Assessment of septal deviation effects on nasal air flow: A computational fluid dynamics model

Anatomy and Physiology of the Nasal Valves

The nasal valves are not simple, 2-dimensional cross-sections but rather a complex, 3-dimensional, collapsible, and heterogeneous structure. Historically, the internal nasal valve (INV) is defined by the septum medially, the caudal margin of the upper lateral cartilage laterally, and the inferior turbinate inferiorly. Typically located 1.3 cm deep into the nasal cavity, the INV angle delineated by the upper lateral cartilage and septum typically measures 10° to 15° in the Caucasian population. As computational methods reveal new insights into nasal valve function, a new conceptual framework is needed to guide rhinoplasty surgical decision-making.

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.

Computational Rhinology: Unraveling Discrepancies between In Silico and In Vivo Nasal Airflow Assessments for Enhanced Clinical Decision Support

Computational rhinology is a specialized branch of biomechanics leveraging engineering techniques for mathematical modelling and simulation to complement the medical field of rhinology. Computational rhinology has already contributed significantly to advancing our understanding of the nasal function, including airflow patterns, mucosal cooling, particle deposition, and drug delivery, and is foreseen as a crucial element in, e.g., the development of virtual surgery as a clinical, patient-specific decision support tool. The current paper delves into the field of computational rhinology from a nasal airflow perspective, highlighting the use of computational fluid dynamics to enhance diagnostics and treatment of breathing disorders. This paper consists of three distinct parts-an introduction to and review of the field of computational rhinology, a review of the published literature on in vitro and in silico studies of nasal airflow, and the presentation and analysis of previously unpublished high-fidelity CFD simulation data of in silico rhinomanometry. While the two first parts of this paper summarize the current status and challenges in the application of computational tools in rhinology, the last part addresses the gross disagreement commonly observed when comparing in silico and in vivo rhinomanometry results. It is concluded that this discrepancy cannot readily be explained by CFD model deficiencies caused by poor choice of turbulence model, insufficient spatial or temporal resolution, or neglecting transient effects. Hence, alternative explanations such as nasal cavity compliance or drag effects due to nasal hair should be investigated.

Value of Opening the Middle Meatus in Patients With Nasal Airway Obstruction

OBJECTIVES

While surgeries to correct the anatomical malformations that cause nasal airway obstruction (NAO) are generally successful, the outcomes of such procedures are often unsatisfactory. The aim of the present study was to assess the value of opening the middle meatus in patients with NAO.

METHODS

Thirty-four patients with nasal obstruction due to nasal septal deviation were included in this study. After randomization, the middle meatus was either opened or not opened during septoplasty. The patients were evaluated through pre- and postoperative rhinomanometry and acoustic rhinometry. The Visual Analog Scale (VAS) scores of subjective symptoms along with responses to the 20-item Sinonasal Outcome Test (SNOT-20) were obtained before surgery and three months after surgery.

RESULTS

The VAS scores and SNOT-20 responses improved significantly in both groups after surgery. The effective treatment rate based on the nasal congestion score (NCS) was 64.7% in the single group (septoplasty alone) and 100% in the combined group (septoplasty in conjunction with opening the middle meatus), and the difference was statistically significant (P = .018). In both groups, surgery significantly improved nasal flow, resistance, minimal cross-sectional area, cross-sectional area 6 cm (CA6) from the anterior nostril and nasal volume. Nasal volume and CA6 after surgery were statistically different between the 2 groups (P = .004 and .019, respectively).

CONCLUSIONS

Opening the middle meatus may further improve the subjective perception of patency on the basis of septoplasty.

Association between nasal septum deviation and transverse maxillary development: A retrospective cross-sectional study

INTRODUCTION

The few studies investigating the relationship between nasal septum deviation (NSD) and maxillary development, using different assessment methods and the age of subjects, reported contradicting results.

METHODS

The association between NSD and transverse maxillary parameters was analyzed using 141 preorthodontic full-skull cone-beam computed tomography scans (mean age, 27.4 ± 9.01 years). Six maxillary, 2 nasal, and 3 dentoalveolar landmarks were measured. The intraclass correlation coefficient was used to assess intrarater and interrater reliability. The correlation between NSD and transverse maxillary parameters was analyzed using the Pearson correlation coefficient. Each transverse maxillary parameter was compared among 3 groups of different degrees of severity using the analysis of variance test. Transverse maxillary parameters were also compared between the more and less deviated nasal septum sides using the independent t test.

RESULTS

A correlation between deviated septal width and palatal arch depth (r = 0.2, P <0.013) and significant differences in palatal arch depth (P <0.05) among 3 NSD severity groups classified with deviated septal width was noted. There was no correlation between septal deviated angle and transverse maxillary parameters and no significant difference for transverse maxillary parameters among the 3 groups of NSD severity classified by septal deviated angle. No significant difference in transverse maxillary parameters was found when comparing the more and the less deviated sides.

CONCLUSIONS

This study suggests that NSD can affect palatal vault morphology. The magnitude of NSD may be a factor associated with transverse maxillary growth disturbance.

Soft tissues influence nasal airflow in diapsids: Implications for dinosaurs

The nasal passage performs multiple functions in amniotes, including olfaction and thermoregulation. These functions would have been present in extinct animals as well. However, fossils preserve only low-resolution versions of the nasal passage due to loss of soft-tissue structures after death. To test the effects of these lower resolution models on interpretations of nasal physiology, we performed a broadly comparative analysis of the nasal passages in extant diapsid representatives, e.g., alligator, turkey, ostrich, iguana, and a monitor lizard. Using computational fluid dynamics, we simulated airflow through 3D reconstructed models of the different nasal passages and compared these soft-tissue-bounded results to similar analyses of the same airways under the lower-resolution limits imposed by fossilization. Airflow patterns in these bony-bounded airways were more homogeneous and slower flowing than those of their soft-tissue counterparts. These data indicate that bony-bounded airway reconstructions of extinct animal nasal passages are far too conservative and place overly restrictive physiological limitations on extinct species. In spite of the diverse array of nasal passage shapes, distinct similarities in airflow were observed, including consistent areas of nasal passage constriction such as the junction of the olfactory region and main airway. These nasal constrictions can reasonably be inferred to have been present in extinct taxa such as dinosaurs.

Impact of the Location of Nasal Septal Deviation on the Nasal Airflow and Air Conditioning Characteristics

The location of nasal septal deviation (NSD) directly impacts nasal physiology. The objective is to examine, using computational fluid dynamics (CFD), the difference in the airflow and air conditioning characteristics according to the location of NSD. Twenty patients with septal deviation were divided into two: 10 caudal septal deviation (CSD) and 10 posterior septal deviation (PSD). Physiological variables were compared and numerical models for nasal cavity were created with CT scans. Cases with CSD had distinctive features including restricted airflow partition, larger nasal resistance, and decreased surface heat flux in the more obstructed side (MOS), and lower humidity and air temperature in the lesser obstructed side (LOS). Physiological differences were observed according to the location of septal deviation, CSD cases exhibit significantly more asymmetric airflow characteristics and air conditioning capacity between LOS and MOS.

