Effects of partial middle turbinectomy with varying resection volume and location on nasal functions and airflow characteristics by CFD
Introduction
Respiratory physiology and pathology are strongly dependent on the airflow inside the nasal cavity. Since nasal airflow is heavily affected by the geometry of the flow passage, changes in the anatomical shape of the nasal cavity, due to diseases or surgical treatments, alter the nasal resistance and functions of nose.
One of the surgical modifications is the partial middle turbinectomy (MT). Usually the partial resection is done during endoscopic sinus surgeries (ESS) for the patients with chronic sinusitis with polyps and endoscopic endonasal skull base surgeries. There still exist controversies regarding the resection or preservation of the middle turbinate during functional endoscopic sinus surgery [14,28]. Although it is generally accepted by rhinologists that a diseased or flail middle turbinate should be excised, air-conditioning, filtration functions, possible loss of olfaction, and empty nose syndrome (ENS) after MT are of concern [14]. Radical resection of middle turbinate seems to be associated with an increased incidence of complication. The effect of partial MT was investigated experimentally by using the particle image velocimetry(PIV) technique with unilateral nasal cavity models [4], [19]. The change in velocity field according to the extent of resection volume was investigated and the change of main flow direction and root mean square velocity was observed. The effect of the presence of inferior and middle turbinate was investigated by PIV and CFD techniques with simplified models [17]. They concluded that the presence of inferior turbinate was more important than the middle turbinate on the flow during inspiration.
In the last decade, CFD has become a fast and convenient research tool to study airflow in the human airway [1], [6], [7], [20], [23], [24], [27], [29], especially when investigating heat and humidity transfer, which is not easy to study by using other experimental techniques. There had been numerical studies on partial inferior turbinectomy [2], [15], [24].
Zuber et al. [29] studied the impact of middle turbinate in flow behavior and air conditioning ability of the nose by CFD. They concluded that turbinates play a vital role in conditioning of the inspired air and therefore alteration of turbinate structure would seriously hamper its air-conditioning ability. Di et al. [5] investigated nasal airflows in two virtual bilateral turbinectomy models (total resection of middle and inferior turbinate) by CFD, in connection with the pathogenesis of ENS. They correlated nasal aerodynamic changes with two different symptoms of ENS and proposed a new hypothesis that the increased velocities around the sphenopalatine ganglion (medial and lateral portion of the posterior part of the nasal cavity before nasopharynx or medial and lateral part before posterior choana) in the ENS-MT model is responsible for headache in ENS-MT patients. Zhao et al. [28] studied airflow in pre- and post-MT(partial) models of a specific patient by CFD to find the effect of the presence of middle turbinate. Streamlines, air flux distribution, and wall shear stress distribution for middle turbinectomy model were generally similar to those of the normal structures and the nasal resistances decreased by 20% after radical middle turbinectomy. Dayal et al. [8] studied the effects of total middle (TMT) and inferior (TIT) turbinectomy on nasal aerodynamics by comparing CFD results for pre- and virtual surgery models of 10 patients with hypertrophy. They investigated changes in nasal resistance and air-conditioning efficiency post-operatively, and concluded that TIT yields greater increases in nasal airflow but also impairs the nasal air-conditioning capacity to a greater extent than TMT. Yet, the effect of partial turbinectomy, especially according to the extent of removal, has not been evaluated up to now.
Recent studies indicate that nasal secretion from the mucosa/mucous membrane of the nasal cavity is not only important for air conditioning, brain cooling, and defense, but also for olfactory function [16]. Even-Tzur et al. [11] conjectured that wall shear stress (WSS) on epithelial cells caused by airflow activates nasal secretion by in-vitro experiments in cultured human nasal epithelial cells, and this was cited by Hildebrandt et al. [16]. Therefore the wall shear stress distribution in the olfactory region might be related with nasal secretion and nasal functions, such as air-conditioning, filtration and olfaction.
In this article, airflows inside a normal (pre-surgery) model and six kinds of virtual partial MT (post-surgery) models including near total MT were investigated by CFD. Using comparative study of CFD results for pre- and post-MT models, we extracted the tendency of post-surgical changes in nasal functions and resistance with respect to turbinate resection volume, location, and surgical technique. Furthermore, we closely examined flow-rate and WSS distributions in connection with nasal secretion. Since secretion substances act as a solvent for odors and enable their adhesion to the surface of olfactory cells [16], WSS may affect the olfactory function of nose. Therefore, we hypothesized that WSS on epithelial cells in the olfactory region is likely correlated with mucus secretion and possibly olfaction function of nose. The spatial and temporal changes of WSS distribution in the olfactory region were examined to investigate the influence of a series of virtual MT on the nasal secretion and functions.
