Computational fluid dynamics analysis of upper airway reconstructed from magnetic resonance imaging data.
OBJECTIVE
We performed flow computations on an accurate upper airway model in a patient with obstructive sleep apnea and computed the velocity, static pressure, and wall shear stress distribution in the model.


METHODS
Cartesian coordinates for airway boundaries were determined from cross-sectional magnetic resonance images, and a 3-dimensional computational model of the upper airway was constructed. Flow simulations were then performed within a FLUENT commercial software framework. Four different flow conditions were simulated during inspiration, assuming the steady-state condition. The results were analyzed from the perspectives of velocity, static pressure, and wall shear stress distribution.


RESULTS
We observed that the highest axial velocity was at the site of minimum cross-sectional area (retropalatal pharynx) resulting in the lowest level of wall static pressure. The highest wall shear stresses were at the same location. The pressure drop was significantly larger for higher flow rates than for lower flow rates.


CONCLUSIONS
Our results indicate that the presence of airway narrowing, through change in the flow characteristics that result in increased flow velocity and reduced static pressure, can itself increase airway collapsibility. Additionally, the effects of wall shear stress on airway walls may be an important factor in the progression over time of the severity of obstructive sleep apnea.
Mihaescu
Mihai
M
Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Ohio, USA.
Murugappan
Shanmugam
S
Gutmark
Ephraim
E
Donnelly
Lane F
LF
Khosla
Siddarth
S
Kalra
Maninder
M
D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D011312:Pressure; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology