Numerical simulation of the effects of inferior turbinate surgery on nasal airway heating capacity

In-silico decongested trial effects on the impaired breathing function of a bulldog suffering from severe brachycephalic obstructive airway syndrome

BACKGROUND AND OBJECTIVE

Brachycephalic obstructive airway syndrome (BOAS) susceptible dogs (e.g., French bulldog), suffer health complications related to deficient breathing primarily due to anatomical airway geometry. Surgical interventions are known to provide acceptable functional and cosmetic results; however, the long-term post-surgery outcome is not well known. In silico analysis provides an objective measure to quantify the respiratory function in postoperative dogs which is critical for successful long-term outcomes. A virtual surgery to open the airway can explore the ability for improved breathing in an obstructed airway of a patient dog, thus supporting surgeons in pre-surgery planning using computational fluid dynamics.

METHODS

In this study five surgical interventions were generated with a gradual increment of decongested levels in a bulldog based on computed tomography images. The effects of the decongested airways on the breathing function of a patient bulldog, i.e., airflow characteristics, pressure drop, wall shear stress, and air-conditioning capacity, were quantified by benchmarking against a clinically healthy bulldog using computational fluid dynamics (CFD) method.

RESULTS

Our findings demonstrated a promising decrease in excessive airstream velocity, pressure drop, and wall shear stress in virtual surgical scenarios, while constantly preserving adequate air-conditioning efficiency. A linear fit curve was proposed to correlate the reduction in the pressure drop and decongested level.

CONCLUSIONS

The in silico analysis is a viable tool providing visual and quantitative insight into new unexplored surgical techniques.

New insights into the variability of upper airway morphology in modern humans

The biological adaptation of the human lineage to its environment is a recurring question in paleoanthropology. Particularly, how eco-geographic factors (e.g., environmental temperature and humidity) have shaped upper airway morphology in hominins have been subject to continuing debate. Nasal shape is the result of many intertwined factors that include, but are not limited to, genetic drift, sexual selection, or adaptation to climate. A quantification of nasal airway (NA) morphological variation in modern human populations is crucial to better understand these multiple factors. In the present research, we study 195 in vivo CT scans of adult individuals collected in five different geographic areas (Chile, France, Cambodia, Russia, and South Africa). After segmentation of the nasal airway, we reconstruct 3D meshes that are analyzed with a landmark-free geometric morphometrics method based on surface deformation. Our results highlight subtle but statistically significant morphological differences between our five samples. The two morphologically closest groups are France and Russia, whose NAs are longer and narrower, with an important protrusion of the supero-anterior part. The Cambodian sample is the most morphologically distinct and clustered sample, with a mean NA that is wider and shorter. On the contrary, the Chilean sample form the most scattered cluster with the greatest intra-population variation. The South African sample is morphologically close to the Cambodian sample, but also partially overlaps the French and Russian variation. Interestingly, we record no correlation between NA volume and geographic groups, which raises the question of climate-related metabolic demands for oxygen consumption. The other factors of variation (sex and age) have no influence on the NA shape in our samples. However, NA volume varies significantly according both to sex and age: it is higher in males than in females and tends to increase with age. In contrast, we observe no effect of temperature or humidity on NA volume. Finally, we highlight the important influence of asymmetries related to nasal septum deviations in NA shape variation.

Detailed Assessment of Nasal Inter-Chamber Anatomical Variations and Its Effect on Flow Apportionment and Inhalation Exposure Patterns

Although many parametric studies have been conducted in developing standardized nasal geometry and analysing associated airflow dynamics, most of them are based on symmetrical nasal chambers assumption, while the inter-chamber variations due to the morphological asymmetry of the two nasal chambers are much less investigated. To address this issue, this paper presents an inter-chamber anatomical variability study by developing a shape comparison method to quantify inter-chamber anatomical differences. Then the anatomical deviation is correlated with the flow apportionment and the associated nanoparticle deposition patterns using CFD method. Results show that noticeable inter-chamber difference is observed especially in the inferior and middle passages where most inhaled flow is distributed to. Additionally, the shape of vestibule notch and septum deviation contributes to the discrepancy flow behaviour between two chambers. Consequently, these differences lead to variations in regional nanoparticle deposition, especially for 1 nm particles in the olfactory region, where the inter-chamber differences can reach up to 400%. Our results suggest that the inter-chamber anatomical variation should be considered when developing standardized nasal models.

Analysis of inferior nasal turbinate width and concha bullosa in subjects with nasal septum deviation: a cone beam tomography study

Background

In individuals with nasal septal deviation (NSD), compensatory hypertrophy of the nasal turbinates occurs as a protective mechanism of the nasal passage from dry and cold air. NSD associated nasal turbinate hypertrophy is usually recurrent, requiring repetitive imaging. Therefore, a multiplanar imaging modality with a low radiation dose is best suited for long-term follow-up of this condition. This study aimed to evaluate the association of width of inferior turbinates and presence of concha bullosa with the degree of NSD using Cone beam computed tomography (CT).

