Fluid-structure interaction modeling of upper airways before and after nasal surgery for obstructive sleep apnea.

Nasal obstruction frequently has been associated with obstructive sleep apnea (OSA). Although correction of an obstructed nasal airway is considered an important component in OSA treatment, the effect of nasal surgery on OSA remains controversial. Variation in airway anatomy between before and after nasal surgery may cause significant differences in airflow patterns within the upper airway. In this paper, anatomically accurate models of the interaction between upper airway and soft palate were developed from prenasal and post-nasal surgery multidetector computed tomography data of a patient with OSA and nasal obstruction. Computational modeling for inspiration and expiration was performed by using fluid-structure interaction method. The airflow characteristics such as velocity, turbulence intensity and pressure drop, and displacement distribution of soft palate are selected for comparison. Airway resistances significantly decrease after the nasal surgery, especially in the velopharynx region because of an enlarged pharyngeal cavity and a reduced upstream resistance. Meanwhile, the decreased aerodynamic force would result in a smaller displacement of soft palates, which would lead to slight impact of the soft palate motion on the airflow characteristics. The present results suggest that airflow distribution in the whole upper airway and soft palate motions have improved following nasal surgery.