Improvements in airflow characteristics and effect on the NOSE score after septoturbinoplasty: A computational fluid dynamics analysis

Septoturbinoplasty is a surgical procedure that can improve nasal congestion symptoms in patients with nasal septal deviation and inferior turbinate hypertrophy. However, it is unclear which physical domains of nasal airflow after septoturbinoplasty are related to symptomatic improvement. This work employs computational fluid dynamics modeling to identify the physical variables and domains associated with symptomatic improvement. Sixteen numerical models were generated using eight patients' pre- and postoperative computed tomography scans. Changes in unilateral nasal resistance, surface heat flux, relative humidity, and air temperature and their correlations with improvement in the Nasal Obstruction Symptom Evaluation (NOSE) score were analyzed. The NOSE score significantly improved after septoturbinoplasty, from 14.4 ± 3.6 to 4.0 ± 4.2 (p < 0.001). The surgery not only increased the airflow partition on the more obstructed side (MOS) from 31.6 ± 9.6 to 41.9 ± 4.7% (p = 0.043), but also reduced the unilateral nasal resistance in the MOS from 0.200 ± 0.095 to 0.066 ± 0.055 Pa/(mL·s) (p = 0.004). Improvement in the NOSE score correlated significantly with the reduction in unilateral nasal resistance in the preoperative MOS (r = 0.81). Also, improvement in the NOSE score correlated better with the increase in surface heat flux in the preoperative MOS region from the nasal valve to the choanae (r = 0.87) than in the vestibule area (r = 0.63). Therefore, unilateral nasal resistance and mucous cooling in the preoperative MOS can explain the perceived improvement in symptoms after septoturbinoplasty. Moreover, the physical domain between the nasal valve and the choanae might be more relevant to patient-reported patency than the vestibule area.

Prospective cohort study on short-term evaluation of septoplasty as early management of naso-septal fractures - A correlation of clinical outcomes with computational fluid dynamic parameters

PURPOSE

Post-traumatic deviated nasal septum (PTDNS) leads to impaired breathing and poor esthetics. The aim of this study was to assess treatment outcomes of early septoplasty for correction of PTDNS and correlate it with computational fluid dynamic (CFD) parameters.

METHODS

This prospective cohort study included patients who underwent early septoplasty for PTDNS. Outcome variables were clinical (pain, nasal symmetry, and nasal obstruction) and computational (velocity, pressure, wall shear stress and Reynold's number). The cohort consisted of two groups: patients with history of closed reduction for nasal fractures (CR) and patients without (NCR). The primary outcome measure was response to treatment. Correlation between clinical and computational parameters, and influence of closed reduction on septoplasty outcomes were the secondary and tertiary outcomes, respectively. Descriptive and inferential statistics were performed to analyze data. Level of significance was fixed at 5% (α = 0.05).

RESULTS

The sample included 12 patients, of which 5 underwent CFD analysis. Pain score reduced from a pre-operative mean of 7.3 to 0.5 post-operatively (p<0.001). All patients demonstrated reduction of nasal obstruction (p<0.001) and deviation (p<0.001) post-operatively. CFD analysis revealed post-operative reduction of velocity (p = 0.005) and Reynold's number (p = 0.007), with positive correlation between nasal obstruction and CFD parameters. Though patients in the CR group demonstrated reduced nasal deviation and obstruction before septoplasty, as compared to the NCR group, their outcomes were comparable following septoplasty.

CONCLUSION

Early septoplasty improves functional and esthetic outcomes in patients with PTDNS. CFD simulation is a predictable method to objectively evaluate nasal function.

Changes in inflammatory biomarkers in the nasal mucosal secretion after septoplasty

Deviated nasal septum (DNS) is suggested to be associated with nonspecific inflammation of the nasal mucosa. The authors hypothesized septoplasty may reduce nasal mucosal inflammation, therefore the authors aimed to measure various inflammatory biomarkers in the nasal secretion following septoplasty. Prospectively, 17 patients undergoing elective septoplasty were included. Symptomatic changes after septoplasty were evaluated with Sino-nasal Outcome Test (SNOT-22) and Nasal obstruction symptom evaluation (NOSE) scores. Using acoustic rhinometry, changes of the nasal airway volume were measured. Nasal secretion was collected within 2 weeks and 3 months before and after septoplasty, respectively. The inflammatory biomarker high-mobility group box 1 (HMGB1) and vasoactive intestinal peptide (VIP), and inflammatory cytokines including tumor necrosis factor α (TNF α), interferon γ (IFN-γ), interleukin-4 (IL-4), eotaxin-1, and regulated upon activation, normal T cell expressed and presumably secreted (RANTES) were quantified in the nasal secretion by enzyme-linked immunosorbent assays or multiplex bead array assays. The patients' mean age was 30.5 ± 6.8 (ranging from 19 to 43), consisting of 15 male and 2 female patients. The median SNOT-22 and NOSE scores changed from 54 to 14 and 78 to 15, respectively, both showing a significant decrease. In acoustic rhinometry, nasal cavity volume of convex side significantly increased after septoplasty, whereas significant discrepancy of nasal airway volume between concave and convex sides became insignificant. No significant difference was noted both before and after septoplasty between the concave and convex sides in all seven biomarkers. The HMGB1, RANTES, IL-4, and TNF-α concentrations following septoplasty showed significant decrease in 34 nasal cavities of 17 patients (all p < 0.05). However, when the 17 concave and 17 convex sides were analyzed separately, the significant reduction in four biomarkers were only significant in the concave sides (all p < 0.05), but not significantly reduced in convex sides. Septoplasty may have benefited not only in normalizing the nasal airflow and symptom improvement, but also in nonspecific inflammation attenuation in the nasal airway.

Analysis of predisposing factors in unilateral maxillary sinus fungal ball: the predictive role of odontogenic and anatomical factors

BACKGROUND

The pathogenesis of maxillary sinus fungal ball (MSFB) is explained by aerogenic and odontogenic factors. We evaluated the predisposing factors, including intranasal anatomical and dental factors for increased diagnostic accuracy.

METHODOLOGY

In this study, 117 patients who underwent endoscopic sinus surgery for unilateral MSFB were included. Preoperative computed tomography (CT) scans were used to analyze the presence of anatomical variations (anterior and posterior nasal septal deviation (NSD), concha bullosa (CB), infraorbital cell (haller cell), paradoxical middle turbinate, everted uncinate process and MS size). Dental factors including history of dental procedures and findings on CT scans were reviewed.

RESULTS

Anterior and posterior NSD toward non-affected side were significantly associated with the presence of FB. The presence of CB and infraorbital cell was higher in the non-affected side rather than in the lesion side. Compared to non-affected MS, FB-presence MS was shallower and had a larger height to depth ratio. The presence of dental history was significantly higher on FB-presence MS than non-affected MS. In multivariable analysis, posterior NSD toward non-affected side, dental history increased the aOR of MSFB, while the presence of CB and infraorbital cell decreased the aOR of MSFB.

CONCLUSIONS

The occurrence of MSFB seems to be associated with ipsilateral odontogenic factors, followed by anatomic variations including posterior NSD toward non-affected side and absence of CB and infraorbital cell.

Instillation of a Dry Powder in Nasal Casts: Parameters Influencing the Olfactory Deposition With Uni- and Bi-Directional Devices

Nose-to-brain delivery is a promising way to reach the central nervous system with therapeutic drugs. However, the location of the olfactory region at the top of the nasal cavity complexifies this route of administration. In this study, we used a 3D-printed replica of a nasal cavity (a so-called “nasal cast”) to reproduce in vitro the deposition of a solid powder. We considered two different delivery devices: a unidirectional device generating a classical spray and a bidirectional device that relies on the user expiration. A new artificial mucus also coated the replica. Five parameters were varied to measure their influence on the powder deposition pattern in the olfactory region of the cast: the administration device, the instillation angle and side, the presence of a septum perforation, and the flow rate of possible concomitant inspiration. We found that the unidirectional powder device is more effective in targeting the olfactory zone than the bi-directional device. Also, aiming the spray nozzle directly at the olfactory area is more effective than targeting the center of the nasal valve. Moreover, the choice of the nostril and the presence of a perforation in the septum also significantly influence the olfactory deposition. On the contrary, the inspiratory flow has only a minor effect on the powder outcome. By selecting the more efficient administration device and parameters, 44% of the powder can reach the olfactory region of the nasal cast.

Evaluation of effect of septoplasty on nasal mucosal dryness using intranasal Schirmer test

BACKGROUND

Septal deviation causes the air entering the nose to encounter resistance and leads to turbulent flow formation by disrupting laminar air flow. In the literature, the Schirmer test has been recommended to evaluate the moistening of the nasal mucosa.