Methods

The CBCT scans of 100 patients with NSD were selected as per convenience sampling and were evaluated by two maxillofacial radiologists. The width of the non-hypertrophied inferior turbinate (NHT) on the convex side of the NSD, and hypertrophic inferior turbinates (HT) on the concave side of the NSD were measured at three locations. The septal deviation angle (SDA) and the presence of concha bullosa (CB) were determined.

Results

A significant difference was observed in the anterior, middle, posterior, and mean widths between HT and NHT (p < 0.001). There was a significant difference in the widths of the HT and NHT among different types of NSD. A strong positive correlation (r = 0.71, p < 0.001) was found between SDA and the mean width of the HT. Age (P = 0.71) and gender (P = 0.65) had no significant difference among different types of NSD. Regression analysis revealed that the presence of CB (p = 0.01) and middle width of the HT (p < 0.001) are significant predictors of SDA and type of NSD.

Conclusion

The results of the present study reveal that the middle width of the HT and the presence of CB influence the degree of NSD. The present study results recommend the use of CBCT as a substitutive low radiation dose imaging modality for evaluation of NSD, CB, and associated inferior turbinate hypertrophy.

Computational technology for nasal cartilage-related clinical research and application

Surgeons need to understand the effects of the nasal cartilage on facial morphology, the function of both soft tissues and hard tissues and nasal function when performing nasal surgery. In nasal cartilage-related surgery, the main goals for clinical research should include clarification of surgical goals, rationalization of surgical methods, precision and personalization of surgical design and preparation and improved convenience of doctor-patient communication. Computational technology has become an effective way to achieve these goals. Advances in three-dimensional (3D) imaging technology will promote nasal cartilage-related applications, including research on computational modelling technology, computational simulation technology, virtual surgery planning and 3D printing technology. These technologies are destined to revolutionize nasal surgery further. In this review, we summarize the advantages, latest findings and application progress of various computational technologies used in clinical nasal cartilage-related work and research. The application prospects of each technique are also discussed.

Partial Preservation of the Inferior Turbinate in Endoscopic Medial Maxillectomy: A Computational Fluid Dynamics Study

Background

Endoscopic medial maxillectomy (EMM) is a workhorse for multiple sinonasal conditions. To reduce its burden on the sinonasal physiology, several modified EMM (M-EMM) have been proposed. Objective: In order to provide a theoretical basis for EMM and its modifications, this study introduces a computational fluid dynamics (CFD) model, based on a time-resolved direct numerical simulation, describing EMM and assessing the role of the M-EMM in preserving the overall fluid dynamics of the sinonasal cavities.

Methods

A normal sinonasal CT scan was converted into a geometrical model and used as a reference; 2 anatomies were then created by virtual surgery, mimicking EMM and M-EMM, with the latter sparing the anterior portion of inferior turbinate and medial maxillary sinus wall. The airflow was simulated in the models via the OpenFOAM CFD software and compared in terms of flow rate, mean and fluctuating velocity, vorticity, and turbulent structures.

Results

The analysis shows that EMM induces a massive flow rate increase in the operated side, which becomes less obvious in the M-EMM model. In contrast to M-EMM, EMM induces higher velocity fields that reach the maxillary sinus. Velocity and vorticity fluctuations are negligible in the baseline model, but become increasingly evident and widespread in the M-EMM and EMM models.

Conclusions

A significant disruption of the nasal fluid dynamics is observed in EMM, while M-EMM minimizes variations and reduces interference with nasal air conditioning. Our analysis provides insights into the pathophysiology of radical sinus surgery and provides a theoretical basis for the ability of M-EMM to reduce the temporary surgery-related changes on both healthy and operated sides.

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.

In silico approaches to respiratory nasal flows: A review

The engineering discipline of in silico fluid dynamics delivers quantitative information on airflow behaviour in the nasal regions with unprecedented detail, often beyond the reach of traditional experiments. The ability to provide visualisation and analysis of flow properties such as velocity and pressure fields, as well as wall shear stress, dynamically during the respiratory cycle may give significant insight to clinicians. Yet, there remains ongoing challenges to advance the state-of-the-art further, including for example the lack of comprehensive CFD modelling on varied cohorts of patients. The present article embodies a review of previous and current in silico approaches to simulating nasal airflows. The review discusses specific modelling techniques required to accommodate physiologically- and clinically-relevant findings. It also provides a critical summary of the reported results in the literature followed by an outlook on the challenges and topics anticipated to drive research into the future.

Review: The role of computational simulation in understanding the postoperative sinonasal environment

Nasal surgery improves symptoms in a majority of patients for whom medical treatment has failed. In rhinosinusitis patients, endoscopic sinus surgery aims to alleviate obstruction and re-establish mucociliary clearance. Surgery alters the structure-function relationship within the nasal passage, which is difficult to assess clinically. Computational modelling has been used to investigate this relationship by simulating air flow and environmental variables inside realistic three-dimensional models of the human nasal airway but many questions remain unanswered and need further investigation. The application of computational models to improve pre-surgical planning and post-surgical treatment may not be currently possible due to the absence of knowledge correlating the model-predicted parameters to physiological variables. Links between these parameters to patient outcomes are yet to be established. This article reviews the recent application of computational modelling to understand the nasal structure-function relationship following surgery in patients with sinusitis and nasal obstruction.

