An Overview of Computational Fluid Dynamics Preoperative Analysis of the Nasal Airway

Nasal Airflow Dynamics following LeFort I Advancement in Cleft Nasal Deformities: A Retrospective Preliminary Study

Unilateral cleft lip and palate (UCLP) nasal deformity impacts airflow patterns and pressure distribution, leading to nasal breathing difficulties. This study aims to create an integrated approach using computer-aided design (CAD) and computational fluid dynamics (CFD) to simulate airway function and assess outcomes in nasal deformities associated with unilateral cleft lip and palate (UCLP) after LeFort I osteotomy advancement. Significant alterations were observed in nasal geometry, airflow velocity, pressure dynamics, volumetric flow rate, and nasal resistance postoperatively, indicating improved nasal airflow. The cross-sectional area increased by 26.6%, airflow rate by 6.53%, and nasal resistance decreased by 6.23%. The study offers quantitative insights into the functional impacts of such surgical interventions, contributing to a deeper understanding of UCLP nasal deformity treatment and providing objective metrics for assessing surgical outcome.

Computational analysis of nasal airflow and its alteration by a nasal dilator

Nasal airflow obstruction correlates with several ailments, such as higher patency, increased friction at the mucosal wall or the so-called Little's area, improper air conditioning, and snoring. Nasal dilators are frequently employed, mainly due to their ease of access and use, combined with their non-permanent and non-surgical nature. Their overall efficacy, however, has not been clearly demonstrated so far, with some studies reporting conflicting outcomes, mainly because being based on subjective evaluations. This study employs Computational Fluid Dynamics simulations to analyze the flow inside a real nose, performs an objective assessment of a nasal dilator's effect in terms of airflow and air conditioning, reporting flow paths, friction levels, heat and water fluxes and detailed temperature and humidity distributions. Coincidentally, the studied nose presents a septal deviation, with one nostril being wider than the other. The tubes of the dilator used in both nostrils are identical, as with any standard commercial dilator. Consequently, the dilator widens one nostril, as intended, but results in an obstruction in the other. This allows simultaneously addressing two situations, the nominal function of the dilator, as well as an off-design case. Results indicate a 24 % increase in nasal patency in the design situation. The effect, however, is limited, as quantified by appropriate measures, such as the flow-generated friction at the nose surfaces and the temperature fluxes. Hence, the effect of such a dilator in nominal conditions is perhaps not as large as might be hoped. In the off-design situation, nasal resistance increases by 62 %, an undesirable effect, illustrating the consequences of using an inappropriate dilator.

Algorithm for Nasal Breathing Impairment Evaluation

Assessing patients with complaints of nasal obstruction has traditionally been done by evaluation of the nasal airway looking for fixed or dynamic obstructive locations that could impair nasal airflow. Not infrequently, however, symptoms of nasal obstruction do not match the clinical examination of the nasal airway. Addressing this subset of patients may be a challenge to the surgeon. Evaluation of patients with symptoms of nasal obstruction should include a combination of a patient-reported assessment of nasal breathing and at least one objective method for measuring nasal airflow or nasal airway resistance or dimensions. This will allow distinction between patients with symptoms of nasal obstruction and low airflow or high nasal airway resistance and patients with similar symptoms but whose objective evaluation demonstrates normal nasal airflow or normal airway dimensions or resistance. Patients with low nasal airflow or high nasal airway resistance will require treatment to increase nasal airflow as a necessary step to improve symptoms, whereas patients with normal nasal airflow or nasal airway resistance will require a multidimensional assessment looking for less obvious causes of impaired nasal breathing sensation.

Overview of Nasal Airway and Nasal Breathing Evaluation

Several methods are available for evaluating nasal breathing and nasal airflow, as this evaluation may be made from several different perspectives.Physiologic methods for nasal airway evaluation directly measure nasal airflow or nasal airway resistance, while anatomical methods measure nasal airway dimensions. Subjective methods evaluate nasal breathing through several validated patient-reported scales assessing nasal breathing. Computational fluid dynamics evaluates nasal airflow through the analysis of several physics' variables of the nasal airway.Being familiar to these methods is of utmost importance for the nasal surgeon to be able to understand data provided by the different methods and to be able to choose the combination of evaluation methods that will provide the information most relevant to each clinical situation.