AIMS/OBJECTIVES

The purpose of this study was to evaluate the degree of nasal humidification using the intranasal schirmer test in patients with septal deviation and to reveal changes in mucosal dryness and humidity in both nasal cavities following septoplasty surgery.

MATERIAL AND METHODS

Fifty-three patients with septal deviation detected at endoscopic rhinoscopic examination and scheduled for surgery were enrolled. Schirmer test was performed twice, at a one-month interval, pre- and postoperatively and test records were compared.

RESULTS

The Schirmer test value for the deviated side of the septum was significantly lower than that for the contralateral side, for both nasal cavities. Schirmer test values increased significantly on the side of the septal deviation compared to the preoperative values.

CONCLUSIONS AND SIGNIFICANCE

Septoplasty surgery performed for septal deviation significantly and reduces nasal mucosa dryness so increases Schirmer test results on the deviated side. We attribute this to septal deviation impairing air flow in the nasal cavity and causing nasal mucosa dryness.

Wet surface wall model for latent heat exchange during evaporation

Air conditioning is a dual heat and mass transfer process, and the human nasal cavity achieves this through the mucosal wall surface, which is supplied with an energy source through the sub-epithelial network of capillaries. Computational studies of air conditioning in the nasal cavity have included temperature and humidity, but most studies solved these flow parameters separately, and in some cases, a constant mucosal surface temperature was used. Recent developments demonstrated that both heat and mass transfer need to be modeled. This work expands on existing modeling efforts in accounting for the nasal cavity's dual heat and mass transfer process by introducing a new subwall model, given in the Supplementary Materials. The model was applied to a pipe geometry, and a human nasal cavity was recreated from CT-scans, and six inhalation conditions were studied. The results showed that when the energy transfer from the latent heat of evaporation is included, there is a cooling effect on the mucosal surface temperature.

Paranasal Sinus Fungus Ball, Anatomical Variations and Dental Pathologies: Is There Any Relation?

Objective:

The purpose of this study was to investigate the relationship between anatomical variations and the fungus ball (FB), and the association between odontogenic etiologies and the maxillary sinus FB.

Methods:

We analyzed the clinical records of 66 patients who underwent endoscopic sinus surgery for FB. The anatomical variations determined were nasal septal deviation (NSD) and direction, presence of Onodi and Haller cell, concha bullosa and lateral recess of the sphenoid sinus. Further, dental X-ray records were reviewed to detect any possible odontogenic etiologies in patients with maxillary sinus FBs.

Results:

There were 41 female and 25 male patients. Positive fungal culture was found in 60 patients (91%) and the causative fungus was Aspergillus species in all cases. The correlation between NSD and localization of the maxillary sinus FB was statistically significant (p=0.0409). Maxillary sinus FB was more common on the concave side of the NSD. Presence of dental pathologies was significantly associated with maxillary sinus FB compared to the healthy side (p=0.0011). For sphenoid sinus FB, NSD was detected in a similar number for both the affected and unaffected side and there were no significant correlations (p>0.05). However, the relationship between sphenoid sinus FB and presence of lateral recess was significant (p=0.0262).

Conclusion:

Our study revealed that the maxillary sinus FB was more common on the concave side of the deviated septum. Also, dental pathologies or a presence of dental treatment history were associated with maxillary sinus FB.

Septal deviation in the nose of the longest faced crocodylian: A description of nasal anatomy and airflow in the Indian gharial (Gavialis gangeticus) with comments on acoustics

The remarkably thin rostrum in the Indian gharial (Gavialis gangeticus) imparts challenges to nasal physiology. Competition for space in the slim jaws necessitates a thin nasal septum, leaving this taxon susceptible to nasal passage abnormalities such as septal deviation. Here we describe the nasal anatomy of gharials based on multiple individuals including one that showcases an extreme instance of nasal septum deviation. We found that gharials have both confluent nostrils and choanae, which may be important for their unique nasal acoustics. The deviated nasal septum in the female showed distinct waviness that affected the nasal passages by alternately compressing them. We performed a computational fluid dynamic analysis on the nasal passages to visualize the effects of septal deviation on airflow. Our analysis found the deviated septum increased nasal resistance and wall shear stress during respiration, resulting in unequal distribution of the air field between both sides of the nasal passage. Our findings indicate that gharials-and potentially other longirostrine crocodylians-may be particularly susceptible to septal deviations. Lastly, we observed pterygoid bullae to be present in both sexes, though their morphology differed. Airflow in the male pterygoid bullae produced a Bernoulli effect which may be responsible for the unique "pop" sounds recorded in this species.

The importance of pre-formulation studies and of 3D-printed nasal casts in the success of a pharmaceutical product intended for nose-to-brain delivery

This review aims to cement three hot topics in drug delivery: (a) the pre-formulation of new products intended for nose-to-brain delivery; (b) the development of nasal casts for studying the efficacy of potential new nose-to-brain delivery systems at the early of their development (pre-formulation); (c) the use of 3D printing based on a wide variety of materials (transparent, biocompatible, flexible) providing an unprecedented fabrication tool towards personalized medicine by printing nasal cast on-demand based on CT scans of patients. This review intends to show the links between these three subjects. Indeed, the pathway selected to administrate the drug to the brain not only influence the formulation strategies to implement but also the design of the cast, to get the most convincing measures from it. Moreover, the design of the cast himself influences the choice of the 3D-printing technology, which, in its turn, bring more constraints to the nasal replica design. Consequently, the formulation of the drug, the cast preparation and its realisation should be thought of as a whole and not separately.

Aerodynamics Analysis of the Impact of Nasal Surgery on Patients with Obstructive Sleep Apnea and Nasal Obstruction

OBJECTIVE

The purpose of this study was to evaluate the effects of nasal surgery on airflow characteristics in patients with obstructive sleep apnea (OSA) by comparing the alterations of airflow characteristics within the nasal and palatopharyngeal cavities.

METHODS

Thirty patients with OSA and nasal obstruction who underwent nasal surgery were enrolled. A pre- and postoperative 3-dimensional model was constructed, and alterations of airflow characteristics were assessed using the method of computational fluid dynamics. The other subjective and objective clinical indices were also assessed.

RESULTS

By comparison with the preoperative value, all postoperative subjective symptoms statistically improved (p < 0.05), while the Apnea-Hypopnea Index (AHI) changed little (p = 0.492); the postoperative airflow velocity and pressure in both nasal and palatopharyngeal cavities, nasal and palatopharyngeal pressure differences, and total upper airway resistance statistically decreased (all p < 0.01). A significant difference was derived for correlation between the alteration of simulation metrics with subjective improvements (p < 0.05), except with the AHI (p > 0.05).

CONCLUSION

Nasal surgery can decrease the total resistance of the upper airway and increase the nasal airflow volume and subjective sleep quality in patients with OSA and nasal obstruction. The altered airflow characteristics might contribute to the postoperative reduction of pharyngeal collapse in a subset of OSA patients.

Numerical Simulation of Nasal Airflow Aerodynamics, and Warming and Humidification in Models of Clival Chordoma Pre and Post-Endoscopic Endonasal Surgery

OBJECTIVES

To study the effect of endoscopic endonasal surgery on nasal function for the treatment of clival chordoma.

METHODS

Pre and post-operative computed tomography (CT) scans of a case of chordoma treated with an endoscopic endonasal approach (EEA) were collected retrospectively, and models of the nasal cavity were reconstructed so that a subsequent numerical simulation of nasal airflow characteristics, warming, and humidification could be conducted.

RESULTS

Middle turbinectomy resulted in redistribution of airflow within the nasal cavity, and the most significant changes occurred in the middle section. Consistent with the results of airflow evaluation, it was found that the change in nasal anatomical structure significantly reduced warming and humidification. Nasal humidification decreased substantially when postoperative loss of mucosa was taken into consideration. The H₂O mass fraction of pharynx in inspiration phase were significantly correlated with airway surface-to-volume ratio (SVR).

CONCLUSIONS

The EEA for chordoma significantly affected nasal function. Attention should be paid to the protection of nasal structure and the associated mucosa.

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

Evaluation of the nasal airway is crucial for every patient with symptoms of nasal obstruction as well as for every patient with other nasal symptoms. This assessment of the nasal airway comprises clinical examination together with imaging studies, with the correlation between findings of this evaluation and symptoms reported by the patient being based on the experience of the surgeon. Measuring nasal airway resistance or nasal airflow can provide additional data regarding the nasal airway, but the benefit of these objective measurements is limited due to their lack of correlation with patient-reported evaluation of nasal breathing. Computational fluid dynamics (CFD) has emerged as a valuable tool to assess the nasal airway, as it provides objective measurements that correlate with patient-reported evaluation of nasal breathing. CFD is able to evaluate nasal airflow and measure variables such as heat transfer or nasal wall shear stress, which seem to reflect the activity of the nasal trigeminal sensitive endings that provide sensation of nasal breathing. Furthermore, CFD has the unique capacity of making airway analysis of virtual surgery, predicting airflow changes after trial virtual modifications of the nasal airway. Thereby, CFD can assist the surgeon in deciding surgery and selecting the surgical techniques that better address the features of each specific nose. CFD has thus become a trend in nasal airflow assessment, providing reliable results that have been validated for analyzing airflow in the human nasal cavity. All these features make CFD analysis a mainstay in the armamentarium of the nasal surgeon. CFD analysis may become the gold standard for preoperative assessment of the nasal airway.

Rapid Maxillary Expansion Has a Beneficial Effect on the Ventilation in Children With Nasal Septal Deviation: A Computational Fluid Dynamics Study

Nasal septal deviation (NSD) is one of the most common nasal diseases. Different from common clinical examination methods, computational fluid dynamics (CFD) can provide visual flow information of the nasal cavity. The dimension and volume of the nasal cavity are easily affected by rapid maxillary expansion (RME). The purpose of this study was to use CFD to evaluate the effect of RME on the aerodynamics of the nasal cavity in children with maxillary transverse deficiency and NSD. Computational fluid dynamics was implemented after 3D reconstruction based on the CBCT of 15 children who have completed RME treatment. After treatment, the volume increases in the nasal cavity, nasopharynx, oropharynx, and pharynx were not statistically significant. The wall shear stress of the nasal cavity after RME, 1.749 ± 0.673 Pa, was significantly lower than that before RME, 2.684 ± 0.919 Pa. Meanwhile, the maximal negative pressure in the pharyngeal airway during inspiration was smaller after RME (-31.058 Pa) than before (-48.204 Pa). This study suggests that RME has a beneficial effect on nasal ventilation. The nasal airflow became more symmetrical in the bilateral nasal cavity after RME. Pharyngeal resistance decreased with the reduction in nasal resistance and the increase in the volume of oropharynx after RME.

Evaluation of airflow characteristics before and after septoplasty in unilateral cleft patients with a deviated nasal septum: a computational fluid dynamics study

The aim of this study was to evaluate changes in airflow characteristics before and after septoplasty in unilateral cleft lip and palate (UCLP) patients using computational fluid dynamics (CFD) models. The study was designed as a prospective cohort study involving pre- and postoperative computed tomography data from 12 UCLP patients with a deviated nasal septum who underwent septoplasty. CFD analysis of nasal airflow was conducted to study changes in velocity, pressure, volume, nasal resistance, and wall shear stress of the nasal domain before and after surgery. The study results demonstrated a statistically significant difference in pressure drop after septoplasty: median 116.10Pa (interquartile range (IQR) 749.02Pa) preoperative compared with 43.39Pa (IQR 349.01Pa) postoperative (P= 0.004). Maximum wall shear stress was found to be approximately three times lower after septoplasty: median 6.15 Pa (IQR 1908.62 Pa) preoperative versus median 2.51 Pa (IQR 540.06 Pa) postoperative (P=0.002). Changes in nasal resistance were also found to be statistically significant: median 460.59 Pa·s/l (IQR 1946.99 Pa·s/l) preoperative versus median 166.61 Pa·s/l (IQR 694.08 Pa·s/l) postoperative (P=0.04). These values demonstrate significant changes in flow dynamics after surgery indicative of a more uniform airflow pattern and stabilization of the nasal mucosa.

Magnetic resonance imaging evaluation of the distribution of spray and irrigation devices within the sinonasal cavities

BACKGROUND

Optimizing intranasal distribution and retention of nasal sprays is essential in the management of patients with chronic rhinosinusitis (CRS), including those that have had functional endoscopic sinus surgery (FESS). Despite multiple existing distribution studies, there remains a need for a technique that allows regionalization of particle deposition within a patient's unique 3-dimensional (3D) geometry without exposing the patient to radiation.

METHODS

Seven participants delivered normal saline containing a gadolinium-based contrast agent (GBCA) by either saline irrigation or nasal sprays on 1 side of the nasal cavity. The saline irrigation group included 2 participants (both healthy) while the nasal spray group included 5 participants (2 healthy, 2 post-FESS patients, 1 CRS patient without any sinus surgery). The distribution of new signal enhancement was assessed on each participant using magnetic resonance imaging (MRI). Serial scans were performed over an interval of 4 minutes in the nasal spray group to assess changes in intranasal distribution over time.

RESULTS

Signal enhancement was widespread within the nasal cavities and maxillary sinuses of participants (both healthy) that underwent sinus irrigation. For the nasal spray participants, the hotspots for signal enhancement were similar regardless of disease status or previous history of surgery. These included the internal nasal valve, anterior septum, inferior surface of the inferior turbinate, nasal floor, and nasopharynx. No signal enhancement was detected with nasal sprays in either unoperated or operated paranasal sinuses.

CONCLUSION

A technique has been developed using MRI evaluation of radioopaque contrast to characterize the temporospatial distribution of topical drug delivery within the sinonasal cavities.

Side asymmetry in nasal resistance correlate with nasal obstruction severity in patients with septal deformities: Computational fluid dynamics study

OBJECTIVES

The objective of this study was to investigate the relationship between side asymmetry in nasal resistance (NR) and severity of the nasal airway obstruction (NAO) in patients with different types of nasal septal deformity (NSD).

DESIGN

Computational fluid dynamics (CFD) study.

SETTING

The study was conducted in a tertiary medical centre.

PARTICIPANTS

The study included 232 patients, who were referred to the CT examination of the paranasal sinuses. Exclusion criteria were sinonasal and respiratory diseases that may interfere with the nasal obstruction. The presence and the type of NSD were recorded according to the Mladina's classification.

MAIN OUTCOME MEASURES

The presence and severity of NAO in each patient were assessed by NOSE questionnaire. Eight computational models of the nasal cavity were created from CT scans. Models represented seven Mladina's NSD types and a straight septum of a symptomless patient. CFD calculated airflow partitioning and NR for each nasal passage. Side differences in NR were calculated by the equation ∆NR = NR_left  - NR_right . The relationship between NOSE scores, airflow partitioning and side differences in NR was explored using Spearman's correlation analysis.

RESULTS

Mladina's types of NSD showed differences in airflow partitioning and the degree of side asymmetry in NR. A significant positive correlation was detected between side differences in NR and NOSE scores (R = .762, P = .028). A significant negative correlation was found between the per cent of unilateral airflow and NR (R = -.524, P = .037).

CONCLUSIONS

Our results demonstrated that side asymmetry in NR could explain differences in NAO severity related to the NSD type.

Efficiency evaluation of rapid maxillary expansion treatment on nasal septal deviation using tortuosity ratio from cone-beam computer tomography images

BACKGROUND AND OBJECTIVE

This study aims to assess the effect of Rapid Maxillary Expansion (RME) on Nasal Septal Deviation (NSD) changes from three-dimensional (3D) images.