Lin E, Poetker DM, Garcia GJM. Clinical Importance of Nasal Air Conditioning: A Review of the Literature

Background

Nasal air conditioning (ie, heating and humidification of inspired air) is an important function of the nasal cavity. This function may be reduced in cases of aggressive nasal surgery. Future virtual surgery planning tools may be used to design surgical approaches that preserve the nasal air conditioning capacity while decreasing airflow resistance. However, it is unclear whether there is a threshold below which impaired nasal air conditioning is associated with negative health consequences.

Objective

This study aims to review the literature on the clinical impact of reduced nasal air conditioning and its implications for nasal surgery outcomes.

Methods

A literature search was performed on PubMed and Scopus databases for articles that investigated the effect of air temperature and humidity on mucociliary clearance, respiratory epithelial structure, and the prevalence and severity of respiratory diseases.

Results

Inspiration of cold, dry air has direct effects on the respiratory epithelium, such as reduced mucociliary clearance and loss of cilia. Nasal surgeries do inflict some changes to the nasal mucosa and geometry that may result in decreased heating and humidification, but it is unclear how long these effects last. Laryngectomy patients serve as a human model for the absence of nasal air conditioning. The heat and moisture exchangers that many laryngectomy patients wear have been shown to improve lung function and reduce pulmonary symptoms associated with breathing unconditioned air, such as increased coughing and thickened mucus.

Conclusion

Nasal air conditioning is an important mechanism to maintain mucociliary clearance and prevent infection by inhaled pathogens. Preservation of nasal air conditioning capacity should be considered in the implementation of future virtual surgery planning tools. However, a threshold for the onset of negative health consequences due to impaired nasal air conditioning is not yet available.

Functional relevance of computational fluid dynamics in the field of nasal obstruction: A literature review

BACKGROUND

Nasal airway obstruction (nasal obstruction) is a common symptom affecting the quality of life of patients. It can be estimated by patient perception or physical measurements. Computational fluid dynamics (CFD) can be used to analyse nasal ventilation modalities. There is a lack of comparative studies investigating the correlations between CFD variables and patient perception or physical measurements.

OBJECTIVE OF THE REVIEW

Our goal was to define correlations between CFD variables and patient perception and physical measurements. We also aimed to identify the most reliable CFD variable (heat flux, WSS, total pressure, temperature…) characterising nasal breathing perception.

TYPE OF REVIEW

Systematic literature review using PRISMA guidelines.

SEARCH STRATEGY

The selected studies were obtained from the US National Library of Medicine (PubMed) online database, MEDLINE (Ovid), Google Scholar and the Cochrane Library using a combination of MeSH terms (nose, paranasal sinus, fluid dynamics, rhinology) and non-MeSH terms (CFD, nasal airway, nasal airflow, numerical, nasal symptoms). Studies that did not incorporate objective or subjective clinical assessment were excluded.

EVALUATION METHOD

We compared all results obtained by authors regarding CFD variables and assessment of nasal airway obstruction (clinical or physical).

RESULTS

To compare nasal obstruction with CFD variables, most authors use CFD-calculated nasal resistances, airflow, heat flux, wall shear stress, total pressure, velocities and streamlines. We found that heat flux appears to be the CFD variable most closely correlated with patient perception. Total pressure, wall shear stress and velocities are also useful and show good correlations. Correlations between CFD-calculated nasal resistances and patient perception are stronger after correction of the nasal cycle.

CONCLUSIONS

The growing number of CFD studies on the nose has led to a better understanding of nasal obstruction. The clinical interpretation of previously unknown data, such as WSS and heat flux, is opening up new horizons in the understanding of this symptom. Heat fluxes are among the best CFD values correlated with patient perception. More studies need to be performed including temperature and humidity exchanges.

[Negative effects of stripe conchotomy on intranasal conditioning]

OBJECTIVE

Partial resection of the caudal part of the inferior turbinate including the head is still performed in rhinosurgery ("stripe conchotomy"). However, extensive resections of the turbinate affect nasal airflow and intranasal conditioning. The aim of this study was to determine the effect of partial resection of the inferior turbinate including its head on intranasal air flow as well as warming and humidification of the inspired air by means of computational fluid dynamics.

MATERIALS AND METHODS

A bilateral, realistic nasal model was created based on the CT scan of a patient. A unilateral partial resection of the lower turbinate on the right side had been performed externally. A numerical simulation was performed to analyze intranasal air flow patterns, temperature, and humidity distribution of the inspired air.

RESULTS

Due to the partial resection of the lower turbinate on the right side, the flow pattern was significantly altered compared to the opposite side. Resection leads to a centered and higher velocity in the inferior nasal meatus as well as to reduced heating and humidification of the inhaled air compared to the untouched left nasal cavity.

