Computational Fluid Dynamics Research On Human Upper Airway And Medical Application

Simulation of inner flow in human upper airway has an important value to research of many subjects, including fluid mechanics,olfaction,medicine. Findings in this field can be applied to explanation of olfaction mechanism and treatment of upper airway diseases. In recent years, computational fluid dynamics has been widely used in the research of this field. Although many productions have been gotten, plenty of questions are still waiting for further research.Obstructive sleep apnea hypopnea syndrome is a disease with an incidence about 2%～4% which has the characteristic of apnea and hypopnea during sleep. Generally, the disease has a close relationship with the abnormal structures in human upper airway and muscle activity change. The main treatments for the disease are oral appliance and continuous positive airway pressure (CPAP). The existing descriptions of disease and treatment mechanism are based on imaging study and it is too simple and not exact.In the presented work, based on the data from clinical treatment, exact human upper airway models were established. Using computational fluid dynamics, inner flow of human upper airway was simulated and the veracity of result was testified using experimental and clinical data. Furthmore, five flow models(Laminar,Standard k-ε, Low Re k-ε, Spalart-Allmaras, SST k-ω)were applied to simulate the inner flow of human upper airway. The results show that the simulation result of standard k-εhas an obvious error during the quiet breathing and Laminar model is recommended for simulation at this breathing state. Further research shows that oral cavity and position have moderate effect on human upper airway.Based on the above results, the inner flow of a patient's upper airway before and after above treatments were both simulated and the flow parameters were compared. After oral appliance treatment, the pharynx area of patient is remarkably enlarged. As a result, static pressure of pharynx is greatly enhanced. At the same time, velocity magnitude and resistance of pharynx are decreased. However, the flow parameters in nasal cavity show no obvious change at inspiration and expiration after treatment. The above change can be helpful to eliminate the collapse of pharynx and cure the disease.Continuous positive airway pressure treatment was simulated and response in flow field of upper airway were compared and analyzed under four different CPAP pressure levels. Flux changed linearly with the CPAP pressure. Along the flow direction, pressure, velocity and Re number increase with CPAP pressure. The result shows that CPAP is an effective treatment to prevent upper airway collapse. CPAP pressure will not do serious harm to patient's turbinate because of velocity limitation effect of nasal cavity.