Computational fluid dynamics as surgical planning tool: a pilot study on middle turbinate resection

Oxymetazoline as a predictor of turbinate reduction surgery outcomes: Objective support from a prospective, single-blinded, computational fluid dynamics study

BACKGROUND

A patient's subjective response to topical nasal decongestant is often used to screen for turbinate reduction surgery suitability. However, this anecdotal strategy has not been objectively and quantitatively evaluated.

METHODS

Prospective, longitudinal, and single-blinded cohort study employing computational fluid dynamic modeling based on computed tomography scans at baseline, 30 min postoxymetazoline, and 2 months postsurgery on 11 patients with chronic turbinate hypertrophy.

RESULTS

Nasal obstruction symptom evaluation (NOSE) and visual analogue scale (VAS) obstruction scores significantly improved from baseline to postoxymetazoline and again to postsurgery (NOSE: 71.82 ± 14.19 to 42.27 ± 25.26 to 22.27 ± 21.04; VAS: 6.09 ± 2.41 to 4.14 ± 2.20 to 2.08 ± 1.56; each interaction p < 0.05), with significant correlation between the latter two states (r∼0.37-0.69, p < 0.05). Oxymetazoline had a broader anatomical impact throughout inferior and middle turbinates than surgery (many p < 0.05); however, the improvement in regional airflow is similar (most p > 0.05) and predominantly surrounding the inferior turbinate. Strong postoxymetazoline to postsurgery correlations were observed in decreased nasal resistance (r = 0.79, p < 0.05), increased regional airflow rates (r = -0.47 to -0.55, p < 0.05) and regional air/mucosa shear force and heat flux (r = 0.43 to 0.58, p < 0.05); however, only increasing peak heat flux significantly correlated to symptom score improvement (NOSE: r = 0.48, p < 0.05).

CONCLUSION

We present the first objective evidence that the "topical decongestant test" can help predict turbinate reduction surgery outcomes. The predictive effect is driven by similar improvementin regional airflow that leading to improved air/mucosa stimulations (peak heat flux) rather than through reduced nasal resistance.

Optimized gravity-driven intranasal drop administration delivers significant doses to the ostiomeatal complex and maxillary sinus

Chronic and allergic rhinosinusitis impacts approximately 12% of the global population. Challenges in rhinosinusitis treatment include paranasal sinus inaccessibility and variability in delivery efficiency among individuals. This study addresses these challenges of drug delivery by developing a high-efficiency, low-variability protocol for nasal drop delivery to the ostiomeatal complex (OMC) and maxillary sinus. Patient-specific nasal casts were dissected to reveal the configurations of conchae and meatus, providing insights into anatomical features amendable for sinus delivery. Fluorescent dye-enhanced videos visualized the dynamic liquid translocation in transparent nasal casts, allowing real-time assessment and quick adjustment to delivery parameters. Dosimetry to the OMC and maxillary sinus were quantified as drop count and mass using a precision scale. Key delivery factors, including the device type, formulation, and head-chin orientation, were systematically investigated in a cohort of ten nasal casts. Results show that both the squeeze bottle and soft-mist nasal pump yielded notably low doses to the OMC with high variability, and no dose from these two devices was detected within the maxillary sinuses. In contrast, the proposed approach, which included a curved nozzle surpassing the nasal valve and leveraged gravity-driven liquid translocation along the lateral nasal wall, delivered significant doses to the OMC and maxillary sinus. Iterative experimentations identified the optimal head tilt to be 40° and chin tilt to be° from the lateral recumbent position. Statistical analyses established the drop count required for effective OMC/sinus delivery. The proposed delivery protocol holds the potential to enhance chronic rhinosinusitis treatment outcomes with low variability. The dual role of nasal anatomy in posing challenges and offering opportunities highlights the need for future investigations using diverse formulations in a larger cohort of nasal models.

Effect of preservation versus resection of turbinate on olfactory function in endoscopic trans-nasal trans-sphenoidal pituitary surgery: a systematic review and meta-analysis

BACKGROUND

Utilizing endoscopes in surgery offers advantages and concerns, including potential nasal function impacts. Hyposmia following Transseptal Transsphenoidal hypophysectomy ranges from 0% to 2.2%. Debates persist about managing the M.T. in endoscopic sinus surgery due to its impact on nasal function. While preservation is recommended for sinonasal health, debates continue, as certain cases require resection. Our meta-analysis aims to compare turbinate resection and preservation effects on olfactory function.