CONCLUSION

Partial resection of the caudal part of the inferior turbinate may lead to disturbed intranasal conditioning of inspired air if performed too radically. Therefore, if possible, this procedure should be avoided and a more gentle mucosal procedure chosen.

Review: The role of computational simulation in understanding the postoperative sinonasal environment

Nasal surgery improves symptoms in a majority of patients for whom medical treatment has failed. In rhinosinusitis patients, endoscopic sinus surgery aims to alleviate obstruction and re-establish mucociliary clearance. Surgery alters the structure-function relationship within the nasal passage, which is difficult to assess clinically. Computational modelling has been used to investigate this relationship by simulating air flow and environmental variables inside realistic three-dimensional models of the human nasal airway but many questions remain unanswered and need further investigation. The application of computational models to improve pre-surgical planning and post-surgical treatment may not be currently possible due to the absence of knowledge correlating the model-predicted parameters to physiological variables. Links between these parameters to patient outcomes are yet to be established. This article reviews the recent application of computational modelling to understand the nasal structure-function relationship following surgery in patients with sinusitis and nasal obstruction.

Environmental Triggers Associated With Empty Nose Syndrome Symptoms: A Cross-Sectional Study

OBJECTIVES

Empty nose syndrome (ENS) is thought to have multiple etiologies, one of which is a postsurgical phenomenon resulting from excessive loss of nasal tissues, particularly the inferior turbinate. Given that the inferior turbinate is instrumental in maintaining nasal homeostasis in different environments, it is believed that ENS symptoms arise only in more arid regions of the world. The aim of this study was to recruit an international population of individuals with ENS to investigate the association of local climate factors on the incidence and severity of ENS-specific symptoms.

METHODS

A cross-sectional study was performed of individuals from an international ENS database. ENS status was determined on the basis of a positive ENS questionnaire score (Empty Nose Syndrome 6-Item Questionnaire) and sinus computed tomographic imaging with supporting medical documentation. Participants completed a survey encompassing demographic, geographic, and symptom indicators. Climate variables were collected from global climate databases. Participant location was classified according to the Köppen-Geiger climate system. Pearson correlation analysis was performed using α = 0.05 to determine significance.

RESULTS

Fifty-three individuals with ENS were included. Participants were distributed across 5 continents and 15 countries (representing 4 distinct Köppen-Geiger zones). Although local climate factors varied significantly within this cohort, no significant association was found between Empty Nose Syndrome 6-Item Questionnaire symptom severity and these climate factors. However, most study participants reported exacerbation of their ENS symptoms in response to dry air (94%), air conditioning (64%), changes in season and weather (60%), and transitioning between indoors and outdoors (40%). This suggests that everyday local environmental factors may influence the well-being of these patients more than global, climate-level shifts.

CONCLUSIONS

ENS symptom severity does not appear to be related to climate or geographic factors. These findings deviate from the traditional dogma that ENS is experienced only in arid regions (or precluded in humid regions) and highlight the importance of recognizing this condition independent of geographic location.

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.

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.

Management of maxillary sinus inverted papilloma via endoscopic partial medial maxillectomy with an inferior turbinate reversing approach

The aim of this study is to evaluate the efficacy of endoscopic treatment for maxillary inverted papilloma (IP) through partial medial maxillectomy with an inferior turbinate reversing approach. A retrospective analysis of patients treated in our institution for maxillary sinus IP between July 2011 and August 2015 was performed. Demographics, operative technique, characteristics of tumors, complications, postoperative follow-up, and recurrence were evaluated. Twenty-two patients were enrolled in the study. All tumor attachments were identified intraoperatively. Adequate visualization was obtained following our approach. All inferior turbinate and nasolacrimal ducts were preserved. The median follow-up time was 41 months. One recurrence occurred at the follow-up time of 27 months. Postoperative hemorrhage and numbness at the ipsilateral frontal teeth were reported in two and one patients, respectively. Endoscopic surgery through partial medial maxillectomy using an inferior turbinate reversing approach provides full access to the maxillary sinus and preserves the inferior turbinate and nasolacrimal duct.

Radiofrequency volumetric inferior turbinate reduction: long-term clinical results

The aim of our study was to assess long-term results of radiofrequency volumetric tissue reduction of inferior turbinates (RVTR). We performed a prospective long-term longitudinal evaluation of 305 patients affected by rhinitis (114 allergic and 191 non-allergic) who were unresponsive to medical treatment and underwent RVTR (January 2004 - December 2010). Subjects were followed for a mean period of 39.70 ± 19.41 months (range 24-60). Patients completed the NOSE-scale questionnaire pre- and post-operatively after 1 month and yearly for 5-years. Recurrence was assumed if the post-operative total NOSE score increased by at least 75% during follow-up and the patient restarted medical treatments. Estimation of relapse over time was performed by Kaplan-Meyer analyses. We documented overall good satisfaction of patients regarding the procedure, with a good rate of pain control and a low rate of complications. Post-operatively there was a significant improvement in nasal stuffiness, nasal obstruction and mouth breathing (p < 0.05). We observed a worsening trend for symptoms after 36 months with progressive increasing rate of recurrences that were significantly higher in allergic than non-allergic patients (p < 0.05). We also observed a slight worsening trend of global satisfaction of patients. Our study confirms the minor discomfort and low risk of side effects of RVTR. Our data showed good efficacy of the procedure in the majority of patients for at least 36 months after surgery, and in fact in this time period the cumulative probability to remain relapse-free was up to 0.8. In the following 2 years, we observed a worse temporal trend in term of recurrence rate, and in particular in allergic patients with a significant difference vs non-allergic individuals (p < 0.05).

