Septal deviation and nasal resistance: an investigation using virtual surgery and computational fluid dynamics

Comparing Patient-Reported Outcomes with Computational Fluid Dynamics-Derived Nasal Airflow After Nasal Airway Surgery: Prioritizing the Patient's Perception of Nasal Obstruction

Background: Some patients report persistent nasal obstruction after surgical treatment despite objective improvement. Objective: To compare patients' perceptions of nasal obstruction after surgery with objective nasal airflow as determined by computational fluid dynamics (CFD) modeling: (1) Is perception driven by a more symptomatic side? (2) Can symptom improvement be predicted with CFD modeling? Methods: Pre/postoperative Nasal Obstruction Symptom Evaluation (NOSE) and visual analog scale (VAS) score were collected for patients undergoing nasal obstruction surgery. Pre/postoperative computed tomography was used to generate patient-specific airway models for CFD simulation at 15 L/min resting inspiration. Results: Ten patients (22-53 years, seven men and three women) underwent septoplasty, turbinate reduction, and/or rhinoplasty. Postoperative NOSE was most correlated with postoperative VAS score from the "affected" side (R2 = 0.59, p < 0.01), and postoperative NOSE was strongly predicted by a two-parameter model using parameters only from the "affected" side (R2 = 0.84, adjusted R2 = 0.80, p < 0.01). Conclusion: The postoperative state of the initially "affected" side drives outcomes after nasal obstruction surgery. Surgeries should prioritize improving the "affected" side. A two-parameter model using the VAS and nasal airflow from only the "affected" side strongly predicts NOSE and is promising for the future using virtual planning to individualize procedures to optimize outcome.

Quantifying the Subjective Experience of Nasal Obstruction: A Review

Nasal obstruction is an exceedingly common problem and challenging to treat due to its multifactorial etiology. Therefore, measuring treatment outcomes of nasal obstruction can be equally complex yet vital to appropriately assessing symptom improvement or resolution. Both physiologic and anatomic assessments of the nasal airway exist in addition to validated patient-reported outcome measures (PROMs), which objectify subjective nasal obstruction and sinonasal symptoms. Correlation between objective and subjective treatment outcome measures is controversial with clinical guidelines favoring the use of PROMs for surgical treatment of nasal obstruction. In this review, the anatomic and physiologic measurements of the nasal airway and validated PROMs will be discussed, as well as the rationale for implementing PROMs into the rhinoplasty surgeon's practice.

Effects of Mucosal Decongestion on Nasal Aerodynamics: A Pilot Study

OBJECTIVE

Mucosal decongestion with nasal sprays is a common treatment for nasal airway obstruction. However, the impact of mucosal decongestion on nasal aerodynamics and the physiological mechanism of nasal airflow sensation are incompletely understood. The objective of this study is to compare nasal airflow patterns in nasal airway obstruction (NAO) patients with and without mucosal decongestion and nondecongested healthy subjects.

STUDY DESIGN

Cross-sectional study of a convenience sample.

SETTING

Academic tertiary medical center.

METHODS

Forty-five subjects were studied (15 nondecongested healthy subjects, 15 nondecongested NAO patients, and 15 decongested NAO patients). Three-dimensional models of the nasal anatomy were created from computed tomography scans. Steady-state simulations of airflow and heat transfer were conducted at 15 L/min inhalation rate using computational fluid dynamics.

RESULTS

In the narrow side of the nose, unilateral nasal resistance was similar in decongested NAO patients and nondecongested healthy subjects, but substantially higher in nondecongested NAO patients. The vertical airflow distribution within the nasal cavity (inferior vs middle vs superior) was also similar in decongested NAO patients and nondecongested healthy subjects, but nondecongested NAO patients had substantially less middle airflow. Mucosal cooling, quantified by the surface area where heat flux exceeds 50 W/m2, was significantly higher in decongested NAO patients than in nondecongested NAO patients.

CONCLUSION

This pilot study suggests that mucosal decongestion improves objective measures of nasal airflow, which is consistent with improved subjective sensation of nasal patency after decongestion.

Computational Fluid Dynamics and Its Potential Applications for the ENT Clinician

This article is an examination of computational fluid dynamics in the field of otolaryngology, specifically rhinology. The historical development and subsequent application of computational fluid dynamics continues to enhance our understanding of various sinonasal conditions and surgical planning in the field today. This article aims to provide a description of computational fluid dynamics, the methods for its application, and the clinical relevance of its results. Consideration of recent research and data in computational fluid dynamics demonstrates its use in nonhistological disease pathology exploration, accompanied by a large potential for surgical guidance applications. Additionally, this article defines in lay terms the variables analyzed in the computational fluid dynamic process, including velocity, wall shear stress, area, resistance, and heat flux.

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.

Olfactory drug delivery with intranasal sprays after nasal midvault reconstruction

Conductive olfaction and nose to brain drug delivery are important processes that remain limited by inadequate odorant or drug delivery to the olfactory airspace. Primary challenges include anatomic barriers and poor targeting to the olfactory region. This study uses computational fluid dynamics to investigate the effects of nasal midvault surgery on olfactory drug delivery with intranasal sprays. Soft tissue elevation, spreader flaps, and spreader grafts were performed on two fresh cadaveric specimens, using computed tomography for airway reconstruction. Nasal airflow and drug particle transport simulations were performed under these conditions: inhalation rate (15, 30 L/min), spray velocity (1, 5, 10 m/s), spray location (top, bottom, center, medial, lateral), head position (upright, supine, forward, backward), and particle size (1-100 µm). Simulation results were used to calculate drug particle deposition to the olfactory airspaces and bulbs. Total olfactory deposition was < 5% but attained a maximum of 36.33% when sorted by particle size. There was no association between nasal midvault surgery and olfactory deposition. No single parameter or technique demonstrated superior olfactory deposition, but smaller particle size, slower spray velocity, and higher inhalation rate tended to optimize olfactory deposition, providing important implications for future intranasal spray and drug design to target the olfactory airspace.

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.