METHODS

In this study, cone-beam computed tomography (CBCT) images from 15 patients with maxillary constriction (mean age 12 ± 1.6 years) were included. RME treatment with Hyrax appliance was performed in all patients. CBCT scans were taken at three different times; before appliance insertion (T0), after active expansion (T1) and 3 months after appliance insertion (T2). We developed a novel Matlab-based application to quantify NSD based on the tortuosity ratio by dividing the actual length of the septum by the ideal length in the mid-sagittal plane by using this application.

RESULTS

Tortuosity ratio (TR) values were found as 1.03 ± 0.03 (T0), 1.02 ± 0.02 (T1), and 1.02 ± 0.02 (T2). Differences of TR values among these groups were evaluated using the statistical method of ANOVA (ANalysis Of VAriance) for repeated measures with the significance level of p ≤ .05. Results showed significant reductions in TR values between T0-T1 (p ≤ .05) and between T0-T2 (p ≤ .05). Nonetheless, a significant difference between T1-T2 was not determined (p > .05).

CONCLUSIONS

As a result, we can conclude that the NSD degree is affected by the RME treatment. The developed application can be used for both educational and research purposes.

Impact of a Concha Bullosa on Nasal Airflow Characteristics in the Setting of Nasal Septal Deviation: A Computational Fluid Dynamics Analysis

BACKGROUND

A concha bullosa (CB) of the middle turbinate is frequently observed on the nondeviated side of patients with a nasal septal deviation (NSD). However, the impact of the CB on nasal airflow characteristics in patients with NSD has been incompletely defined.

OBJECTIVE

The purpose of this study was to evaluate the impact of a CB in patients with NSD on nasal airflow characteristics using a computational fluid dynamics (CFD) approach.

METHODS

Twenty patients with NSD and a unilateral CB of the middle turbinate on the nondeviated side (study group) were recruited. Another 20 patients with NSD without the formation of a CB (control group) were also enrolled. Using CFD, the maximal airflow velocity, nasal resistance, maximal wall shear stress, and minimal temperature in the bilateral nostrils of each group were assessed. Moreover, the volume of the nasal tract, surface area-to-volume ratio, and the total nasal resistance were compared between the study and control groups.

RESULTS

In the study group, no significant differences of airflow dynamics between the bilateral nasal cavities were observed. In the control group, however, there were statistically significant differences for maximal airflow velocity, nasal resistance, maximal wall shear stress, and minimal airflow temperature between the bilateral nostrils. The surface area-to-volume ratio and total nasal resistance in the study group was significantly higher and the nasal volume was significantly decreased than that in the control group.

CONCLUSION

CB of the middle turbinate on the nondeviated side of patients with NSD rendered airflow characteristics more evenly distributed between the bilateral nostrils as assessed by CFD. From an aerodynamics perspective, a CB may represent a compensatory action to normalize airflow dynamics. However, a CB may also result in constriction of the ipsilateral nasal cavity.

The effect of nasal shape on the thermal conditioning of inhaled air: Using clinical tomographic data to build a large-scale statistical shape model

In this paper, we investigate the heating function of the nasal cavity qualitatively, using a high-quality, large-scale statistical shape model. This model consists of a symmetrical and an asymmetrical part and provides a new and unique way of examining changes in nasal heating function resulting from natural variations in nasal shape (as obtained from 100 clinical CT scans). Data collected from patients suffering from different nasal or sinus-related complaints are included. Parameterized models allow us to investigate the effect of continuous deviations in shape from the mean nasal cavity. This approach also enables us to avoid many of the compounded effects on flow and heat exchange, which one would encounter when comparing different patient-specific models. The effects of global size, size-related features, and turbinate size are investigated using the symmetrical shape model. The asymmetrical model is used to investigate different types of septal deviation using Mladina's classification. The qualitative results are discussed and compared with findings from the existing literature.

Impact of Varying Types of Nasal Septal Deviation on Nasal Airflow Pattern and Warming Function: A Computational Fluid Dynamics Analysis

Nasal septal deviations (NSD) have been categorized into 7 types. The effect of these different deviations on airflow pattern and warming function has not been fully investigated. The purpose of this study was to utilize a computational fluid dynamics approach to assess the impact of NSD of varying types on nasal airflow and warming function. Patients with each type of NSD were enrolled in the study, and a normal participant as the control. Using a computational fluid dynamics approach, modeling of nasal function was performed. Indices of nasal function including airflow redistribution, total nasal resistance, airflow velocity, and airflow temperature were determined. Among all types of NSD, the maximal velocity and total nasal resistance were markedly higher in type 4 and 7 deviations. The flow partition and velocity distribution were also altered in type 4 and 7 as well as type 2 and 6 deviations. Airflow in all categories of NSD was fully warmed to a similar degree. From a computational aerodynamics perspective, the type of septal deviation may contribute to altered airflow characteristics. However, warming function was similar between septal deviation types. Future studies will help to ascertain the functional importance of septal deviation types and the applicability of these computational studies.

Virtual Surgery for the Nasal Airway: A Preliminary Report on Decision Support and Technology Acceptance

Importance

Nasal airway obstruction (NAO) is a common problem that affects patient quality of life. Surgical success for NAO correction is variable. Virtual surgery planning via computational fluid dynamics (CFD) has the potential to improve the success rates of NAO surgery.

Objective

To elicit surgeon feedback of a virtual surgery planning tool for NAO and to determine if this tool affects surgeon decision making.

Design, Setting, and Participants

For this cross-sectional study, 60-minute face-to-face interviews with board-certified otolaryngologists were conducted at a single academic otolaryngology department from September 16, 2016, through October 7, 2016. Virtual surgery methods were introduced, and surgeons were able to interact with the virtual surgery planning tool interface. Surgeons were provided with a patient case of NAO, and open feedback of the platform was obtained, with emphasis on surgical decision making.

Main Outcomes and Measures

Likert scale responses and qualitative feedback were collected for the virtual surgery planning tool and its influence on surgeon decision making.

Results

Our 9 study participants were all male, board-certified otolaryngologists with a mean (range) 15 (4-28) number of years in practice and a mean (range) number of nasal surgeries per month at 2.2 (0.0-6.0). When examined on a scale of 1 (not at all) to 5 (completely), surgeon mean (SD) score was 3.4 (0.5) for how realistic the virtual models were compared with actual surgery. On the same scale, when asked how much the virtual surgery planning tool changed surgeon decision making, mean (SD) score was 2.6 (1.6). On a scale of 1 (strongly disagree) to 7 (strongly agree), surgeon scores for perceived usefulness of the technology and attitude toward using it were 5.1 (1.1) and 5.7 (0.9), respectively.

Conclusions and Relevance

Our study shows positive surgeon experience with a virtual surgery planning tool for NAO based on CFD simulations. Surgeons felt that future applications and areas of study of the virtual surgery planning tool include its potential role for patient counseling, selecting appropriate surgical candidates, and identifying which anatomical structures should be targeted for surgical correction.

Level of Evidence

NA.

Comparison of Airflow Between Spreader Grafts and Butterfly Grafts Using Computational Flow Dynamics in a Cadaveric Model

Importance

Nasal valve compromise is a major cause of nasal obstruction, and multiple methods have been developed to address it.

Objective

To compare nasal airflow resistance, airflow partitioning, and mucosal cooling (heat flux) before and after 2 surgical interventions, butterfly and spreader graft placement, used to treat nasal valve compromise.

Design, Setting, and Participants

In this cadaveric tissue study, 4 fresh cadaveric heads underwent both spreader graft and butterfly graft surgical procedures in alternating sequence in March 2016. Preoperative and postoperative computed tomographic scans were used to generate 3-dimensional (3-D) models of the nasal airway. These models were then used in steady state computational fluid dynamics simulations of airflow and heat transfer during inspiration.