"TuNa-saving" endoscopic medial maxillectomy: a surgical technique for maxillary inverted papilloma

The maxillary sinus is the most common site of sinonasal inverted papilloma. Endoscopic sinus surgery, in particular endoscopic medial maxillectomy, is currently the gold standard for treatment of maxillary sinus papilloma. Although a common technique, complications such as stenosis of the lacrimal pathway and consequent development of epiphora are still possible. To avoid these problems, we propose a modification of this surgical technique that preserves the head of the inferior turbinate and the nasolacrimal duct. A retrospective analysis was performed on patients treated for maxillary inverted papilloma in three tertiary medical centres between 2006 and 2014. Pedicle-oriented endoscopic surgery principles were applied and, in select cases where the tumour pedicle was located on the anterior wall, a modified endoscopic medial maxillectomy was carried out as described in this paper. From 2006 to 2014 a total of 84 patients were treated. A standard endoscopic medial maxillectomy was performed in 55 patients (65.4%), while the remaining 29 (34.6%) had a modified technique performed. Three recurrences (3/84; 3.6%) were observed after a minimum follow-up of 24 months. A new surgical approach for select cases of maxillary sinus inverted papilloma is proposed in this paper. In this technique, the endoscopic medial maxillectomy was performed while preserving the head of the inferior turbinate and the nasolacrimal duct ("TuNa-saving"). This technique allowed for good visualization of the maxillary sinus, good oncological control and a reduction in the rate of complications.

The impact of endoscopic sinus surgery on paranasal physiology in simulated sinus cavities

BACKGROUND

Surgery improves symptoms for the majority of chronic rhinosinusitis (CRS) patients; however, physiological changes in the sinus cavities remain poorly characterized. Direct measurement of changes in airflow, pressure, temperature, humidity, and intranasal spray distribution following surgery is technically challenging. Accordingly, we have used computational fluid dynamic modeling to quantify how these parameters change postoperatively.

METHODS

Computed tomography images from a normal control, a patient with CRS preoperatively and postoperatively, and a patient following an endoscopic Lothrop procedure (ELP) were used to create 4 three-dimensional models of the sinus cavities. Changes in physiologic parameters and topical drug distribution were modeled (inhaled air at 16°C and 10% humidity) at the maxillary ostium, frontal recess, and sphenoid ostium.

RESULTS

Large differences were seen between models. Following surgery, the maxillary ostia were found on average to be cooler (by 2.4°C), with an increased airflow (0.26 m/second; from 0 m/second), and a 9% reduction in absolute humidity. Sphenoid ostial parameters followed a similar trend. Significant changes in frontal recess physiology were seen following ELP in which the recess was 4.2°C cooler, had increased airflow (0.76 m/second) and a 17% reduction in absolute humidity. Topical drug distribution increased with surgery, particularly after ELP.

CONCLUSION

Surgery changes the geometry and physiology of the paranasal sinuses. These changes are likely to have an impact on wound healing, mucociliary function, and microbial ecology in postoperative cavities. Application of this model to further understand the effects of surgery may help to optimize surgical techniques and improve topical drug delivery.

Impact of nasal septal perforations of varying sizes and locations on the warming function of the nasal cavity: A computational fluid-dynamics analysis of 5 cases

Patients with a nasal septal perforation often exhibit symptoms associated with disturbed airflow, which can have an adverse effect on the warming function of the nasal cavity. The impact of this effect is not fully understood. The warming function is an important factor in the maintenance of nasal physiology. We conducted a study to investigate the impact of septal perforations of various sizes and locations on the warming function during inspiration in 5 patients-3 men and 2 women, aged 25 to 47 years. Three-dimensional computed tomography and computational fluid dynamics were used to model the flux of communication and temperature, and differences among patients were compared. All 5 patients exhibited an impairment of their nasal warming function. As the size of the perforation increased, the flux of communication increased and the warming function decreased. Perforations located in an anterior position were associated with greater damage to the warming function than those in a posterior position. In patients with a large or anteriorly located perforation, airflow temperature in the nasopharynx was decreased. Our findings suggest that septal perforations not only induce airflow disturbance, but they also impair the nasal warming function. Further analysis of warming function is necessary to better explore flow mechanisms in patients with structural abnormalities.

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.