Effect of different degrees of adenoid hypertrophy on pediatric upper airway aerodynamics: a computational fluid dynamics study

To improve the diagnostic accuracy of adenoid hypertrophy (AH) in children and prevent further complications in time, it is important to study and quantify the effects of different degrees of AH on pediatric upper airway (UA) aerodynamics. In this study, based on computed tomography (CT) scans of a child with AH, UA models with different degrees of obstruction (adenoidal-nasopharyngeal (AN) ratio of 0.9, 0.8, 0.7, and 0.6) and no obstruction (AN ratio of 0.5) were constructed through virtual surgery to quantitatively analyze the aerodynamic characteristics of UA with different degrees of obstruction in terms of the peak velocity, pressure drop (△P), and maximum wall shear stress (WSS). We found that two obvious whirlpools are formed in the anterior upper part of the pediatric nasal cavity and in the oropharynx, which is caused by the sudden increase in the nasal cross-section area, resulting in local flow separation and counterflow. In addition, when the AN ratio was ≥ 0.7, the airflow velocity peaked at the protruding area in the nasopharynx, with an increase 1.1-2.7 times greater than that in the nasal valve area; the △P in the nasopharynx was significantly increased, with an increase 1.1-6.8 times greater than that in the nasal cavity; and the maximum WSS of the posterior wall of the nasopharynx was 1.1-4.4 times larger than that of the nasal cavity. The results showed that the size of the adenoid plays an important role in the patency of the pediatric UA.

Is septoplasty required whenever anterior septal deviation is present?

OBJECTIVE

Post-operative success and patient satisfaction were assessed following septoplasty for mild to severe anterior septal deviation.

METHODS

The study included patients with an anterior nasal septal deviation in the form of a 'C' shape and close to the nasal valve in the anterior septal area. Deviation severity was classified as severe (group 1), moderate (group 2) or mild (group 3). Open or closed septoplasty procedures were performed. All patients were surveyed twice using the Nasal Obstruction Symptom Evaluation scale and the 36-Item Short Form Health Survey.

RESULTS

The mean Nasal Obstruction Symptom Evaluation score for group 1 was 15.58 ± 2.34 prior to surgery and 6.61 ± 3.29 following surgery. The corresponding pre- and post-surgery scores in group 2 were 11.9 ± 2.82 and 6.3 ± 3.03, respectively. In group 3, these values were 8.28 ± 2.63 and 7.12 ± 3.18, respectively. The mean 36-Item Short Form Health Survey physical function value for groups 1 and 2 increased after surgery; in group 3, this value decreased after surgery, but the result was not statistically significant.

CONCLUSION

Septoplasty is very successful for treating moderate or advanced deviations, but great care should be taken when employing septoplasty for mild deviations.

Changes in nasolabial angle may alter nasal valve morphology and airflow: a computational fluid dynamics study

Aim: Nasal valve (NV) dysfunctions are a significant cause of nasal obstruction. Changes in the nasolabial angle (NLA) may also cause changes in NV morphology. The effect of changes in the 3D structure of the nasal valve region (NVR) on nasal airflow has yet to be studied sufficiently. The accuracy of computational fluid dynamics (CFD) simulation results of nasal airflow has been confirmed by in vitro tests. Therefore, this study aimed to evaluate the effect of changes in NV structure and volume on nasal airflow based on the CFD method. Material and Method: We used CT images to create a 3D structural model of the NVR. First, CT images were transferred to MIMICS® software, and the nasal air passage was modeled. A solid reference model of the NVR was then created using SolidWorks software. Five different solid 3D nasal valve models were created with nasolabial angles of 85˚ in Model 1, 90˚ in Model 2, 95˚ in Model 3, 100˚ in Model 4, and 105˚ in Model 5. To simulate breathing during rest and exercise using the CFD method, the unilateral nasal airflow rates were set at 150 ml/s and 500 ml/s, respectively. The CFD method was then used to calculate each model’s airflow properties. Finally, the volumes of the models, pressure at the NV outlet, and airflow velocity were evaluated and calculated to investigate each model’s NV airflow characteristics. Results: Our study found a significant correlation between the nasolabial angle (NLA) and NVR volume (r=-0.998, p=0.000), flow rate and velocity (r=0.984, p=0.000), velocity and maximum pressure (r=0.920, p=0.000), velocity and minimum pressure (r=-0.969, p=0.000), flow rate and maximum pressure (r=0.974, p=0.000), and flow rate and minimum pressure (r=-0.950, p=0.000). There was no correlation between NLA increase and nasal airflow velocity. We determined that the highest pressure and lowest airflow velocity values were in the upper angle region and that the lowest pressure and highest airflow velocity values were at the bottom of the NVR in all models. Conclusion: Using the CFD method, we found a decrease in NVR volume and an increase in airflow velocity with an increase in NLA. In addition, we found that the pressure values in the NVR did not change significantly with the increase in NLA.

Fashioned Mucoperichondrial Flap Technique Versus Fishing Line Technique in the Repair of Septal Dislocation: A Prospective Comparative Study

BACKGROUND

A nasal septal dislocation is a common form of septal deviation with many challenges and different surgical techniques for correction.

OBJECTIVE

To assess the efficacy of fashioned mucoperichondrial flap technique versus fishing line technique in the repair of septal dislocation.

METHODS

The study was a prospective comparative cohort study conducted on 88 patients aged above 18 years who have symptomatic mild to moderate caudal septal dislocation spanning the period from June 2021 to June 2022. Preoperatively, all patients were evaluated by the Nasal Obstruction and Septoplasty Effectiveness (NOSE) scale to assess the degree of nasal obstruction. Anterior rhinoscopy and endoscopic examination of the nose were done for every patient to assess the degree of obstruction, whether mild, moderate, or severe. Outcomes included an assessment of both techniques' efficacy in managing nasal obstruction as expressed by the NOSE scale and comparing both techniques regarding the operative and postoperative details.

