Numerical simulation of airflow patterns in nose models with differently localized septal perforations

Introduction Numerous surgical techniques exist to treat nasal septal perforation (NSP). The surgical closure of large NSPs (>2cm) is still challenging. Posterior septectomy has been reported as a simple alternative to treat large NSP, yet its mechanisms for symptom relief are not clear, and if failed, its consequence cannot be easily reversed. Methods Ten NSP patients were recruited: five underwent posterior septectomy and five conventional flap or button repair. Computational Fluid dynamics (CFD) simulated the nasal aerodynamics based on CT scans. All patients had preoperative CT, however, only four had postoperative CT – two underwent posterior septectomy and the other two flap repair. We examined surgical outcomes and the nasal airflow features among the two treatment options. Results Both groups of patients had good outcomes based on chart review. Patients undergoing septectomy had significantly larger perforation size (2.32±0.87 vs 1.21±0.60 cm), higher flow rate across the perforation (47.8±28.6 vs. 18.3±12.2 ml/s) and higher wall shear stress (WSS) along the posterior perforation margin (1.39±0.52 vs. 1.15±0.58 Pa). The posterior WSS significantly correlate with cross-over flow velocity (r=0.77, p=0.009) and was reduced by almost 67% post-septectomy, and by 29% post-repair. Conclusions This is the first CFD analysis on NSP patient cohort. NSP resulted in flow disturbance and increased WSS that potentially lead to symptomatology. The removal of high stress points along the posterior margin may explain why posterior septectomy can be an effective treatment option. Aerodynamic abnormalities, in addition to perforation size and location, could serve as basis for future treatment decisions.

Section: Resultssupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Computational fluid dynamics evaluation of posterior septectomy as a viable treatment option for large septal perforations

Otto

Farag

et al. 2017

“…Most earlier CFD studies were limited in clinical value as they were all based on virtual perforations of healthy controls or non‐NSP patients. For example, Lindemann et al evaluated the airflow characteristics by virtually creating NSPs at 3 different locations (anterior caudal, anterior cranial, and posterior caudal) on a healthy nasal model. Their CFD results show that the anterior caudal NSP led to severe flow changes with high flow velocities, and seemed to be the worst location among all other tested cases.…”

Section: Discussionmentioning

confidence: 99%

“…Using fluid flow properties such as airflow velocity, wall shear stress, and heat flux, CFD has demonstrated utility in assessment of upper respiratory tract and airway reconstructive procedures . However, most previous CFD studies on NSPs addressed virtual perforations of non‐NSP subjects or involved a single NSP patient model . In our previous CFD analysis of nasal airflow in 10 NSP patients we found that the high wall shear stress along the posterior margin of the NSP may lead to symptomatology.…”

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confidence: 95%

Asymptomatic vs symptomatic septal perforations: a computational fluid dynamics examination

Maza

Farag

et al. 2019

Background: A nasal septal perforation (NSP) can lead to frustrating symptoms for some patients while remaining completely asymptomatic for others, without a clear mechanism differentiating them. Methods:We applied individual computed tomography (CT)-based computational fluid dynamics (CFD) to examine the nasal aerodynamics differences between 5 asymptomatic and 15 symptomatic NSP patients. Patients' symptoms were confirmed through interviews, 22-item Sino-Nasal Outcome Test score (asymptomatic, 25 ± 18.8; symptomatic, 53.7 ± 18.2), nasal obstruction symptom evaluation score (asymptomatic, 28.0 ± 32.1; symptomatic, 62.2 ± 32.2), and review of medical history. Results:No statistical differences were found in perforation location, size (asymptomatic, 1.94 ± 1.88 cm 2 ; symptomatic, 1.36 ± 1.44 cm 2 ), nasal resistance (asymptomatic, 0.059 ± 0.012 Pa·s/mL; symptomatic, 0.063 ± 0.022 Pa·s/mL), and computed flow rate shunting across the perforation (asymptomatic, 52.9 ± 30.9 mL/s; symptomatic, 27.4 ± 23.6 mL/s; p > 0.05). However, symptomatic patients had significantly higher wall shear stress (WSS) and heat flux, especially along the posterior perforation margin (WSS, 0.54 ± 0.12 vs 1.15 ± 0.49 Pa, p < 0.001; heat flux, 0.21 ± 0.05 vs 0.37 ± 0.14 W/cm 2 , p < 0.01). A WSS cutoff at 0.72 Pa can separate asymptomatic vs symptomatic NSP with 87% sensitivity and 100% specificity. Flow visualization showed flow peaks toward the posterior margin that may be responsible for the high WSS and heat flux among symptomatic NSPs. Conclusion:This study is the first CFD examination of asymptomatic and symptomatic NSP with regional aerodynamics and stress abnormalities, beyond size or location, being implicated as the mechanism behind the symptomology of NSP. This finding could serve as an objective basis for future personalized treatment decisions and optimization. C 2019 ARS-AAOA, LLC. Key Words: nasal septal perforation; computational fluid dynamics; CT-based modeling; nasal airflow; nasal wall shear stress How to Cite this Article: Li C, Maza G, Farag AA, et al. Asymptomatic vs symptomatic septal perforations: a computational fluid dynamics examination. Int Forum Allergy Rhinol. 2019;9: 883-890.

Numerical simulation of two consecutive nasal respiratory cycles: toward a better understanding of nasal physiology

Gabory

Reville

Baux

et al. 2018