Characterization of postoperative changes in nasal airflow using a cadaveric computational fluid dynamics model: supporting the internal nasal valve

IMPORTANCE

Collapse or compromise of the internal nasal valve (INV) results in symptomatic nasal obstruction; thus, various surgical maneuvers are designed to support the INV.

OBJECTIVE

To determine the effect on nasal airflow after various surgical techniques focused at the level of the INV and lateral nasal sidewall.

DESIGN AND SETTING

A fresh cadaver head was obtained and underwent suture and cartilage graft techniques directed at the level of the INV using an external approach. Preoperative and postoperative digital nasal models were created from the high-resolution, fine-cut, computed tomographic imaging after each intervention. Isolating the interventions to the level of the INV, we used computational fluid dynamic techniques to calculate nasal resistance, nasal airflow, and nasal airflow partitioning for each intervention.

INTERVENTION

Suture and cartilage graft techniques.

MAIN OUTCOMES AND MEASURES

Nasal airflow, nasal resistance, and partitioning of airflow.

RESULTS

Using the soft-tissue elevation model as baseline, computational fluid dynamic analysis predicted that most of the suture and cartilage graft techniques directed toward the nasal valve improved nasal airflow and partitioning while reducing nasal resistance. Specifically, medial and modified flare suture techniques alone improved nasal airflow by 16.9% and 15.1%, respectively. The combination of spreader grafts and modified flare suture improved nasal airflow by 13.2%, whereas spreader grafts alone only improved airflow by 5.9%. The largest improvements in bilateral nasal resistance were achieved using the medial and modified flare sutures, outperforming the combination of spreader grafts and modified flare suture.

CONCLUSIONS AND RELEVANCE

Techniques directed at supporting the INV have tremendous value in the treatment of nasal obstruction. The use of flare sutures alone can address dynamic valve collapse or upper lateral cartilage incompetence without gross disruption of the nasal architecture. Using computational fluid dynamic techniques, this study suggests that flare sutures alone may improve flow and reduce resistance when placed medially, surpassing spreader grafts alone or in combination with flare sutures. The longevity of these maneuvers can only be assessed in the clinical setting. Studies in additional specimens and clinical correlation in human subjects deserve further attention and investigation.

LEVEL OF EVIDENCE

NA.

Identifying patients who may benefit from inferior turbinate reduction using computer simulations

OBJECTIVES/HYPOTHESIS

(1) To determine objective criteria to predict which patients may benefit most from inferior turbinate reduction surgery. (2) To test whether the site of turbinate reduction, either along the nasal floor (bottom resection) or along the septal side (medial resection), impacts the extent to which nasal resistance is reduced.

STUDY DESIGN

Case series.

METHODS

Three-dimensional reconstructions of the nasal anatomy of five nasal airway obstruction patients were created based on presurgical computed tomography scans. Inferior turbinate reduction models were created for each patient using virtual surgery. Airflow, heat transfer, and humidity transport during inspiration were simulated using computational fluid dynamics (CFD).

RESULTS

Nasal resistance curves revealed little to no difference between bottom resection and medial resection models. In two patients, little change was observed in nasal resistance after virtual inferior turbinate reduction, which was attributed to the narrowest cross-sections being restricted to the anterior nose (i.e., anterior to the inferior turbinate). The three patients whose nasal resistances decreased substantially after virtual inferior turbinate reduction had a narrower airspace in the turbinate region and higher nasal resistance presurgery. Nasal air conditioning capacity was more affected by medial resections.

CONCLUSIONS

CFD simulations predicted no significant difference in the decrease in nasal resistance between virtual inferior turbinate reductions performed by bottom versus medial resection of the turbinate. However, bottom resections better preserved the calculated humidification efficiency. The simulations predicted that the greatest reduction in nasal resistance occurs in patients with the highest presurgical resistance in the turbinate region.

LEVEL OF EVIDENCE

4.

Numerical investigation of the flow field in realistic nasal septal perforation geometry

The computational fluid dynamics (CFD) are used to evaluate the physiological function of the nose. We evaluated the aerodynamics of the nasal cavity in a patient with septal perforation (SP), pre- and postvirtual repair. Three-dimensional nasal models were reconstructed, and then a wide range of the pressure drops and flow rates were analyzed. The airflow velocity is higher in the central region and is lower around the boundary of the SP. The air velocity in the SP increases as the pressure drop increases. Furthermore, at the anterior part of the SP, the shear stress is higher in the upper part. In addition, the repair of SP does not affect the total nasal airflow rate and the velocity contour patterns. The potential usage of the CFD technique as a predictive technique to explore the details and a preoperative assessment tool to help in clinical decision making in nasal surgery is emphasized.

Endoscopic medial maxillectomy with preservation of inferior turbinate and nasolacrimal duct

BACKGROUND

Endoscopic medial maxillectomy (EMM) is a safe and effective procedure for treatment of inverted papilloma (IP) originating from the maxillary sinus. However, EMM usually removes the inferior turbinate and nasolacrimal duct. The inferior turbinate has a critical function in conditioning of the nasal airflow, and resection of the nasolacrimal ducts has a risk of epiphora. We developed a newly derived surgical technique, endoscopic modified medial maxillectomy (EMMM), which enables preservation of the inferior turbinate and nasolacrimal duct.