RESULTS

The current study showed a highly significant improvement in the NOSE scale postoperatively in both groups (P < .00001 for both groups). The mean operative duration for group I was significantly less than that for group II (P < .00001). There was a nonsignificant difference between both groups regarding the postoperative NOSE scale, and postoperative degree of obstruction (P = .066 and .56, respectively). Regarding postoperative complications, there was a nonsignificant difference between both groups except for patient discomfort as assessed 1 week postoperatively. Group II showed significantly more patient discomfort (P = .02), which improved 4 weeks postoperatively.

CONCLUSION

Both techniques presented in this study effectively corrected mild and moderate caudal septal dislocation with significant improvement of nasal obstruction postoperatively. Both techniques produced good esthetic outcomes and were associated with few comparable complications in both groups.

Anatomic Optical Coherence Tomography (aOCT) for Evaluation of the Internal Nasal Valve

OBJECTIVES/HYPOTHESIS

To establish the utility of anatomic optical coherence tomography (aOCT) in evaluating internal nasal valve (INV).

STUDY DESIGN

Anatomic specimen imaging study.

METHODS

Fresh-harvested human specimen heads were evaluated using both computed tomography (CT) imaging as well as using aOCT. Scans were performed at three time points: 1) After septoplasty for cartilage harvest, 2) after placement of butterfly graft (BFG), and 3) after placement of bilateral spreader grafts (SG). Imaging data were then converted into 3D models of the nasal airway. CT- and aOCT-generated models were compared by both static volumetric analysis and computational fluid dynamics (CFD) to predict nasal resistance and pressure.

RESULTS

Scans using aOCT showed comparable results to CT in terms of volumetric parameters both before and after intervention. Analysis of aOCT data by CFD demonstrated decrease in pressure after SG or BFG intervention. No statistically significant difference was observed when comparing CT- and aOCT-generated calculations of pressure or resistance.

CONCLUSION

The INV can be imaged in a static fashion using aOCT technology. Advantages over traditional CT imaging include lack of exposure to radiation and rapid scan time. In addition, in-office use is possible as aOCT technology develops. Further investigation will be necessary to define the role of aOCT in the dynamic evaluation of this vital component of the nasal airway.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:2148-2156, 2022.

Correlation of Nasal Mucosal Temperature and Nasal Patency—A Computational Fluid Dynamics Study

OBJECTIVES

Recent evidence suggests that detection of nasal mucosal temperature, rather than direct airflow detection, is the primary determinant of subjective nasal patency. This study examines the role of nasal mucosal temperature in the perception of nasal patency using in vivo and computational fluid dynamics (CFD) measurements.

METHODS

Healthy adult participants completed Nasal Obstruction Symptom Evaluation (NOSE) and Visual Analogue Scale (VAS) questionnaires. A temperature probe measured nasal mucosal temperature at the vestibule, inferior turbinate, middle turbinate, and nasopharynx bilaterally. Participants underwent a CT scan, used to create a 3D nasal anatomy model to perform CFD analysis of nasal mucosal and inspired air temperature and heat flux along with mucosal surface area where heat flux >50 W/m² (SAHF50).

RESULTS

Eleven participants with a median age of 27 (IQR 24; 48) were recruited. Probe-measured temperature values correlated strongly with CFD-derived values (r = 0.87, p < 0.05). Correlations were seen anteriorly in the vestibule and inferior turbinate regions between nasal mucosal temperature and unilateral VAS (r = 0.42-0.46; p < 0.05), between SAHF50 and unilateral VAS (r = -0.31 to -0.36; p < 0.05) and between nasal mucosal temperature and SAHF50 (r = -0.37 to -0.41; p < 0.05). Subjects with high patency (VAS ≤10) had increased heat flux anteriorly compared with lower patency subjects (VAS >10; p < 0.05).

CONCLUSION

Lower nasal mucosal temperature and higher heat flux within the anterior nasal cavity correlates with a perception of improved unilateral nasal patency in healthy individuals.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:1328-1335, 2023.

Characterizing the respiratory-induced mechanical stimulation at the maxillary sinus floor following sinus augmentation by computational fluid dynamics

Background: The relationship between maxillary sinus pneumatization and respiratory-induced fluid mechanics remains unclear. The purpose of this study was to simulate and measure the respiratory-induced mechanical stimulation at the sinus floor under different respiratory conditions and to investigate its potential effect on the elevated sinus following sinus-lifting procedures.

Methods: The nasal airway together with the bilateral maxillary sinuses of the selected patient was segmented and digitally modeled from a computed tomographic image. The sinus floors of the models were elevated by simulated sinus augmentations using computer-aided design. The numerical simulations of sinus fluid motion under different respiratory conditions were performed using a computational fluid dynamics (CFD) algorithm. Sinus wall shear stress and static pressure on the pre-surgical and altered sinus floors were examined and quantitatively compared.

Results: Streamlines with minimum airflow velocity were visualized in the sinus. The sinus floor pressure and the wall shear stress increased with the elevated inlet flow rate, but the magnitude of these mechanical stimulations remained at a negligible level. The surgical technique and elevated height had no significant influence on the wall pressure and the fluid mechanics.

Conclusion: This study shows that respiratory-induced mechanical stimulation in the sinus floor is negligible before and after sinus augmentation.

Caudal Septal Deviation: A Computed Tomography-Based Evaluation Method

OBJECTIVE

Caudal septal deviation (CSD) correction during septorhinoplasty is challenging, and various surgical modifications and evaluations remain controversial. This study aimed to introduce an objective evaluation method based on computed tomography (CT) images to measure the effectiveness of septorhinoplasty for CSD treatment.

METHODS

We retrospectively analyzed preoperative and postoperative CT images of patients who had undergone functional open septorhinoplasty by the plastic surgery and otorhinolaryngology teams between January and September 2019. Using OsiriX Lite (Pixmeo, Switzerland), CSD was calculated as the distance between the septum midline and palatal plane. Deformation was categorized as C-shaped unilateral or S-shaped bilateral deviations. The change in the distance between preoperative and postoperative images was considered because of surgical intervention.