Although the surgical simulation was done for a single case, we postulate that removal of the anterior inferior part of middle turbinate while preserving posterior margin will not disturb the airflow characteristics and physiological functions of nose excessively.
Section snippets
Material and methods
Creation of a correct flow passage is essential to analyze the flow inside a complex flow passage such as nasal cavity by CFD. The anatomically accurate unilateral nasal cavity model [4], [24] was chosen retrospectively as a normal model (pre-surgery model). Institutional Review Board of the Samsung Medical Center approved this study. Virtual surgery models were created by alteration of the normal model by cooperation between engineers and ENT doctors. Virtual turbinectomy was done manually in
Results
The steady inspiratory flows with a constant flow rate of 250 mL/s and rest respirational flows in one normal and six virtual surgery models were solved by use of the aforementioned numerical scheme. CFD results of nasal resistance (pressure drop), total wall heat transfer, flow-rate partitioning, and outlet temperature are summarized in Table 1.
Discussion
The benefits and drawbacks of partial MT were considered by looking at the changes in global (pressure drop, flow partitioning, and total wall heat transfer) and local (velocity, temperature, humidity, pressure gradient, wall shear stress, and exit temperature) properties of CFD results. Global and local changes in M1 and M2 model were not significant, which support the postoperative clinical and endoscopic findings that revealed no difference in the incidence of frontal sinusitis or frontal
Conclusion
The effect of partial MT on the nasal functions and resistance, according to the extent and location of removal, was investigated by numerical simulations of nasal airflow in the variations of simulated MT models. Using the computational fluid dynamics (CFD) results of pre- and virtual surgery models, the level of changes in physiological factors with respect to resection volume and location was identified. While the physiological and pathological changes in four partial MT model were
Acknowledgment
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (2011-0028942).
Kyun Bum Lee graduated from the Konkuk University College of Engineering in 2014 and also received his BSE in Mechanical Engineering in 2014 from Konkuk University, Seoul, Korea. He studied in the graduate school of Konkuk University since 2014. In fluid dynamics competition of KSME(December 2013), he received a bronze prize. His research interests are Flow Visualization, PIV, Biofluid Engineering and CFD.
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2021, Respiratory Physiology and NeurobiologyCitation Excerpt :There have been extensive computational studies investigating different nasal surgeries and their effect on nasal airflow (Xiong et al., 2008; Rhee et al., 2011; De Wang et al., 2012; Frank et al., 2013a; Hariri et al., 2015; Dayal et al., 2016; Maza et al., 2019; Inthavong et al., 2019; Siu et al., 2020a), which showed the ability of virtual surgery to guide surgical interventions to alleviate nasal airway obstruction. Previous CFD studies of middle turbinate resection (Zhao et al., 2014; Alam et al., 2019; Lee et al., 2016) have demonstrated shifts in airflow toward the area of middle turbinate resection and decreased airflow velocity, decreased wall shear stress, and increased local air pressure. A recent outcome from DelGaudio et al. (2019)'s analysis of patients with middle turbinate resection suggested that the surgery removed the middle turbinate protective function in preventing inhaled allergen particles from depositing on the septum.
Kyun Bum Lee graduated from the Konkuk University College of Engineering in 2014 and also received his BSE in Mechanical Engineering in 2014 from Konkuk University, Seoul, Korea. He studied in the graduate school of Konkuk University since 2014. In fluid dynamics competition of KSME(December 2013), he received a bronze prize. His research interests are Flow Visualization, PIV, Biofluid Engineering and CFD.
Young Sun Jeon graduated from the Konkuk University College of Engineering in 2015 and also received his BSE in Mechanical Engineering in 2015 from Konkuk University, Seoul, Korea. He studied in the graduate school of Konkuk University since 2015. His research interests are Flow Visualization, PIV, Biofluid Engineering and CFD.
Seung-Kyu Chung graduated from the Yonsei University College of Medicine in 1980. He finished his Otolaryngology residency training at Yonsei University Medical Center, Seoul, Korea and got Korean board of Otolaryngology in 1984. He received his Ph.D. at Yonsei University Postgraduate School in 1989. He is working as rhinologist at the Department of Otorhinolaryngology, Head and Neck Surgery, Samsung Medical Center, Seoul, Korea since 1994. His research interests are anatomy, 3D reconstruction and air flow of the nasal cavity.
Sung Kyun Kim received his MSE in Naval Architecture in 1982 from Seoul National University. He also received his Ph.D. in Naval Architecture and Marine Engineering in 1988 from University of Michigan, Ann Arbor. He worked in department of mechanical engineering, University of California, Berkeley as a visiting professor in 1997. He works in the Department of Mechanical engineering, Konkuk University, Seoul, Korea as a professor since 1988. His research interests are Flow Visualization, PIV, Biofluid Engineering, Flow Induced Vibration and Streaming Flow.