METHODS

We searched five electronic databases to collect all relevant studies. Records were screened for eligibility. Data were extracted from the included studies independently. Our continuous outcomes were pooled as standardized mean difference with 95% CI. Statistical analyses was done by RevMan.

RESULTS

Our meta-analysis included four studies involving 235 patients (81 males). Evaluating changes in olfaction scores, two one-month studies (82 patients) revealed no significant difference between preservation and resection groups (Std.MD = 0.05[-0.39, 0.50], p = 0.81). For three-month assessments (146 patients), SNOT tests indicated no significant difference (Std.MD = 0.21, 95% CI[-0.11, 0.54], p = 0.20). Two studies used other tests on 70 patients at three months, yielding no significant difference (Std.MD = 0.13, 95% CI [-0.35, 0.62], p = 0.59). Two six-month studies (72 patients) similarly found no significant difference (Std.MD = 0.09, 95% CI [-0.39, 0.56], p = 0.72).

CONCLUSION

Our meta-analysis involving 235 patients examined olfaction score changes over various time frames in trans-nasal trans-sphenoidal pituitary surgeries. No significant differences were observed between turbinate preservation and resection groups at one month, three months, or six months post-surgery.

How Does Oxymetazoline Change Nasal Aerodynamics and Symptomatology in Patients with Turbinate Hypertrophy?

OBJECTIVES

Oxymetazoline relieves nasal obstructive symptoms via vasoconstriction, however, the changes in nasal structures and aerodynamics that impact symptoms the most remain unclear.

METHODS

This prospective, longitudinal, and single blinded cohort study applied Computational Fluid Dynamic (CFD) modeling based on CT scans at baseline and post-oxymetazoline on 13 consecutive patients with chronic nasal obstruction secondary to inferior turbinate hypertrophy from a tertiary medical center. To account for placebo effect, a sham saline spray was administered with subject blindfolded prior to oxymetazoline, with 30 min rest in between. Nasal Obstruction Symptom Evaluation (NOSE) and unilateral Visual Analogue Scale (VAS) scores of nasal obstructions were collected at baseline, after sham, and 30 min after oxymetazoline.

RESULTS

Both VAS and NOSE scores significantly improved from baseline to post-oxymetazoline (NOSE: 62.3 ± 12.4 to 31.5 ± 22.5, p < 0.01; VAS: 5.27 ± 2.63 to 3.85 ± 2.59, p < 0.05), but not significantly from baseline to post-sham. The anatomical effects of oxymetazoline were observed broadly throughout the entire length of the inferior and middle turbinates (p < 0.05). Among many variables that changed significantly post-oxymetazoline, only decreased nasal resistance (spearman r = 0.4, p < 0.05), increased regional flow rates (r = -0.3 to -0.5, p < 0.05) and mucosal cooling heat flux (r = -0.42, p < 0.01) in the inferior but not middle turbinate regions, and nasal valve Wall Shear Stress (WSS r = -0.43, p < 0.05) strongly correlated with symptom improvement.

CONCLUSION

Oxymetazoline broadly affects the inferior and middle turbinates, however, symptomatic improvement appears to be driven more by global nasal resistance and regional increases in airflow rate, mucosal cooling, and WSS, especially near the head of the inferior turbinate.

LEVEL OF EVIDENCE

3: Well-designed, prospective, single blinded cohort trial. Laryngoscope, 134:1100-1106, 2024.

Numerical and experimental analysis of pollen inhalation exposure in nasal airways following various middle turbinectomy

BACKGROUND

Middle turbinectomy (MT) has always been controversial. MT significantly alters the anatomy and redistributes the inhaled air. The current study is designed to quantify the effect of MT with varying resection volumes on airflow and associated pollen inhalation exposure characteristics in the nasal airways.

METHODS

Six realistic models following bilateral comprehensive Functional Endoscopic Sinus Surgery (FESS) deriving from CT images were constructed and their corresponding post-MT models with four types of MT procedures were virtually conducted. Inhalation exposure to pollen particles was simulated by the Computational Fluid-Particle Dynamics (CFPD) approach and validated through in vitro experiments.

RESULTS

Following the excision of the middle turbinate, a significant escalation in airflow was observed within the upper-middle region of the nasal cavities. Pollen deposition was observed to be more prominent in the nasal septum, laryngopharynx, and maxillary sinus, varying with the types of MT procedures. Notably, particles with diameters smaller than 50 μm exhibited two distinct "high peaks" and three "small peaks" within the nasal airways.