RESULTS

Twenty patients (mean age, 35 years; 13 males [65%], 7 females [35%]) were included. The median deviation was 3.01 mm (range, 0.45-7.34 mm) preoperatively and 1.6 mm (range, 0.5-2.86 mm) postoperatively, indicating a reduction of 1.26 mm (median, P < 0.05) due to surgical intervention. C- and S-shaped deviations were seen preoperatively in 9 (45%) and 11 (55%) patients and postoperatively in 6 (30%) and 14 (70%) patients, respectively. The mean ± SD time of analysis was 7 ± 2.1 minutes.

CONCLUSIONS

Caudal septal deviation showed significant changes from preoperative to postoperative CT images, based on the distance between the actual septum midline and the constructed straight septum. This allowed effective evaluation of surgical efficacy for septum straightening. Although additional studies are needed, this method allows clearer stratification of surgical outcomes.

In-silico investigation of airflow and micro-particle deposition in human nasal airway pre- and post-virtual transnasal sphenoidotomy surgery

Sphenoid sinus, located posterior to the nasal cavity, is difficult to reach for a surgery. Several operation procedures are available for sphenoidotomy, including endoscopic surgeries. Although the endoscopic sinus surgery is minimally invasive with low post-operative side effects, further optimization is required. Transnasal sphenoidotomy is a low invasive alternative to transethmoidal sphenoidotomy, but it still needs to be studied to understand its effects on the airflow pattern and the particle deposition. In this work, we simulated airflow and the micro-particle deposition in the nasal airway of a middle-aged man to investigate the change in particle deposition in the sphenoid sinus after virtual transnasal sphenoidotomy surgery. The results demonstrated that after transnasal sphenoidotomy, particle deposition in the targeted sphenoid sinus was an order of magnitude lower than that observed after virtual transethmoidal sphenoidotomy surgery. In addition, the diameter of the particles for the peak deposition fraction in the targeted sinus was shifted to smaller diameters after the transnasal sphenoidotomy surgery compared with that in the post-transethmoidal condition. These results suggest that the endoscopic transnasal sphenoidotomy can be a better procedure for sphenoid surgeries as it decreases the chance of bacterial contaminations and consequently lowers the surgical side effects and recovery time.

Toward automatic atlas-based surgical planning for septoplasty

PURPOSE

Surgery for nasal airway obstruction (NAO) has a high failure rate, with up to 50% of patients reporting persistent symptoms postoperatively. Virtual surgery planning has the potential to improve surgical outcomes, but current manual methods are too labor-intensive to be adopted on a large scale. This manuscript introduces an automatic atlas-based approach for performing virtual septoplasties.

METHODS

A cohort of 47 healthy subjects and 26 NAO patients was investigated. An atlas of healthy nasal geometry was constructed. The automatic virtual septoplasty method consists of a multi-stage registration approach to fit the atlas to a target NAO patient, automatically segment the patient's septum and airway, and deform the patient image to have a non-deviated septum.

RESULTS

Our automatic virtual septoplasty method straightened the septum successfully in 18 out of 26 NAO patients (69% of cases). In these cases, the ratio of the higher to the lower airspace cross-sectional areas in the left and right nasal cavities improved from 1.47 ± 0.45 to 1.16 ± 0.33 in the region surrounding the septal deviation, showing that the nasal airway became more symmetric after virtual septoplasty.

CONCLUSION

This automated virtual septoplasty technique has the potential to greatly reduce the effort required to perform computational fluid dynamics (CFD) analysis of nasal airflow for NAO surgical planning. Future studies are needed to investigate if virtual surgery planning using this method is predictive of subjective symptoms in NAO patients after septoplasty.

Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry

Computational fluid dynamics (CFD) simulations of respiratory airflow have the potential to change the clinical assessment of regional airway function in health and disease, in pulmonary medicine and otolaryngology. For example, in diseases where multiple sites of airway obstruction occur, such as obstructive sleep apnea (OSA), CFD simulations can identify which sites of obstruction contribute most to airway resistance and may therefore be candidate sites for airway surgery. The main barrier to clinical uptake of respiratory CFD to date has been the difficulty in validating CFD results against a clinical gold standard. Invasive instrumentation of the upper airway to measure respiratory airflow velocity or pressure can disrupt the airflow and alter the subject's natural breathing patterns. Therefore, in this study, we instead propose phase contrast (PC) velocimetry magnetic resonance imaging (MRI) of inhaled hyperpolarized 129Xe gas as a non-invasive reference to which airflow velocities calculated via CFD can be compared. To that end, we performed subject-specific CFD simulations in airway models derived from 1H MRI, and using respiratory flowrate measurements acquired synchronously with MRI. Airflow velocity vectors calculated by CFD simulations were then qualitatively and quantitatively compared to velocity maps derived from PC velocimetry MRI of inhaled hyperpolarized 129Xe gas. The results show both techniques produce similar spatial distributions of high velocity regions in the anterior-posterior and foot-head directions, indicating good qualitative agreement. Statistically significant correlations and low Bland-Altman bias between the local velocity values produced by the two techniques indicates quantitative agreement. This preliminary in vivo comparison of respiratory airway CFD and PC MRI of hyperpolarized 129Xe gas demonstrates the feasibility of PC MRI as a technique to validate respiratory CFD and forms the basis for further comprehensive validation studies. This study is therefore a first step in the pathway towards clinical adoption of respiratory CFD.

Impact of Treatment for Nasal Cavity Disorders on Sleep Quality: Systematic Review and Meta-analysis

OBJECTIVE

To determine the impact of treatment for patients with nasal obstruction secondary to allergic rhinitis (AR) and nasal septal deviation (NSD) on sleep quality.

DATA SOURCES

Primary studies were identified though PubMed, Scopus, Cochrane Library, and Web of Science.

REVIEW METHODS

A systematic review was performed by querying databases for articles published through August 2020. Studies were included that reported on objective sleep parameters (apnea-hypopnea index) and sinonasal and sleep-specific patient-reported outcome measures: Rhinoconjunctivitis Quality of Life Questionnaire, Nasal Obstruction Symptom Evaluation, Epworth Sleepiness Scale (EpSS), and Pittsburgh Sleep Quality Index (PSQI).