METHODS

A retrospective case series of six patients with IP and nine patients with mucoceles of the maxillary sinus after a Caldwell-Luc operation, who underwent surgery using the EMMM technique, were reviewed.

RESULTS

In patients with IP, there were no recurrences for a mean follow-up of 16.7 months. Eight of nine patients with mucoceles of the maxillary sinus showed patency. All patients showed preservation of the inferior turbinate. One patient with mucocele was referred for dacryocystorhinostomy because of epiphora.

CONCLUSION

EMMM produces access to the maxillary sinus identically to conventional EMM, despite preservation of the inferior turbinate and nasolacrimal duct.

Deviated nasal septum hinders intranasal sprays: a computer simulation study

BACKGROUND

This study investigates how deviated nasal septum affects the quantity and distribution of spray particles, and examines the effects of inspiratory airflow and head position on particle transport.

METHODS

Deposition of spray particles was analysed using a three-dimensional computational fluid dynamics model created from a computed tomography scan of a human nose with leftward septal deviation and a right inferior turbinate hypertrophy. Five simulations were conducted using FluentTM software, with particle sizes ranging from 20-110 &#956;m, a spray speed of 3 m/s, plume angle of 68(deg), and with steady state inspiratory airflow either present (15.7 L/min) or absent at varying head positions.

RESULTS

With inspiratory airflow present, posterior deposition on the obstructed side was approximately four times less than the contralateral side, regardless of head position, and was statistically significant. When airflow was absent, predicted deposition beyond the nasal valve on the left and right sides were between 16% and 69% lower and positively influenced by a dependent head position.

CONCLUSION

Simulations predicted that septal deviation significantly diminished drug delivery on the obstructed side. Furthermore, increased particle penetration was associated with presence of nasal airflow. Head position is an important factor in particle deposition patterns when inspiratory airflow is absent.

Radiofrequency volume turbinate reduction versus partial turbinectomy: clinical and histological features

BACKGROUND

Nasal obstruction is a common symptom related to turbinate hypertrophy in 20% of cases. When medical treatment failed different surgical options were available. Actually, nasal physiology impairment after surgical treatment is not fully clear. This study evaluates microscopic mucosal changes and physiological function, by means of mucociliary transport time (MCT), after radiofrequency volume turbinate reduction and partial inferior turbinectomy.

METHODS

Forty-eight nonallergic patients were treated for chronic nasal obstruction. Twenty-six patients (group A) underwent radiofrequency turbinate reduction and 22 patients (group B) underwent partial turbinectomy associated with septoplasty. Mucosal specimens obtained before T(0) and 6 months (T(1)) after surgery were compared by means of optical microscope and transmission electron microscope. All patients were evaluated using MCT at T(0) and T(1).

RESULTS

Optical analysis showed circumscribed squamous metaplasia and fibrosis in specimens obtained from group A. Same changes were more evident in group B. Ultrastructural analysis evidenced loss of ciliated epithelium in group B, whereas in group A a normal number of cilia was found. In all patients at T(1), MCT time was prolonged in comparison with the preoperative values. After surgery, group B showed significantly prolonged MCT in comparison with group A (p < 0.05).

CONCLUSION

In our study both surgical techniques achieved good clinical outcomes with improved nasal function, although the ciliated epithelium appeared partially impaired. These findings resulted in a prolonged MCT in all patients, especially in those treated with partial turbinectomy. Compared to partial resection, intraturbinal turbinate reduction seems to be the method of choice to better preserve nasal physiology.

Nasal mucosa temperature as a marker of disease in children with allergic rhinitis

BACKGROUND

Allergic rhinitis (AR) is a symptomatic disorder of the nose induced after allergen exposure by an IgE-mediated inflammation of the nasal mucosa. This study was designed to investigate the role of nasal mucosa temperature in AR.

METHODS

We investigated the relationship between eosinophilic infiltration, nasal obstruction, and nasal mucosa temperature in 35 children with rhinitis aged 6-12 years.

RESULTS

A significant relationship was shown between nasal temperature values and eosinophil infiltration at nasal cytology (p < 0.01). Nasal temperature was also significantly associated with nasal obstruction, assessed in terms of nasal volume (Vol [2-5 cm]; p < 0.05) and minimum cross-sectional area (p < 0.01). No significant correlation emerged between the degree of nasal obstruction and presence of eosinophils at nasal cytology (p > 0.05).

CONCLUSION

These results suggest a relationship between nasal temperature and nasal mucosa inflammation and obstruction.