Respiratory Fluid Mechanics of the Effect of Mouth Breathing on High-Arched Palate: Computational Fluid Dynamics Analyses

Computational fluid dynamics (CFD) was introduced into the study of palate growth and development to explain the mechanisms by which mouth breathing affects palate descent from an aerodynamic perspective. Cone beam computed tomography (CBCT) data were used to reconstruct a 3-dimensional model during natural mouth breathing of a volunteer. The model was imported into CFX 19.0 for numerical simulation of nasal breathing, mouth-nasal breathing, and mouth breathing. The pressure in the oronasal cavity was analyzed, and the pressure difference between the oral and nasal surfaces of hard palate under different breathing patterns was calculated. CFD can be used to simulate the stress on the oral and nasal surfaces of the palate under different breathing patterns. The pressure differences and resultant force between the oral and nasal surfaces of the hard palate during nasal inspiration, nasal expiration, mouth-nasal inspiration, mouth-nasal expiration, mouth inspiration, and mouth expiration were 0 Pa, 4 Pa (upward), 9 Pa (upward), 3 Pa (downward), 474 Pa (upward), 263 Pa (downward), respectively, and 87.99 N (upward), 88.03 N (upward), 88.01 N (upward), 88.01 N (upward), 88.05 N (upward), 87.94 N (upward), respectively. Therefore, CFD can be used to investigate the growth and development of the palate. When the volunteer opened his mouth, the pressure difference between the oral and nasal surfaces of the hard palate was about 88 N upward regardless of whether there was airflow in the mouth. The reversal of the direction of the force on the hard palate may be one of the factors affecting its descent of it.

Physical Conditions Prevailing in the Nasal and Maxillary Sinus Cavities Based on Numerical Simulation

Background and Objectives: This paper presents a unique study that links the physical conditions in the nasal passage with conditions that favour the development of bacterial strains and the colonization of the mucous membranes of the nose and paranasal sinuses. The physical parameters considered were air flow, pressure, humidity, and temperature. Materials and Methods: Numerical models of the human nose and maxillary sinus were retrospectively reconstructed from CT images of generally healthy young subjects. The state-of-the-art numerical methods and tools were then used to determine the temperature, humidity, airflow velocity, and pressure at specific anatomical locations. Results: The results were compared with optimal conditions for bacterial growth in the nose and sinuses. Conclusions: Temperature, humidity, air velocity, and pressure were shown to play critical roles in the selection and distribution of microorganisms. Furthermore, certain combinations of physical parameters can favour mucosal colonisation by various strains of bacteria.

Computational Fluid Dynamics Could Enable Individualized Surgical Treatment of Nasal Obstruction (A Preliminary Study)

Passage of nasal airflow during breathing is crucial in achieving accurate diagnosis and optimal therapy for patients with nasal disorders. Computational fluid dynamics (CFD) is the dominant method for simulating and studying airflow. The present study aimed to create a CFD nasal airflow model to determine the major routes of airflow through the nasal cavity and thus help with individualization of surgical treatment of nasal disorders. The three-dimensional nasal cavity model was based on computed tomography scans of the nasal cavity of an adult patient without nasal breathing problems. The model showed the main routes of airflow in the inferior meatus and inferior part of the common meatus, but also surprisingly in the middle meatus and in the middle part of the common nasal meatus. It indicates that the lower meatus and the lower part of the common meatus should not be the only consideration in case of surgery for nasal obstruction in our patient. CFD surgical planning could enable individualized precise surgical treatment of nasal disorders. It could be beneficial mainly in challenging cases such as patients with persistent nasal obstruction after surgery, patients with empty nose syndrome, and patients with a significant discrepancy between the clinical findings and subjective complaints.