RESULTS

The database search yielded 1414 unique articles, of which 28 AR and 7 NSD studies were utilized for meta-analysis. A total of 9037 patients (8515 with AR, 522 with NSD) were identified with a mean age of 35.0 years (35.3 for AR, 34.0 for NSD). Treatment for AR and NSD significantly improved subjective sleep quality. For AR, the EpSS mean difference was -1.5 (95% CI, -2.4 to -0.5; P = .002) and for the PSQI, -1.7 (95% CI, -2.1 to -1.2; P < .00001). For NSD, the EpSS mean difference was -3.2 (95% CI, -4.2 to -2.2; P < .00001) and for the PSQI, -3.4 (95% CI, -6.1 to -0.6; P = .02).

CONCLUSION

Subjective sleep quality significantly improved following treatment for AR and NSD. There were insufficient data to demonstrate that objective metrics of sleep quality similarly improved.

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.

The Virtual Nose: Assessment of Static Nasal Airway Obstruction Using Computational Simulations and 3D-Printed Models

Background: The use of virtual noses to predict the outcome of surgery is of increasing interests, particularly, as detailed and objective pre- and postoperative assessments of nasal airway obstruction (NAO) are difficult to perform. The objective of this article is to validate predictions using virtual noses against their experimentally measured counterpart in rigid 3D-printed models. Methods: Virtual nose models, with and without NAO, were reconstructed from patients' cone beam computed tomography scans, and used to evaluate airflow characteristics through computational fluid dynamics simulations. Prototypes of the reconstructed models were 3D printed and instrumented experimentally for pressure measurements. Results: Correlation between the numerical predictions and experimental measurements was shown. Analysis of the flow field indicated that the NAO in the nasal valve increases significantly the wall pressure, shear stress, and incremental nasal resistance behind the obstruction. Conclusions: Airflow predictions in static virtual noses correlate well with detailed experimental measurements on 3D-printed replicas of patient airways.

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.

Assessing the Clinical Value of Performing CT Scan before Rhinoplasty Surgery

Introduction

The endonasal mucosal or anatomic pathologies could lead to poor functional results and dissatisfaction after rhinoplasty. Although computed tomography (CT) scan has become an integral part of the diagnostic paradigm for patients with pathologies of the paranasal sinuses, the use of CT scan for preoperative evaluation of patients seeking rhinoplasty is up for debate. Our aim in this study was to compare the efficacy of CT scan in diagnosing nasal pathologies with other evaluating tools in patients undergoing rhinoplasty.

Design

In this randomized controlled trial study, 74 consecutive patients seeking cosmetic rhinoplasty referred to otorhinolaryngology clinic were randomly assigned into three groups based on the perioperative evaluation method: the CT group, the nasal endoscopy group, and the control group (anterior rhinoscopy only). Surgical planning was made according to perioperative findings, and the identified endonasal pathologies were corrected during the surgery. The functional and aesthetic outcomes of the rhinoplasty were assessed by Nasal Obstruction Symptom Evaluation (NOSE), Rhinoplasty Outcome Evaluation (ROE), and the Visual Analogue Scale (VAS) tools before surgery and at 12-month follow-up.

Results

All outcome measures improved significantly in either group toward one year after rhinoplasty (all with p value <0.05). Subjects in the CT group demonstrated greater improvement in the NOSE, VAS, and ROE compared to other two groups (NOSE: p value = 0.17; VAS: p value = 0.024; ROE: p value = 0.042).

Conclusions

According to our study, perioperative CT is associated with greater patients' satisfaction and quality of life after rhinoplasty compared to either nasal endoscopy or anterior rhinoscopy. A preoperative CT scan may improve the outcomes of rhinoplasty.

Can computational fluid dynamic models help us in the treatment of chronic rhinosinusitis

PURPOSE OF REVIEW

The aim of this study was to review the recent literature (January 2017-July 2020) on computational fluid dynamics (CFD) studies relating to chronic rhinosinusitis (CRS), including airflow within the pre and postoperative sinonasal cavity, virtual surgery, topical drug and saline delivery (sprays, nebulizers and rinses) and olfaction.

RECENT FINDINGS

Novel CFD-specific parameters (heat flux and wall shear stress) are highly correlated with patient perception of nasal patency. Increased ostial size markedly improves sinus ventilation and drug delivery. New virtual surgery tools allow surgeons to optimize interventions. Sinus deposition of nasal sprays is more effective with smaller, low-inertia particles, outside of the range produced by many commercially available products. Saline irrigation effectiveness is improved using greater volume, with liquid entering sinuses via 'flooding' of ostia rather than direct jet entry.

SUMMARY

CFD has provided new insights into sinonasal airflow, air-conditioning function, the nasal cycle, novel measures of nasal patency and the impact of polyps and sinus surgery on olfaction. The deposition efficiency of topical medications on sinus mucosa can be markedly improved through parametric CFD experiments by optimising nasal spray particle size and velocity, nozzle angle and insertion location, while saline irrigation effectiveness can be optimized by modelling squeeze bottle volume and head position. More sophisticated CFD models (inhalation and exhalation, spray particle and saline irrigation) will increasingly provide translational benefits in the clinical management of CRS.

The Relationship Between Nasal Septal Deviation and Paranasal Pneumatization

OBJECTIVE

To investigate the impact of the presence and the severity of the nasal septal deviation (NSD) on the paranasal pneumatization.

METHODS

Initially, the deviated and contralateral sides was compared to evaluate the impact of the presence of NSD on pneumatization. Then, NSD classification groups were categorized according to the severity of deviation degree; 1: mild (<9°), 2: moderate (9°-15°), and 3: severe (>15°). Pneumatization of all paranasal sinuses, osteomeatal complex (OMC), frontoethmoid recess (FER) and variant structures were compared according to the NSD classification groups separately both for the deviated and the contralateral sides.

