Effects of Functional Endoscopic Sinus Surgery on Nasal Air Flow - A Computational Fluid Dynamics Study

Functional endoscopic surgery (FESS) is usually carried out for noses with chronic nasal obstructions. The aim of this study was to evaluate the effects of FESS on nasal airway aerodynamic changes compared with a healthy nose using computational fluid dynamics (CFD) simulations. Numerical flow simulations were performed for the nasal cavity model with the FESS procedure. The Reynolds averaged Navier-Stokes equations were numerically solved for laminr-turbulent-transition flow inside using FLUENTs 6.3. Comparisons of the internal aerodynamic flow patterns between the FESS case and a previous published healthy nose case, and possible surgical consequences were investigated and discussed. For the healthy nose, most of the airflow was symmetrical around the inferior turbinate along the middle septum and a very small portion went into the sinus regions. However, for the post-FESS case, there was relatively more airflow on the left cavity, which went into the left maxillary, ethmoid and sphenoid sinus regions; the number and distribution of local circulations in the ethmoid and sphenoid sinus regions changed for inspirational and expiratory airflow. With an inspiration flow rate of 20.4 L/min, local maximum velocity and wall shear stress around the FESS region were 1.08 m/s and 0.126 pascal with a nasal resistance of 0.085 pa s/cm

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from the nostril to nasopharynx. With a larger inspirational flow rate, the local pressure into the left maxillary sinus decreased faster than that into the right one around the FESS region. Current results demonstrate the airflow pattern changes of a nasal cavity between the healthy and post-FESS cases which may affect normal nasal function. Considering possible consequences on local NO transfer related to human immunologic reactions and cilium motion around the ostia, such kind of conventional FESS procedure should be carefully planned before surgery.