CONCLUSION

MT resulted in increased airflow volume within the upper-middle region of the nasal cavities. Following MT, notable shifts in pollen particle deposition hot spots were observed, transitioning from the nasal vestibule, nasal septum, and middle meatus to the nasal septum and laryngopharynx. These findings are anticipated to contribute valuable perspectives on pollen inhalation exposure risk assessments following diverse MT surgical interventions.

The Effect of Segmentation Threshold on Computational Fluid Dynamic Analysis of Nasal Airflow

BACKGROUND

The objective analysis of nasal airflow stands to benefit greatly from the adoption of computational fluid dynamic (CFD) methodologies. In this emerging field, no standards currently exist in regard to the ideal modeling parameters of the nasal airway. Such standards will be necessary for this tool to become clinically relevant.

METHODS

Human nasal airways were modeled from a healthy control, segmented, and analyzed with an in-house immersed boundary method. The segmentation Hounsfield unit (HU) threshold was varied to measure its effect in relation to airflow velocity magnitude and pressure change.

FINDINGS

Surface area and volume have a linear relationship to HU threshold, whereas CFD variables had a more complex relationship.

INTERPRETATION

The HU threshold should be included in nasal airflow CFD analysis. Future work is required to determine the optimal segmentation threshold.

Correlation analysis of flow parameters in the olfactory cleft and olfactory function

The olfaction is related to flow in the olfactory cleft. However, There is a lack of studies on the relationship between flow characteristics of the olfactory cleft and olfactory function. In this study, the anatomical structure of the olfactory cleft was reconstructed in three dimensions using the raw data obtained from the CT scans of sinuses of 32 enrolled volunteers. The Sniffin' Sticks test was used to examine the olfaction. We investigated the correlation between airflow parameters and olfactory function of the olfactory cleft in healthy adults by the computational fluid dynamics method. We found that three parameters, airflow, airflow velocity, and airflow ratio, were highly positively correlated with olfactory function. The mean pressure was not correlated with the olfactory function. Furthermore, there is the strongest correlation between air flow through the olfactory cleft and olfactory function. The correlation between the mean velocity in the anterior olfactory cleft region and olfaction was relatively poor, while the airflow velocity at the posterior olfactory cleft region was enhanced gradually. The correlation between the airflow ratio and olfaction was optimal in the initial position of superior turbinate. The flow parameters in the posterior olfactory cleft area were more stable.

Olfactory Outcomes After Middle Turbinate Resection in Endoscopic Transsphenoidal Surgery: A Prospective Randomized Study

OBJECTIVE

Endoscopic endonasal transsphenoidal surgery is safe and effective for sellar and parasellar tumor removal. Partial middle turbinate (MT) resection is sometimes performed to optimize the surgical field and facilitate postoperative care. Disturbances in olfaction are concerning because of the lack of randomized studies in this field.

STUDY DESIGN

Prospective randomized trial.

SETTING

Single academic medical center.

METHODS

We resected the lower halves of bilateral MTs in the resected group and laterally fractured bilateral MTs in the preserved group. Olfactory outcomes and sinonasal conditions were assessed by using the validated Taiwan Smell Identification Test and Lund-Kennedy Endoscopy Score, respectively. Forty-nine patients were enrolled in the final analysis, of whom 23 underwent partial MT resection.

RESULTS

The average Taiwan Smell Identification Test result was 36.9 one month after surgery, with a significant change of -4.4 ± 3.1 (mean ± SD; P < .01) from baseline. The impact was not significant at 3 months (-2.1 ± 2.6, P = .13) or 6 months (0.3 ± 2.0, P = .79). Between the MT resection and preservation groups, there were no significant differences at postoperative 1 month (P = .60), 3 months (P = .86), and 6 months (P > .99). Lund-Kennedy Endoscopy Score was still higher at 3 months (P = .006) after surgery but returned to the preoperative level at 6 months (P = .63).

CONCLUSIONS

Endoscopic endonasal transsphenoidal surgery may affect olfaction at 1 month after surgery, and olfactory function is expected to return after 3 months. Partial MT resection did not result in additional olfactory loss. It is safe to perform partial MT resection during surgery without compromising the olfactory outcomes.