RESULTS

Although there was no statistically significant difference in pneumatization of the paranasal sinuses between the deviated and contralateral sides, a significant difference was observed in OMC and FER diameters. In the deviated side, there was statistically significant difference in ethmoid sinus volume, in FER and OMC diameters between NSD classification groups. In the contralateral side, FER and OMC diameters were found to be significantly different between group 1 and group 2 and between group 1 and group 3, respectively (P = 0.04 and 0.06, respectively). Both the presence and severity of the NSD did not statistically significant influence the pneumatization of variant structures, air cells and vital structures.

CONCLUSION

The severity of NSD effects the ethmoid sinus volume. The relationship of FER and OMC with NSD is evident, however this may not always be in a proportional pattern. The paranasal pneumatization did not affect Keros type, bone integrity of carotid canal and optic canal.

North American survey and systematic review on caudal Septoplasty

Background

Surgical correction of caudal septal deviation is a technically challenging step of functional rhinoplasty. Multiple surgical techniques have been described in the literature but comparing the efficacy of each in relieving obstruction presents a challenge. Outcome measures are necessary to adequately compare techniques. This study aims to describe the current caudal septoplasty techniques of Otolaryngologists and Facial plastic and reconstructive surgeons (FPRS), as well as their use of outcome measures, and to compare these practices with surgical trends described in the literature.

Methods

An online survey was sent to three Otolaryngology and FPRS associations in Canada and the United States. A systematic review was conducted on SCOPUS and PubMed to classify the caudal septoplasty techniques described in the literature and the outcome measurement tools used.

Results

Our survey identified that caudal septoplasty is more commonly performed by surgeons with an FPRS training background. The most common techniques were the swinging door technique (69.5%), extracorporeal septoplasy (46.7%), cartilage scoring (45.3%), and splinting with bone (25.4%). Despite using a vast array of surgical techniques, North American physicians rarely rely on standardized outcome assessment tools. Patient reported outcome measures (PROMs) are used almost twice as frequently in the literature as they are by surgeons in their clinical practice.

Conclusion

We recommend that future studies of caudal septoplasty include an assessment of both form and function using a validated PROM such as the Standardized Cosmesis and Health Nasal Outcomes Survey.

Narrowed Posterior Nasal Airway Limits Efficacy of Anterior Septoplasty

Background: Predicting symptomatic relief after septoplasty has been difficult. Minimal cross-sectional area (mCSA) measured by acoustic rhinometry and airflow resistance (R) measured by rhinomanometry have been used to select surgical candidates with mixed success. An important assumption is that mCSA and resistance are tightly coupled, but studies have reported weak or no correlation. Recently, we proposed the Bernoulli Obstruction Theory as an explanation, where tight coupling between mCSA and R is only predicted below a critical mCSA (A_crit). Methods: The nasal airway and septum of 10 healthy subjects were reconstructed from computed tomography scans. Simulated anterior septal deviations of increasing severity were created. Computational fluid dynamics simulations were performed to quantify mCSA, resistance, and flow in the healthy septum model and four simulated septal deviation models for each subject (total of 50 models). Results: A tighter coupling between mCSA and resistance was found below A_crit, estimated to be 0.20 cm² (a very severe deviation). Above A_crit, enlarging the mCSA had a smaller effect in patients with narrower cross-sectional area in the postvalve region (CSA_PV). Conclusions: Two patterns of flow increase are expected with septoplasty. Below A_crit, enlarging mCSA predictably increases flow. Above A_crit, the effect size of increasing mCSA depends on CSA_PV. Unrecognized small CSA_PV may explain persistent sensation of nasal obstruction after septoplasty. Our data suggest that inferior turbinate reduction ipsilateral to a septal deviation may amplify airflow benefits after septoplasty in patients with a narrow CSA_PV.

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.

Virtual septoplasty: a method to predict surgical outcomes for patients with nasal airway obstruction

PURPOSE

A deviated nasal septum is the most common etiology for nasal airway obstruction (NAO), and septoplasty is the most common surgical procedure performed by ear-nose-throat surgeons in adults. However, quantitative criteria are rarely adopted to select patients for surgery, which may explain why up to 50% of patients report persistent or recurrent symptoms of nasal obstruction postoperatively. This study reports a systematic virtual surgery method to identify patients who may benefit from septoplasty.

METHODS

One patient with symptoms of NAO due to a septal deviation was selected to illustrate the virtual surgery concept. Virtual septoplasty was implemented in three steps: (1) determining if septal geometry is abnormal preoperatively, (2) virtually correcting the deviation while preserving the anatomical shape of the septum, and (3) estimating the post-surgical improvement in airflow using computational fluid dynamics. Anatomical and functional changes predicted by the virtual surgery method were compared to a standard septoplasty performed independently from the computational analysis.

RESULTS

A benchmark healthy nasal septum geometry was obtained by averaging the septum dimensions of 47 healthy individuals. A comparison of the nasal septum geometry in the NAO patient with the benchmark geometry identified the precise locations where septal deviation and thickness exceeded the healthy range. Good agreement was found between the virtual surgery predictions and the actual surgical outcomes for both airspace minimal cross-sectional area (0.05 cm² pre-surgery, 0.54 cm² virtual surgery, 0.50 cm² actual surgery) and nasal resistance (0.91 Pa.s/ml pre-surgery, 0.08 Pa.s/ml virtual surgery, 0.08 Pa.s/ml actual surgery).

CONCLUSIONS

Previous virtual surgery methods for NAO were based on manual edits and subjective criteria. The virtual septoplasty method proposed in this study is objective and has the potential to be fully automated. Future implementation of this method in virtual surgery planning software has the potential to improve septoplasty outcomes.

Cartilage Trap-Door Flap Technique for Correction of High Nasal Septum Deflection

OBJECTIVE

To introduce a novel cartilage trap-door flap technique in endonasal septoplasty to correct high dorsal deviation of the cartilaginous septum, and confirm its effectiveness.

DESIGN

Prospective observational study.

SETTING

Medical center.