Intervention

Butterfly and spreader graft techniques.

Main Outcomes and Measures

Nasal airflow resistance, airflow partitioning, and heat flux.

Results

Donors 1, 2, and 3 were white males; donor 4, a white female. Computational fluid dynamics simulations during inspiration in 3-D models generated from preoperative and postoperative computed tomographic scans of the 4 cadaveric heads indicated reductions from preoperative values in nasal airflow resistance associated with both butterfly grafts (range, 20%-51%) and spreader grafts (range, 2%-29%). Butterfly grafts were associated with a greater reduction in nasal airflow resistance in models of all 4 cadaveric heads. Changes from preoperative values for heat flux, a biophysical variable that correlates with the subjective sensation of nasal patency, were more variable, ranging from -11% to 4% following butterfly grafts and -9% to 10% following spreader grafts. The preoperative airflow allocation in the left and right nostrils improved consistently with the butterfly graft. With the spreader graft, there were improvements for donors 1 and 4, but the allocations were worse for donors 2 and 3.

Conclusions and Relevance

The results of this study suggest that the more recently developed butterfly graft technique may be associated with a similar level of improved nasal airflow as that observed with the use of a spreader graft in nasal valve compromise. Both interventions were associated with comparable changes in heat flux. Because this study addressed only static internal nasal valve stenosis, even greater differences in air flow and heat flux between the 2 techniques may be anticipated in a dynamic model. Further investigation in patients is warranted.

Level of Evidence

NA.

Thermal water delivery in the nose: experimental results describing droplet deposition through computational fluid dynamics

Thermal water therapies have a role in treating various inflammatory disorders dating back to ancient Greece. Several studies have demonstrated beneficial effects of thermal water inhalations for upper respiratory disorders, such as improvement of mucociliary function and reduction of inflammatory cell infiltration. This experimental study describes the numerical investigation and clinical implications of thermal water droplet deposition in the nasal cavity of a single patient. To our knowledge, the numerical flow simulations described are the first investigations specifically designed for thermal water applications. To simulate nasal airflow, a patient-specific 3D computer model was created from a CT scan. The numerical approach is based on the Large Eddy Simulation (LES) technique and builds entirely upon open-source software. Deposition on mucosa was studied for two droplet sizes (5 and 10 μm diameter), corresponding to common thermal therapy applications (aerosol and vapour inhalation). The simulations consider steady inspiration at two different (low and moderate) breathing intensities. The results of this preliminary study show specific deposition patterns that favour droplet deposition in the middle meatus region to the inferior meatus, with particle size- and breathing intensity-related effects. These global data on particle deposition differ from findings related to the single-phase nasal airflow, which is more evenly distributed between the middle and inferior meatus. The potential clinical consequences of deposition data are discussed. The study furthermore provides evidence for the effectiveness of thermal aerosol and vapour inhalation therapies in reaching important areas of nasal mucosa with considerable clinical significance.

A hierarchical stepwise approach to evaluate nasal patency after virtual surgery for nasal airway obstruction

BACKGROUND

Despite advances in medicine and expenditures associated in treatment of nasal airway obstruction, 25-50% of patients undergoing nasal surgeries complain of persistent obstructive symptoms. Our objective is to develop a "stepwise virtual surgery" method that optimizes surgical outcomes for treatment of nasal airway obstruction.

METHODS

Pre-surgery radiographic images of two subjects with nasal airway obstruction were imported into Mimics imaging software package for three-dimension reconstruction of the airway. A hierarchical stepwise approach was used to create seven virtual surgery nasal models comprising individual (inferior turbinectomy or septoplasty) procedures and combined inferior turbinectomy and septoplasty procedures via digital modifications of each subject's pre-surgery nasal model. To evaluate the effects of these procedures on nasal patency, computational fluid dynamics modeling was used to perform steady-state laminar inspiratory airflow and heat transfer simulations in every model, at resting breathing. Airflow-related variables were calculated for virtual surgery models and compared with dataset containing results of healthy subjects with no symptoms of nasal obstruction.

FINDINGS

For Subject 1, nasal models with virtual septoplasty only and virtual septoplasty plus inferior turbinectomy on less obstructed side were within the healthy reference thresholds on both sides of the nasal cavity and across all three computed variables. For Subject 2, virtual septoplasty plus inferior turbinectomy on less obstructed side model produced the best result.

INTERPRETATION

The hierarchical stepwise approach implemented in this preliminary report demonstrates computational fluid dynamics modeling ability to evaluate the efficiency of different surgical procedures for nasal obstruction in restoring nasal patency to normative level.

Convoluted nasal passages function as efficient heat exchangers in ankylosaurs (Dinosauria: Ornithischia: Thyreophora)

Convoluted nasal passages are an enigmatic hallmark of Ankylosauria. Previous research suggested that these convoluted nasal passages functioned as heat exchangers analogous to the respiratory turbinates of mammals and birds. We tested this hypothesis by performing a computational fluid dynamic analysis on the nasal passages of two ankylosaurs: Panoplosaurus mirus and Euoplocephalus tutus. Our models predicted that Panoplosaurus and Euoplocephalus would have required 833 and 1568 thermal calories, respectively, to warm a single breath of air by 20°C. Heat recovery during exhalation resulted in energy savings of 65% for Panoplosaurus and 84% for Euoplocephalus. Our results fell well within the range of values for heat and water savings observed in extant terrestrial amniotes. We further tested alternate airway reconstructions that removed nasal passage convolutions or reduced nasal vestibule length. Our results revealed that the extensive elaboration observed in the nasal vestibules of ankylosaurs was a viable alternative to respiratory turbinates with regards to air conditioning. Of the two dinosaurs tested, Euoplocephalus repeatedly exhibited a more efficient nasal passage than Panoplosaurus. We suggest that the higher heat loads associated with the larger body mass of Euoplocephalus necessitated these more efficient nasal passages. Our findings further indicate that the evolution of complicated airways in dinosaurs may have been driven by the thermal requirements of maintaining cerebral thermal homeostasis.

Nasal surgery handled by CFD tools

Annually, hundreds of thousands of surgical interventions to correct nasal airway obstruction are performed throughout the world. Recent studies have noted that a significant number of patients have persistent symptoms of nasal obstruction postoperatively. In the present work, we introduce a new methodology that raises the success rate of nasal cavity surgery. In this procedure, the surgeon performs virtual surgery on a 3D nasal model of a patient prior to the real surgery. The main goal of the methodology is to guide the surgeon throughout the virtual operation using mathematical estimators based on CFD results. The virtual surgery intervention ends as soon as the estimators fall into a region of a Cartesian coordinate system with a high success probability. This region is defined according to a statistical analysis of estimators corresponding to sets of healthy and diseased cavities. As examples of this application, this study includes 2 surgical operations performed with this innovative methodology on patients with severe nasal obstruction. The patients underwent nasal surgery according to the final nasal geometry revealed by CFD-guided virtual surgery. Currently, both subjects show high degrees of satisfaction.

Examining mesh independence for flow dynamics in the human nasal cavity

Increased computational resources provide new opportunities to explore sophisticated respiratory modelling. A survey of recent publications showed a steady increase in the number of mesh elements used in computational models over time. Complex geometries such as the nasal cavity exhibit sharp gradients and irregular curvatures, leading to abnormal flow development across their surfaces. As such, a robust method for examining the near-wall mesh resolution is required. The non-dimensional wall unit y⁺ (often used in turbulent flows) was used as a parameter to evaluate the near-wall mesh in laminar flows. Mesh independence analysis from line profiles showed that the line location had a significant influence on the result. Furthermore, using a single line profile as a measure for mesh convergence was unsuitable for representing the entire flow field. To improve this, a two-dimensional (2D) cross-sectional plane subtraction method where scalar values (such as the velocity magnitude) on a cross-sectional plane were interpolated onto a regularly spaced grid was proposed. The new interpolated grid values from any two meshed models could then be compared for changes caused by the different meshed models. The application of this method to three-dimensional (3D) volume subtraction was also demonstrated. The results showed that if the near-wall mesh was sufficiently refined, then narrow passages were less reliant on the overall mesh size. However, in wider passages, velocity magnitudes were sensitive to mesh size, requiring a more refined mesh.