Septoplasty Effect on the Enhancement of Airflow Distribution and Particle Deposition in Nasal Cavity: A Numerical Study

The surgery outcomes after fixing nasal airway obstruction (NAO) are sometimes not satisfactory in improving ventilations of airflow. A case study is presented in this paper with computational fluid dynamics applied to determine the key factors for successful septoplasty plans for a patient with a deviated nasal septum. Specifically, airflow, as well as particle transport and deposition were predicted in a pre-surgery nasal cavity model reconstructed from patient-specific Computer Tomography (CT) images and two post-surgery nasal cavity models (i.e., VS1 and VS2) with different virtual surgery plans A and B. Plan A corrected the deviated septal cartilage, the perpendicular plate of the ethmoid bone, vomer, and nasal crest of the maxilla. Plan B further corrected the obstruction in the nasal vestibule and caudal nasal septal deviation based on Plan A. Simulations were performed in the three nose-to-throat airway models to compare the airflow velocity distributions and local particle depositions. Numerical results indicate that the VS2 model has a better improvement in airflow allocation between the two sides than the VS1 model. In addition, the deposition fractions in the VS2 model are lower than that in both the original and VS1 models, up to 25.32%. The better surgical plan (i.e., Plan B) reduces the particle deposition on the convex side, but slightly increases the deposition on the concave side. However, the overall deposition in the nasal cavity is reduced.

Evidence of Nasal Cooling and Sensory Impairments Driving Patient Symptoms With Septal Deviation

OBJECTIVES/HYPOTHESIS

About 260,000 septoplasties are performed annually in the US to address nasal septal deviation (NSD). Yet, we do not consistently understand what aspects of NSD result in symptoms.

STUDY DESIGN

Blinded cohort study.

METHODS

Two fellowship-trained surgeons blindly reviewed computerized tomography (CTs) of 10 confirmed NSD patients mixed with 36 healthy controls. All patients were correctly identified, however, 24/36 controls were falsely identified by both surgeons as patients (33.3% specificity), which were grouped as asymptomatic NSD (aNSD), while the remaining controls as non-NSD (healthy). Acoustic rhinometry, rhinomanometry, individual CT-based computational fluid dynamics and nasal sensory testing were applied to address the puzzling questions of why these aNSD had no symptoms and, more fundamentally, what caused symptoms in sNSD patients.

RESULTS

aNSD reported no nasal symptoms - Nasal Obstruction Symptom Evaluation score (sNSD: 60.50 ± 13.00; aNSD: 5.20 ± 5.41; non-NSD: 6.66 ± 7.17, P < .05); 22-item Sino-Nasal Outcome Test score (sNSD: 32.60 ± 14.13; aNSD: 10.04 ± 10.10; non-NSD: 9.08 ± 12.42, P < .001). No significant differences in measured nasal resistance, minimum cross-sectional area (MCA), degree of septal deviation, and nasal airflow distributions were found between sNSD and aNSD groups. Only three variables differentiate sNSD versus aNSD: anterior averaged heat flux on deviated side, inferior turbinate peak heat flux on non-deviated side, and nasal cool sensitivity measured by menthol lateralization threshold, with no significant differences among these variables found between the two healthy groups (aNSD vs. non-NSD). These variables by themselves or combined can differentiate sNSD from controls with higher specificity than the physicians (ROC area under the curve = 0.84 with 70% sensitivity and 91.6% specificity).

CONCLUSIONS

This study sheds light on the potential mechanisms of NSD symptomatology: distorted nasal cooling due to NSD exacerbated by poorer nasal mucosal sensitivity. It further supports our previous hypothesis that nasal obstruction complaints do not result directly from obstruction, rather from the capacity of our nose to subjectively sense airflow cooling.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:509-517, 2022.

Use of computational fluid dynamics (CFD) to model observed nasal nitric oxide levels in human subjects

BACKGROUND

Upper airway nitric oxide (NO) is physiologically important in airway regulation and defense, and nasal NO (nNO) levels typically exceed those in exhaled breath (fractional exhaled NO [FeNO]). Elevated concentrations of NO sampled from the nose, in turn, reflect even higher concentrations in the paranasal sinuses, suggesting a "reservoir" role for the latter. However, the dynamics of NO flux within the sinonasal compartment are poorly understood.

METHODS

Data from 10 human subjects who had previously undergone both real-time nNO sampling and computed tomography (CT) scanning of the sinuses were analyzed using computational fluid dynamics (CFD) methods. Modeled and observed nNO values during the initial 2-s transient ("spike") during nasal exhalation were then compared.

RESULTS

Examining the initial 2-s transient spike for each subject (as well as the pooled group), there was a statistically significant correlation between modeled and observed nNO levels, with r values ranging from 0.43 to 0.89 (p values ranging from <0.05 to <0.0001). Model performance varied between subjects, with weaker correlations evident in those with high background (FeNO) levels. In addition, the CFD simulation suggests that ethmoid sinuses (>60%) and diffusion process (>54%) contributed most to total nasal NO emissions.