METHODS

46 patients who had underwent septoplasty using the cartilage island flap technique to correct the high dorsal deviation from November 2014 to November 2015. The subjective symptoms were measured using the Nasal Obstruction Symptom Evaluation scale. The objective evaluations of the surgical results were analyzed using acoustic rhinometry. Post-operative status of the nasal septum was estimated by nasal endoscopic examination.

RESULTS

Among 46 patients, 32 cases (69.57%) were "complete correction", 14cases (30.43%) were "improved" with residual deviation and there was not "no-change" or "even worse" case based on endoscopic examination. Minimal cross-sectional area in convex side of nasal cavity was significantly changed from 0.22cm to 0.56cm after the surgery, and nasal volume in narrower side of nasal cavity was significantly changed from 2.44mL to 6.22 mL. The patients' nasal obstruction symptoms significantly reduced from 10.43 before the surgery to 1.45 after the surgery. During the follow-up period, the authors have not experienced any obvious complications such as saddle nose, septal perforation, and bleeding.

CONCLUSION

The proposed cartilage trap-door flap technique provides easy and effective results for dorsal deviations of the cartilaginous septum in selected cases without significant complications.

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.

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.

Computational Fluid Dynamics to Evaluate the Effectiveness of Inferior Turbinate Reduction Techniques to Improve Nasal Airflow

Importance

Inferior turbinate reduction (ITR) is a commonly performed procedure for the treatment of nasal obstruction. Which portion of the inferior turbinates should be surgically addressed to improve nasal airflow has yet to be determined.

Objective

To use computational fluid dynamics (CFD) analysis to evaluate the airflow changes after reduction along different portions of the inferior turbinate.

Design, Setting, and Participants

Computed tomographic scans of 5 patients were selected. Seven CFD models were created for each patient: 1 unaltered and 6 various ITRs, including 3 one-third ITRs (anterior, middle, and posterior one-third); 2 two-thirds ITRs (anterior and posterior two-thirds); and 1 full-length ITR model. Total airflow rate and nasal resistance was obtained through CFD analysis, and regression analysis was performed on the increased nasal volume, locations, and nasal resistance for all 5 patients.

Main Outcomes and Measures

Total airflow rate and nasal resistance was obtained through CFD analysis, and regression analysis was performed on the increased nasal volume, locations, and nasal resistance for all 5 patients.

Results

Full ITR over the whole length was consistently most effective to improve nasal airflow and resistance for all 5 patients (2 men and 3 women), adjusted for the volume. Regression analysis showed a strong linear (R2≥0.79) relationship between nasal volume changes and nasal airflow. However, the most effective location of partial turbinate reduction was not consistent among patients. Surprisingly, for some patients, posterior ITRs were more effective than anterior ITRs. The site of most effective partial ITR differed from 1 side to the other even in the same individual.

Conclusions and Relevance

The effectiveness of partial ITR and target location likely depends on individual patient anatomy. The fact that full ITRs were consistently most effective and the linear regression between flow and nasal volume changes may indicate that the entire length of the IT has a functional impact on nasal airflow and resistance.

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.

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.

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non-rigid registration of dynamic and static MRI

Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all. Many common airway pathologies, such as obstructive sleep apnea (OSA) and tracheomalacia, involve large movements of the structures surrounding the airway, such as the tongue and soft palate. Airway wall motion may be due to many factors including neuromuscular motion, internal aerodynamic forces, and external forces such as gravity. Therefore, to realistically model these airway diseases, a method is required to derive the airway wall motion, whatever the cause, and apply it as a boundary condition to CFD simulations. This paper presents and validates a novel method of capturing in vivo motion of airway walls from magnetic resonance images with high spatiotemporal resolution, through a novel combination of non-rigid image, surface, and surface-normal-vector registration. Coupled with image-synchronous pneumotachography, this technique provides the necessary boundary conditions for dynamic CFD simulations of breathing, allowing the effect of the airway's complex motion to be calculated for the first time, in both normal subjects and those with conditions such as OSA.

Sensitivity of nasal airflow variables computed via computational fluid dynamics to the computed tomography segmentation threshold

Computational fluid dynamics (CFD) allows quantitative assessment of transport phenomena in the human nasal cavity, including heat exchange, moisture transport, odorant uptake in the olfactory cleft, and regional delivery of pharmaceutical aerosols. The first step when applying CFD to investigate nasal airflow is to create a 3-dimensional reconstruction of the nasal anatomy from computed tomography (CT) scans or magnetic resonance images (MRI). However, a method to identify the exact location of the air-tissue boundary from CT scans or MRI is currently lacking. This introduces some uncertainty in the nasal cavity geometry. The radiodensity threshold for segmentation of the nasal airways has received little attention in the CFD literature. The goal of this study is to quantify how uncertainty in the segmentation threshold impacts CFD simulations of transport phenomena in the human nasal cavity. Three patients with nasal airway obstruction were included in the analysis. Pre-surgery CT scans were obtained after mucosal decongestion with oxymetazoline. For each patient, the nasal anatomy was reconstructed using three different thresholds in Hounsfield units (-800HU, -550HU, and -300HU). Our results demonstrate that some CFD variables (pressure drop, flowrate, airflow resistance) and anatomic variables (airspace cross-sectional area and volume) are strongly dependent on the segmentation threshold, while other CFD variables (intranasal flow distribution, surface area) are less sensitive to the segmentation threshold. These findings suggest that identification of an optimal threshold for segmentation of the nasal airway from CT scans will be important for good agreement between in vivo measurements and patient-specific CFD simulations of transport phenomena in the nasal cavity, particularly for processes sensitive to the transnasal pressure drop. We recommend that future CFD studies should always report the segmentation threshold used to reconstruct the nasal anatomy.

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.

Effect of Nasal Valve Shape on Downstream Volume, Airflow, and Pressure Drop: Importance of the Nasal Valve Revisited

OBJECTIVES

The relative importance of the nasal valve relative to the remainder of the nasal airway remains unknown. The goal of this article was to objectively measure the shape of the nasal inlet and its effect on downstream airflow and nasal cavity volume using a physical model and a physiologic flow model.