The Impact of Septal Deviation on Intranasal Schirmer Test Values

Objective

Intranasal Schirmer test serves as an objective measurement for evaluation of nasal secretion and humidity. This study aimed to evaluate the effect of septal deviation on nasal secretion and humidity by measuring the intranasal Schirmer test values in patients who had septal deviation and compare it to the values of our healthy volunteers.

Methods

The study included 52 patients with nasal septum deviation and 52 volunteers without any rhinologic complaints or deviated nasal septum. Intranasal Schirmer test was performed to all patients and volunteers for both nasal cavities.

Results

The intranasal Schirmer test values of the convex (deviated) side were lower than that of the concave (non-deviated) side (20.71 and 23.35 respectively); although this difference was not statistically significant (p=0.054,). After excluding the four patients with equal Schirmer test results on both sides, 70% (34/48) of our patients had lower intranasal Schirmer test values on the deviated side. There was no statistically significant difference between the Schirmer test values of the patients with septal deviation and the volunteers without septal deviation (p>0.05).

Conclusion

The Schirmer test values of the deviated sides were less than the values of the contralateral side in majority of our patients. This finding supports the negative effect of nasal septum deviation on nasal humidification, although the difference did not reach statistical significance.

Numerical simulation of thermal water delivery in the human nasal cavity

This work describes an extensive numerical investigation of thermal water delivery for the treatment of inflammatory disorders in the human nasal cavity. The numerical simulation of the multiphase air-droplets flow is based upon the Large Eddy Simulation (LES) technique, with droplets of thermal water described via a Lagrangian approach. Droplet deposition is studied for different sizes of water droplets, corresponding to two different thermal treatments, i.e. aerosol and inhalation. Numerical simulations are conducted on a patient-specific anatomy, employing two different grid sizes, under steady inspiration at two breathing intensities. The results are compared with published in vivo and in vitro data. The effectiveness of the various thermal treatments is then assessed qualitatively and quantitatively, by a detailed analysis of the deposition patterns of the droplets. Discretization effects on the deposition dynamics are addressed. The level of detail of the present work, together with the accuracy afforded by the LES approach, leads to an improved understanding of how the mixture of air-water droplets is distributed within the nose and the paranasal sinuses.

Recommendations for Simulating Microparticle Deposition at Conditions Similar to the Upper Airways with Two-Equation Turbulence Models

The development of a CFD model, from initial geometry to experimentally validated result with engineering insight, can be a time-consuming process that often requires several iterations of meshing and solver set-up. Applying a set of guidelines in the early stages can help to streamline the process and improve consistency between different models. The objective of this study was to determine both mesh and CFD solution parameters that enable the accurate simulation of microparticle deposition under flow conditions consistent with the upper respiratory airways including turbulent flow. A 90° bend geometry was used as a characteristic model that occurs throughout the airways and for which high-quality experimental aerosol deposition data is available in the transitional and turbulent flow regimes. Four meshes with varying degrees of near-wall resolution were compared, and key solver settings were applied to determine the parameters that minimize sensitivity to the near-wall (NW) mesh. The Low Reynolds number (LRN) k-ω model was used to resolve the turbulence field, which is a numerically efficient two-equation turbulence model, but has recently been considered overly simplistic. Some recent studies have used more complex turbulence models, such as Large Eddy Simulation (LES), to overcome the perceived weaknesses of two-equation models. Therefore, the secondary objective was to determine whether the more computationally efficient LRN k-ω model was capable of providing deposition results that were comparable to LES. Results show how NW mesh sensitivity is reduced through application of the Green-Gauss Node-based gradient discretization scheme and physically realistic near-wall corrections. Using the newly recommended meshing parameters and solution guidelines gives an excellent match to experimental data. Furthermore, deposition data from the LRN k-ω model compares favorably with LES results for the same characteristic geometry. In summary, this study provides a set of meshing and solution guidelines for simulating aerosol deposition in transitional and turbulent flows found in the upper respiratory airways using the numerically efficient LRN k-ω approach.

Effects of nasal septum perforation repair on nasal airflow: An analysis using computational fluid dynamics on preoperative and postoperative three-dimensional models

OBJECTIVE

The purpose of this research is to examine the changes in nasal airflow dynamics before and after the nasal perforation repair.

METHODS

Three dimensional (3D) models of the nasal cavity before and after septal perforation repair was reconstructed using preoperative and postoperative computed tomography (CT) images of a patient. The numerical simulation was carried out using ANSYS CFX V15.0. Pre- and post-operative models were compared by their velocity, pressure (P), pressure gradient (PG), wall shear (WS), shear strain rate (SSR) and turbulence kinetic energy (TKE) in three plains.

RESULTS

In the post-operative state, the cross flows disappeared. In preoperative state, there were areas showing high PG, WS, SSR at the posterior border of the perforation, which exactly correspond to the area showing erosive mucosa on endoscopic inspection of the patient. In postoperative state, such high PG, WS and SSR areas disappeared. High TKEs also disappeared after surgery.

CONCLUSION

The effects of septal perforation repair on airflow dynamics were evaluated using computer fluid dynamics (CFD). High WS, PG and SSR observed at the edge of the septal perforation may be related to the clinical symptom such as nasal bleeding and pain. TKE was considered to cause nasal symptom.

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

BACKGROUND

Computational fluid dynamic (CFD) simulations have greatly improved the understanding of nasal physiology. We postulate that simulating the entire and repeated respiratory nasal cycles, within the whole sinonasal cavities, is mandatory to gather more accurate observations and better understand airflow patterns.

METHODS

A 3-dimensional (3D) sinonasal model was constructed from a healthy adult computed tomography (CT) scan which discretized in 6.6 million cells (mean volume, 0.008 mm³ ). CFD simulations were performed with ANSYS©FluentTMv16.0.0 software with transient and turbulent airflow (k-ω model). Two respiratory cycles (8 seconds) were simulated to assess pressure, velocity, wall shear stress, and particle residence time.

RESULTS

The pressure gradients within the sinus cavities varied according to their place of connection to the main passage. Alternations in pressure gradients induced a slight pumping phenomenon close to the ostia but no movement of air was observed within the sinus cavities. Strong movements were observed within the inferior meatus during expiration contrary to the inspiration, as in the olfactory cleft at the same time. Particle residence time was longer during expiration than inspiration due to nasal valve resistance, as if the expiratory phase was preparing the next inspiratory phase. Throughout expiration, some particles remained in contact with the lower turbinates. The posterior part of the olfactory cleft was gradually filled with particles that did not leave the nose at the next respiratory cycle. This pattern increased as the respiratory cycle was repeated.

CONCLUSION

CFD is more efficient and reliable when the entire respiratory cycle is simulated and repeated to avoid losing information.

Robust nondimensional estimators to assess the nasal airflow in health and disease

There are significant variations of both human nose shapes and airflow patterns inside nasal cavities, so it is difficult to provide a comprehensive medical identification using a universal template for what otolaryngologists consider normal breathing at rest. In addition, airflow patterns present even more random characteristics in diseased nasal cavities. To give a medical assessment to differentiate the nasal cavities in health and disease, we propose 2 nondimensional estimators obtained from both medical images and computational fluid dynamics. The first mathematical estimator ϕ is a function of geometric features and potential asymmetries between nasal passages, while the second estimator R represents in fluid mechanics terms the total nasal resistance that corresponds to the atmosphere-choana pressure drop. These estimators only require global information such as nasal geometry and magnitudes of flow determined by simulations under laminar conditions. We find that these estimators take low and high values for healthy and diseased nasal cavities, respectively. Our study, based on 24 healthy and 25 diseased Caucasian subjects, reveals that there is an interval of values associated with healthy cavities that clusters in a small region of the plane ϕ-R. Therefore, these estimators can be seen as a first approximation to provide nasal airflow data to the clinician in a noninvasive method, as the computed tomography scan that provides the required images is routinely obtained as a result of the preexisting naso-sinusal condition.

