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Objective To establish the feasibility of a noninvasive method to identify pharyngeal airflow characteristics in sleep-disordered breathing. Methods Four patients with sleep-disordered breathing who underwent surgery or used positive airway pressure devices and four normal healthy controls were studied. Three-dimensional CT imaging and computational fluid dynamics modeling with standard steady-state numerical formulation were used to characterize pharyngeal airflow behavior in normals and pre-and post-treatment in patients. Dynamic flow simulations using an unsteady approach were performed in one patient. Results The pre-treatment pharyngeal airway below the minimum cross-sectional area obstruction site showed airflow separation. This generated recirculation airflow regions and enhanced turbulence zones where vortices developed. This interaction induced large fluctuations in airflow variables and increased aerodynamic forces acting on the pharyngeal wall. At post-treatment, for the same volumetric flow rate, airflow field instabilities vanished and airflow characteristics improved. Mean maximum airflow velocity during inspiration reduced from 18.3±5.7 meters/second pre-treatment to 6.3±4.5 meters/second post-treatment (p=0.002), leading to a reduction in maximum wall shear stress from 4.8±1.7 Pascals pre-treatment to 0.9±1.0 Pascals post-treatment (p=0.01). The airway resistance improved from 4.3±1.4 Pascals/Liter/minute at pre-treatment to 0.7±0.7 Pascals/Liter/minute at post-treatment (p=0.004). Post-treatment airflow characteristics were not different from normal controls (all p≥0.39). Conclusion This study demonstrates that pharyngeal airflow variables may be derived from CT imaging and computational fluid dynamics modeling, resulting in high quality visualizations of airflow characteristics of axial velocity, static pressure and wall shear stress, in sleep-disordered breathing.

A dynamic 3D CT technique of the upper airway is described that can be performed with a clinically reasonable radiation dose and sets a benchmark for future use.