METHODS

A patient who had isolated nasal valve surgery and had pre- and postoperative computed tomography scans available for analysis was studied. Nasal inlet shape measurements, computational fluid dynamics, and nasal volume analysis were performed using the computed tomography data. In addition, a physical model was used to determine the effect of nasal obstruction on downstream soft tissue.

RESULTS

The postoperative shape of the nasal inlet was improved in terms of length and degree of tortuosity. Whereas the operated-on region at the nasal inlet showed an only 25% increase in cross-sectional area postoperatively, downstream nonoperated sites in the nasal cavity revealed increases in area ranging from 33% to 51%. Computational fluid dynamics analysis showed that airway resistance decreased by 42%, and pressure drop was reduced by 43%. Intraluminal mucosal expansion was found with nasal obstruction in the physical model.

CONCLUSION

By decreasing the degree of bending and length at the nasal valve, inspiratory downstream nonoperated sites of the nasal cavity showed improvement in volume and airflow, suggesting that the nasal valve could play an oversized role in modulating the aerodynamics of the airway. This was confirmed with the physical model of nasal obstruction on downstream mucosa.

Functional and Aesthetic Factors Associated with Revision of Rhinoplasty

Background

Surgical revision rate of rhinoplasty is from 5% to 15% in literature. The aims of our study were to define the rate and the predictive factors for surgical revision of rhinoplasty.

Methods

We have realized a single-center case/control study including 62 patients who underwent surgical revision among 732 patients who underwent closed rhinoplasty between 2005 and 2015. Data of each rhinoplasty were collected from medical records and photographs. Statistical analyses were used.

Results

The surgical revision rate was 8.6%. After multivariate analysis, 4 factors were statistically significant and independently associated with surgical revision: "preexisting respiratory functional disorder" [odds ratio OR = 3.30; 95% CI (1.47-7.76); P = 0.004], "wide nasal bone and side walls" [OR = 3.94; 95% CI (1.49-11.25); P = 0.007], "deviated nasal bone and side walls" [OR = 2.68; 95% CI [1.14-6.58]; P = 0.02] and the use of camouflage grafts [OR = 0.26; 95% CI [0.07-0.89]; P = 0.04].

Conclusions

Closed rhinoplasties have similar revision rate to open techniques. Revision surgeries are justified by functional or aesthetic disorders. The interests of this study are to better inform patients and to adapt operative management. We provide here some recommendations with focus on the keys to successful rhinoplasty surgery.

Diagnostic Algorithm for Evaluating Nasal Airway Obstruction

Nasal obstruction is a common symptom and can have a large impact on patient quality of life. There are numerous causes, including anatomic, congenital, inflammatory, infectious, neoplastic, toxic, and systemic. An algorithmic approach can aid in ensuring all pertinent patient information is incorporated into the final diagnosis and treatment plan. Key components include a thorough history, physical examination including modified Cottle and Cottle maneuver, patient-reported outcome measures and/or quality of life questionnaires, examination with and without decongestion, and nasal endoscopy. The resultant information can then be effectively used to narrow the differential and guide the next steps in management.

A prospective cohort study assessing the clinical utility of the Cottle maneuver in nasal septal surgery

BACKGROUND

A nasal septal deviation can have a significant detrimental effect on a patient's quality of life. Nasal valve collapse (NVC) often co-exists with a septal deviation. The Cottle maneuver is one of the most common methods to diagnose NVC; however, no study has assessed the efficacy of this physical exam finding. This study tests the hypothesis that patients with nasal obstruction due to a septal deviation with a negative pre-operative Cottle maneuver will demonstrate a greater improvement in their Nasal Obstruction Symptom Evaluation (NOSE) score, compared to patients who demonstrate a positive pre-operative Cottle maneuver, when assessed at 12 months following a septoplasty with turbinate diathermy.

METHODS

This was a prospective Cohort Study. The population was 141 patients with nasal obstruction due to a septal deviation with or without nasal valve collapse, excluding patients with bilateral complete nasal valve collapse. Patients were placed in cohorts according to the results of the Cottle maneuver (positive or negative). A NOSE questionnaire was administered at baseline and 12-months after a septoplasty with turbinate diathermy. Non-adjusted NOSE scores were used (score out of 20). An ANOVA was used to compare if there was a difference in outcomes between patient cohorts.

RESULTS

One hundred and forty-one patients completed 12-month follow-up with 71.5% of patients demonstrating a positive Cottle maneuver at baseline. The mean (95% C.I.) difference in NOSE score at 12 months between patients with a positive Cottle versus a negative Cottle was 0.18 (- 1.6 to 1.92; p = 0.38).

CONCLUSION

In a univariate, single surgeon study, a positive Cottle Maneuver does not appear to influence outcomes in the described patient population compared to those with a negative Cottle Maneuver when undergoing a septoplasty.

Treatment Paradigm for Nasal Airway Obstruction

Nasal airway obstruction (NAO) is a common otolaryngic complaint with many potential causes, frequently structural or inflammatory in nature. Patients typically have multiple coexisting factors leading to symptoms. Good patient outcomes require careful preoperative evaluation, including nasal endoscopy, to accurately identify sources of obstruction and tailor intervention appropriately. Common structural causes of NAO include inferior turbinate hypertrophy, nasal septal deviation, and narrowing or collapse of the internal or external nasal valves. The internal nasal valve has the narrowest cross-sectional area within the nasal airway and is thus most sensitive to changes in dimension due to anatomic variation or surgical intervention.

Measuring Nasal Obstruction Outcomes

Methods of measuring nasal obstruction outcomes include both objective anatomic and physiologic measurements, as well as subjective patient-reported measures. Anatomic measurements include acoustic rhinometry, imaging studies, and clinician-derived examination findings. Physiologic measures include rhinomanometry, nasal peak inspiratory flow, and computational fluid dynamics. Patient-reported outcome measures (PROMs) are self-reported assessments of disease-specific quality-of-life outcomes. Several studies attempted correlation of these outcome measures; however, few show strong correlation. Expert opinion favors determining successful surgical outcomes using PROMs. This review provides a summary of current nasal obstruction outcome measures.

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.