Impacts of fluid dynamics simulation in study of nasal airflow physiology and pathophysiology in realistic human three-dimensional nose models

During the past decades, numerous computational fluid dynamics (CFD) studies, constructed from CT or MRI images, have simulated human nasal models. As compared to rhinomanometry and acoustic rhinometry, which provide quantitative information only of nasal airflow, resistance, and cross sectional areas, CFD enables additional measurements of airflow passing through the nasal cavity that help visualize the physiologic impact of alterations in intranasal structures. Therefore, it becomes possible to quantitatively measure, and visually appreciate, the airflow pattern (laminar or turbulent), velocity, pressure, wall shear stress, particle deposition, and temperature changes at different flow rates, in different parts of the nasal cavity. The effects of both existing anatomical factors, as well as post-operative changes, can be assessed. With recent improvements in CFD technology and computing power, there is a promising future for CFD to become a useful tool in planning, predicting, and evaluating outcomes of nasal surgery. This review discusses the possibilities and potential impacts, as well as technical limitations, of using CFD simulation to better understand nasal airflow physiology.

Computed nasal resistance compared with patient-reported symptoms in surgically treated nasal airway passages: a preliminary report

BACKGROUND

Nasal airway obstruction (NAO) is a common health condition impacting mood, energy, recreation, sleep, and overall quality of life. Nasal surgery often addresses NAO but the results are sometimes unsatisfactory. Evaluating surgical treatment efficacy could be improved if objective tests were available that correlated with patient-reported measures of symptoms. The goal of this study was to develop methods for comparing nasal resistance computed by computational fluid dynamics (CFD) models with patient-reported symptoms of NAO using early data from a 4-year prospective study.

METHODS

Computed tomography (CT) scans and patient-reported scores from the Nasal Obstruction Symptom Evaluation (NOSE) scale and a visual analog scale (VAS) measuring unilateral airflow sensation were obtained pre- and postoperatively in two NAO patients showing no significant mucosal asymmetry who were successfully treated with functional nasal surgery, including septoplasty. Pre- and postsurgery CFD models were created from the CT scans. Numerical simulation of steady-state inspiratory airflow was used to calculate bilateral and unilateral CFD-derived nasal resistance (CFD-NR).

RESULTS

In both subjects, NOSE and VAS scores improved after surgery, bilateral CFD-NR decreased, and unilateral CFD-NR decreased on the affected side. In addition, NOSE and VAS scores tracked with unilateral CFD-NR on the affected side.

CONCLUSION

These preliminary results suggest a possible correlation between unilateral NR and patient-reported symptoms and imply that analysis of unilateral obstruction should focus on the affected side. A formal investigation of unilateral CFD-NR and patient-reported symptoms in a series of NAO patients is needed to determine if these variables are correlated.

Effects of single-sided inferior turbinectomy on nasal function and airflow characteristics

Knowledge of airflow characteristics in the nasal cavity is essential to understanding the physiologic and pathologic aspects of nasal breathing. Airflows inside post-surgery models were investigated both experimentally and numerically to simulate the inferior turbinectomy. The left cavities of all three models are normal and right cavity is modified by (1) excision of the head of the inferior turbinate, (2) resection of the lower fifth of the inferior turbinate, and (3) resection of almost the entire inferior turbinate. Thin-slice CT (computed tomography) data (0.6mm deep) and meticulous refinement of the model surface by over a decade-long collaboration between engineers and an experienced ENT doctor resulted in the creation of sophisticated nasal cavity models. After numerical experiments and validation by comparison with the PIV results, the CFD code using the Reynolds stress turbulent model and variable temperature boundary condition on the mucosal wall was chosen as the proper numerical framework. Both global quantities (pressure drop, flow rate ratio, total wall heat transfer) and local changes (velocity, temperature, humidity, pressure gradient, and wall shear stress) were numerically investigated. The turbinectomy obviously altered the main stream direction. The flow rate in the upper airway near the olfactory slit decreased in models (1) and (3). This may weaken the olfactory function of the nose. Fluid and thermal properties that are believed to be related with physiology and prognosis are dependent on turbinate resection volume, position, and manner. Widening of the inferior airway does not always result in decreased flow resistance or wall heat transfer. The gains and losses of inferior turbinectomy were considered by analysis of the post-surgery model results. Nasal resistance was increased in model (1) due to sudden airway expansion. Nasal resistance increased and the wall heat transfer decreased in model (3) due to sudden airway expansion and excessive reduction of the mucosal wall surface area. Local shear stress and pressure gradient levels were increased in models (1) and (3).

Correlation of nasal morphology to air-conditioning and clearance function

Nasal morphology plays an important functional role in the maintenance of upper airway health. Identification of functional regions, based on morphological attributes, assists in correlating location to primary purpose. The effects of morphological variation on heat and water mass transport in congested and patent nasal airways were investigated by examining nasal cross-sectional MRI images from 8 healthy subjects. This research confirms the previous identification of functional air-conditioning regions within the nose. The first is the anterior region where the morphology prevents over-stressing of tissue heat and fluid supply near the nares. The second is the mid region where low flow velocity favours olfaction and particle deposition. The third is the posterior region which demonstrates an increase in heat and water mass flux coefficients to compensate for rising air humidity and temperature. Factors identified within the congested airway that favour enhanced mucocillary clearance were also identified.