New CFD tools to evaluate nasal airflow

Computational fluid dynamics (CFD) is a mathematical tool to analyse airflow. As currently CFD is not a usual tool for rhinologists, a group of engineers in collaboration with experts in Rhinology have developed a very intuitive CFD software. The program MECOMLAND^® only required snapshots from the patient's cross-sectional (tomographic) images, being the output those results originated by CFD, such as airflow distributions, velocity profiles, pressure, temperature, or wall shear stress. This is useful complementary information to cover diagnosis, prognosis, or follow-up of nasal pathologies based on quantitative magnitudes linked to airflow. In addition, the user-friendly environment NOSELAND^® helps the medical assessment significantly in the post-processing phase with dynamic reports using a 3D endoscopic view. Specialists in Rhinology have been asked for a more intuitive, simple, powerful CFD software to offer more quality and precision in their work to evaluate the nasal airflow. We present MECOMLAND^® and NOSELAND^® which have all the expected characteristics to fulfil this demand and offer a proper assessment with the maximum of quality plus safety for the patient. These programs represent a non-invasive, low-cost (as the CT scan is already performed in every patient) alternative for the functional study of the difficult rhinologic case. To validate the software, we studied two groups of patients from the Ear Nose Throat clinic, a first group with normal noses and a second group presenting septal deviations. Wall shear stresses are lower in the cases of normal noses in comparison with those for septal deviation. Besides, velocity field distributions, pressure drop between nasopharynx and the ambient, and flow rates in each nostril were different among the nasal cavities in the two groups. These software modules open up a promising future to simulate the nasal airflow behaviour in virtual surgery intervention scenarios under different pressure or temperature conditions to understand the effects on nasal airflow.

Advances in Technology for Functional Rhinoplasty: The Next Frontier

Advances in computer modeling and simulation technologies have the potential to provide facial plastic surgeons with information and tools that can aid in patient-specific surgical planning for rhinoplasty. Finite element modeling and computational fluid dynamics are modeling technologies that have been applied to the nose to study structural biomechanics and nasal airflow. Combining these technologies with patient-specific imaging data and symptom measures has the potential to alter the future landscape of nasal surgery.

Use of CT to evaluate and compare intranasal features in brachycephalic and normocephalic dogs

OBJECTIVES

To evaluate and compare nasal mucosal contact, septal deviation and caudal aberrant nasal turbinates in brachycephalic and normocephalic dogs using computed tomography.

METHODS

Dogs without nasal disease and having undergone computed tomography scan of the head (plica alaris to the cribiform plate) were retrospectively selected and divided into brachycephalic and normocephalic groups. Eighteen brachycephalic and 32 normocephalic dogs were included. Anatomic criteria were used to locate predetermined pairs of intranasal structures and nasal mucosal contact was described as present or absent for each site. Septal deviations were identified and measured using angle of septal deviation. Caudal aberrant nasal turbinates were identified and categorised when present.

RESULTS

Prevalence of nasal mucosal contact was significantly higher in brachycephalic dogs. No significant difference was seen in prevalence or in angle of septal deviation between groups. Prevalence of caudal aberrant nasal turbinates was significantly higher in brachycephalic dogs.

CLINICAL SIGNIFICANCE

Nasal mucosal contact and caudal aberrant nasal turbinates were significantly more prevalent in brachycephalic dogs than in normocephalic dogs in our study. Computed tomography can be a valuable aid in obtaining data on nasal mucosal contact, caudal aberrant nasal turbinates and septal deviations. Combination of computed tomography with endoscopy and functional airway testing would be useful to further evaluate the correlation between intranasal features and symptoms of brachycephalic airway syndrome.

Impact of Middle versus Inferior Total Turbinectomy on Nasal Aerodynamics

OBJECTIVES

This computational study aims to (1) use virtual surgery to theoretically investigate the maximum possible change in nasal aerodynamics after turbinate surgery, (2) quantify the relative contributions of the middle and inferior turbinates to nasal resistance and air conditioning, and (3) quantify to what extent total turbinectomy impairs the nasal air-conditioning capacity.

STUDY DESIGN

Virtual surgery and computational fluid dynamics.

SETTING

Academic tertiary medical center.

SUBJECTS AND METHODS

Ten patients with inferior turbinate hypertrophy were studied. Three-dimensional models of their nasal anatomies were built according to presurgery computed tomography scans. Virtual surgery was applied to create models representing either total inferior turbinectomy (TIT) or total middle turbinectomy (TMT). Airflow, heat transfer, and humidity transport were simulated at a steady-state inhalation rate of 15 L/min. The surface area stimulated by mucosal cooling was defined as the area where heat fluxes exceed 50 W/m(2).

RESULTS

In both virtual total turbinectomy models, nasal resistance decreased and airflow increased. However, the surface area where heat fluxes exceed 50 W/m(2) either decreased (TIT) or did not change significantly (TMT), suggesting that total turbinectomy may reduce the stimulation of cold receptors by inspired air. Nasal heating and humidification efficiencies decreased significantly after both TIT and TMT. All changes were greater in the TIT models than in the TMT models.

CONCLUSION

TIT yields greater increases in nasal airflow but also impairs the nasal air-conditioning capacity to a greater extent than TMT. Radical resection of the turbinates may decrease the surface area stimulated by mucosal cooling.

Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo

We are flat-faced hominins with an external nose that protrudes from the face. This feature was derived in the genus Homo, along with facial flattening and reorientation to form a high nasal cavity. The nasal passage conditions the inhaled air in terms of temperature and humidity to match the conditions required in the lung, and its anatomical variation is believed to be evolutionarily sensitive to the ambient atmospheric conditions of a given habitat. In this study, we used computational fluid dynamics (CFD) with three-dimensional topology models of the nasal passage under the same simulation conditions, to investigate air-conditioning performance in humans, chimpanzees, and macaques. The CFD simulation showed a horizontal straight flow of inhaled air in chimpanzees and macaques, contrasting with the upward and curved flow in humans. The inhaled air is conditioned poorly in humans compared with nonhuman primates. Virtual modifications to the human external nose topology, in which the nasal vestibule and valve are modified to resemble those of chimpanzees, change the airflow to be horizontal, but have little influence on the air-conditioning performance in humans. These findings suggest that morphological variation of the nasal passage topology was only weakly sensitive to the ambient atmosphere conditions; rather, the high nasal cavity in humans was formed simply by evolutionary facial reorganization in the divergence of Homo from the other hominin lineages, impairing the air-conditioning performance. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in the flat-faced Homo. Thus, the air-conditioning faculty in the nasal passages was probably impaired in early Homo members, although they have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved “Out of Africa” to explore the more severe climates of Eurasia.

This is the first investigation of nasal air conditioning in nonhuman hominoids based on computational fluid dynamics with digital topological models of the nasal passage made using medical imaging. Our comparative results of humans, chimpanzees, and macaques show that the inhaled air is conditioned poorly in humans compared with nonhuman primates. We also show that our protruding external nose has little effect on improving air conditioning. The nasal anatomy in Homo was weakly sensitive to the ambient atmosphere conditions in evolution, but was formed passively by facial reorganization in this genus. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in flat-faced Homo. Thus, despite an impaired air-conditioning conformation in the nasal passages, Homo members must have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved “Out of Africa” in the Early Pleistocene to explore the more severe climates and ecological environments of Eurasia.