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Objective(s): Chronic rhinosinusitis (CRS) is common and often requires surgical intervention. Surgical failure may lead to persistent symptoms and recalcitrant disease, often secondary to synechiae between the middle turbinate (MT) and lateral nasal wall. Synechiae prevention techniques have been extensively investigated, however evidence for the effect of synechiae on sinonasal physiology is lacking. We aimed to model the effects of MT synechiae on a post-functional endoscopic sinus surgery (FESS) sinonasal cavity using computational fluid dynamics (CFD)., Methods: DICOM data from a CT-sinus of a healthy 25-year-old female was segmented to create a three-dimensional model. Virtual surgery was performed to simulate a "full-house" FESS procedure. Multiple models were created, each with a single unilateral virtual MT synechia of varying extent. CFD analysis was performed on each model and compared with a post-FESS control model without synechiae. Airflow velocity, humidity and mucosal surface and air temperature values were calculated., Results: All synechiae models demonstrated aberrant downstream sinonasal airflow. There was reduced ventilation of the ipsilateral frontal, ethmoid and sphenoid sinuses, with a concentrated central "jet" in the middle meatus region. Effects were proportionate to the size of synechiae. The impact on bulk inspired airflow was negligible., Conclusion: Post-FESS synechiae between the MT and lateral nasal wall significantly disrupt local downstream sinus ventilation and nasal airflow. These findings may explain the persistent symptoms seen in post-FESS CRS patients with MT synechiae, reinforcing the importance of prevention and adhesiolysis. Larger cohort studies with multiple models of actual post-FESS patients with synechiae are required to validate these findings., Competing Interests: Declaration of Competing Interest The authors of this manuscript have no conflicts of interest to disclose., (Copyright © 2023. Published by Elsevier B.V.)

Nasal adhesions are a known postoperative complication following surgical procedures for nasal airway obstruction (NAO); and are a common cause of surgical failure, with patients often reporting significant NAO, despite relatively minor adhesion size. Division of such nasal adhesions often provides much greater relief than anticipated, based on the minimal reduction in cross-sectional area associated with the adhesion. The available literature regarding nasal adhesions provides little evidence examining their quantitative and qualitative effects on nasal airflow using objective measures. This study examined the impact of nasal adhesions at various anatomical sites on nasal airflow and mucosal cooling using computational fluid dynamics (CFD). A high-resolution CT scan of the paranasal sinuses of a 25-year-old, healthy female patient was segmented to create a three-dimensional nasal airway model. Virtual nasal adhesions of 2.5 mm diameter were added to various locations within the nasal cavity, representing common sites seen following NAO surgery. A series of models with single adhesions were created. CFD analysis was performed on each model and compared with a baseline no-adhesion model, comparing airflow and heat and mass transfer. The nasal adhesions resulted in no significant change in bulk airflow patterns through the nasal cavity. However, significant changes were observed in local airflow and mucosal cooling around and immediately downstream to the nasal adhesions. These were most evident with anterior nasal adhesions at the internal valve and anterior inferior turbinate. Postoperative nasal adhesions create local airflow disruption, resulting in reduced local mucosal cooling on critical surfaces, explaining the exaggerated perception of nasal obstruction. In particular, anteriorly located adhesions created greater disruption to local airflow and mucosal cooling, explaining their associated greater subjective sensation of obstruction., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Nasal irrigation is a widely recognized treatment for several sinonasal diseases. However, there is a lack of clear evidence-based guidelines for optimal irrigation delivery to improve lavage and topical drug delivery. This study uses computational fluid dynamics (CFD) to assess the effects of different head tilt positions on sinonasal coverage, residence time and shear stresses in squeeze-bottle nasal irrigation. A sinonasal cavity computational model was constructed from a high-resolution CT scan of a healthy, 25-year-old Asian female. The Volume of Fluid method was used to track the interface between the two immiscible fluids (air and water). The direction of gravity was varied to simulate different head tilt-positions (0° Straight, 45° Forward, 45° Left, 45° Right and 45° Backward) during nasal irrigation with 150 mL liquid via a squeeze bottle through the left nostril for 2 s with a 0.1 s acceleration/deceleration time. The results showed that the 45° backward head tilt position was the most effective in delivering irrigation to the ethmoid, frontal and sphenoid sinuses. Altering head tilt had minimal impact on irrigation delivery to the maxillary sinuses. Maximum wall shear stresses seen in localized areas of the sinus mucosa varied significantly with different head tilt angles. However, the difference in mean wall shear stress on the sinus surfaces was marginal with changing head tilt position. The findings suggest that an optimized head tilt position can be identified to improve liquid irrigation to targeted sinuses, as per treatment requirements (lavage and topical drug delivery)., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Nasal saline irrigation is frequently utilised in rhinosinusitis management, and after nasal and sinus surgery. Nasal saline irrigation improves mucociliary transport and assists inflammatory mediator and post-surgical debris removal. The aim of this study was to assess the influence different head positions, irrigation inflow nostril, and the nasal cycle have on Neti pot nasal saline volume filling within the nasal passages and maxillary sinuses. Computational fluid dynamics modelling using anatomically correct nasal geometry found only minor difference in nasal cavity volume filling with inflow from either side of the nose however both head position and inflow direction were both found to have a major influence on maxillary sinus volume filling. Computational modelling flow velocity results at the nasopharynx were validated using particle image velocimetry. It was also found that directing irrigation inflow into the patent side of the nose while in the head-back position achieved the highest volume filling of both maxillary sinuses., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Nasal saline irrigation is frequently utilised in allergic rhinitis and rhinosinusitis management, and after nasal and sinus surgery. Anatomical modelling, clinical and computational studies guide treatment optimisation. This review offers a comprehensive summary of the modelling methodologies used in previous nasal irrigation studies by undertaking a systematic analysis of anatomical, clinical and computational investigations that assessed nasal saline irrigation using Medline, EMBASE, and Cochrane Review databases. Both procedural and assessment methods were reviewed. It was found that all twenty-four publications reviewed did not discuss the influence of the nasal cycle on internasal geometry and nasal resistance. Cadaver studies misrepresent in vivo nasal geometry. Irrigation pressure and shear forces, which could influence mucociliary transport and postoperative cleaning, were not evaluated. Previous studies focus on irrigation coverage and have not considered the nasal cycle which influences unilateral nasal resistance and thus pressure/ flow relationships and may also increase nasal air-locking. New computational fluid dynamic models could better inform nasal irrigation clinical practice., Competing Interests: Declaration of Competing Interest None of the authors have conflicts of interest to declare., (Copyright © 2019 Elsevier B.V. All rights reserved.)