[Application of 3D printed nasal vestibular support in the treatment of anterior nostril stenosis]

Objective:To evaluate the efficacy of 3D printed nasal vestibular support on the recovery of nasal ventilation function and nostril shape after nostril stenosis treatment. Methods:Thirty-eight patients with unilateral traumatic nasal vestibular stenosis were selected and treated with 3D printed nasal vestibular support after operation. Subjective evaluation indicators, objective nostril local morphological and structural parameters, and nasal airflow dynamics parameters by numerical simulation were used. To evaluate the nostril morphological and nasal functional recovery after treatment. Results:The subjective nasal congestion and nostril symmetry satisfaction VAS scores of the patients after nasal vestibular support treatment were improved to varying degrees compared with those before surgery; The nostril morphological parameters showed that the Δlong-axis ratio and Δ short-axis ratio were significantly decreased after nasal vestibular support therapy （0.09±0.09 and 0.16±0.13） compared with those before surgery（0.21±0.20 and 0.28±0.21） respectively（P<0.01）. And the cross-sectional area of the nasal valve on the stenotic side nasal cavity increased from（0.40±0.27） cm² before operation to （0.71±0.26） cm² after treatment（P<0.01）; The nasal resistance on the stenosis side nasal cavity also decreased from （0.036±0.024） Pa·s/mL before operation to （0.022±0.008） Pa. s/mL after treatment（P<0.01）, and the total nasal resistance was decreased from （0.033±0.02） Pas/mL before operation to （0.021±0.007）Pa. s/mL after treatment（P<0.01） ; It also showed that NWE（nasal warming efficiency） and NHE（nasal humidification efficiency） on the stenotic side nasal cavity were significantly decreased after nasal vestibular support therapy（[95.92±2.8]% and [94.55±4.17]%） compared with those before surgery （[97.94±1.97 ]% and [96.19±2.94]%） respectively（P<0.01）. Conclusion:The 3D printed nasal vestibular support for postoperative support treatment on patients with anterior nostril stenosis can reflect the advantages of personalized treatment and allow patients to obtain satisfactory results, and the use of individually designed 3D printed nasal vestibular support can make the shape of anterior nostrils and nasal cavity normal ventilation function recover well, its clinical application prospect is worth looking forward to.

Piezo-assisted Turbinoplasty Versus Partial Turbinectomy in External Septorhinoplasty: A Prospective Comparative Study in 100 Patients

OBJECTIVES

The purpose of this study was to compare the outcome of the piezo-assisted turbinoplasty with a partial turbinectomy technique in the treatment of chronic nasal obstruction due to inferior turbinate enlargement.

STUDY DESIGN

This is a prospective randomized single-center study in a cohort of 100 consecutive patients which underwent external septorhinoplasty and concomitant hybrid type of turbinoplasty.

METHODOLOGY

Patients were randomly assigned into two groups. The first group included 50 patients who underwent piezo-assisted outfracturing of the inferior turbinates in combination with bipolar coagulation. The second group included 50 patients who underwent a treatment based on turbinate bipolar coagulation and partial resection of the inferior border of the turbinate. The severity of nasal obstruction was measured in both patient groups with a patient-related outcome questionnaire (NOSE) and objective measures (anterior rhinomanometry and acoustic rhinometry). Assessments were conducted prior to surgery and 3 months after the surgery.

RESULTS

There was a significant improvement in the values of the NOSE questionnaire with no relevant difference between the two study groups. Acoustic rhinometry and rhinomanometry also showed no statistically significant differences between the two study groups. No differences in postoperative healing were found, and postoperative complications were comparable low in both groups. However, the piezo-assisted procedure was quicker to perform with only minimal bleeding.

CONCLUSION

During septorhinoplasty, the combination of thermo-coagulation with piezo-assisted turbinoplasty was as efficient as with partial turbinectomy to establish normal nasal breathing.

LEVEL OF EVIDENCE III

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