavity. In particular, the variation of the uvula position may significantly alter the breathing resistance. Abrupt pressure drops has been observed to result from the uvula-related airway obstruction when the human subject takes a supine position. Results of this study indicate that the uvula position is a major cause for sleep disorders such as snoring or obstructive sleep apnea syndrome. Sponsored Research - None Effect of uvula-obstruction on snore generation using Reynolds Stress Model (anisotropic turbulence) and Broadband Noise Model (acoustics). SAPL: surface acoustic power level.