CONCLUSION

Analysis of this dataset confirms that CFD is a valuable modeling tool for nNO dynamics, and highlights the importance of the ethmoid sinuses, as well as the role of diffusion as an initiating step in sinonasal NO flux. Future model iterations may apply more generally if baseline FeNO is taken into account.

Evaluation of nasal function after endoscopic endonasal surgery for pituitary adenoma: a computational fluid dynamics study

OBJECTIVE

To analyze the effect of different endoscopic endonasal approaches (EEAs) on nasal airflow and heating and humidification in patients with pituitary adenoma (PA) by computational fluid dynamics (CFD).

METHODS

A three-dimensional pre-surgical model (Pre) of the nasal cavity and 6 that were post-EEA surgery were created from computed tomography scans as follows: small posterior septectomy (0.5 cm, sPS), middle posterior septectomy (1.5 cm, mPS), large posterior septectomy (2.5 cm, lPS), and sPS with middle turbinate resection (sPS-MTR), mPS-MTR, and lPS-MTR. Simulations were performed by CFD to compare the changes in different models.

RESULTS

The temperature in the nasal vestibule rose more rapidly than in other parts of the nasal cavities in all models. There were no apparent differences in temperature and humidity among the models in sections anterior to the middle turbinate head (C6 section). MTR significantly influenced airflow distribution between the bilateral nasal cavities and the different parts of the nasal cavity, while changes in temperature and humidity in each section were mainly affected by MTR. The temperature and humidity of the choana and nasopharynx of each postoperative model were significantly different from those of the preoperative model and the change in values significantly correlated with the surface-to-volume ratio (SVR) of the airway.

CONCLUSIONS

Changes due to the different nasal structures caused different effects on nasal function following the use of EEA surgery for the treatment of PA. CFD provided a new approach to assess nasal function, promising to provide patients with individualized preoperative functional assessment and surgical planning.

Computational Fluid Dynamic Modeling Reveals Nonlinear Airway Stress during Trachea Development

Normative trachea dimensions and aerodynamic information during development was collected to establish clinical benchmarks and showed that airway development seems to outpace respiratory demands. Infants and toddlers' trachea exhibit higher aerodynamic stress that significantly decreases by teenage years. This implies large airway pathology in younger children may have a more substantial clinical impact.

Inhalation and deposition of spherical and pollen particles after middle turbinate resection in a human nasal cavity

Middle turbinate resection significantly alters the anatomy and redistributes the inhaled air. The superior half of the main nasal cavity is opened up, increasing accessibility to the region. This is expected to increase inhalation dosimetry to the region during exposure to airborne particles. This study investigated the influence of middle turbinate resection on the deposition of inhaled pollutants that cover spherical and non-spherical particles (e.g. pollen). A computational model of the nasal cavity from CT scans, and its corresponding post-operative model with virtual surgery performed was created. Two constant flow rates of 5 L/min, and 15 L/min were simulated under a laminar flow field. Inhaled particles including pollen (non-spherical), and a spherical particle with reference density of 1000 kg/m³ were introduced in the surrounding atmosphere. The effect of surgery was most prominent in the less patent cavity side, since the change in anatomy was proportionally greater relative to the original airway space. The left cavity produced an increase in particle deposition at a flow rate of 15 L/min. The main particle deposition mechanisms were inertial impaction, and to a lesser degree gravitational sedimentation. The results are expected to provide insight into inhalation efficiency of different aerosol types, and the likelihood of deposition in different nasal cavity surfaces.

Computational modeling of nasal nitric oxide flux from the paranasal sinuses: Validation against human experiment

BACKGROUND

Nitric oxide (NO) is important in respiratory physiology and airway defense. Although the paranasal sinuses are the major source of nasal NO, transport dynamics between the sinuses and nasal cavities are poorly understood.

METHODS

Exhaled nasal NO tracings were measured in two non-asthmatic subjects (one with allergic rhinitis, one without) using NO analyzer connected via face mask. We subsequently performed computational fluid dynamics NO emission simulations based on individual CT scans and compared to the experimental data.

RESULTS

Simulated exhaled NO tracings match well with experimental data (r > 0.84, p < 0.01) for both subjects, with measured peaks reaching 319.6 ppb in one subject (allergic-rhinitis), and 196.9 ppb in the other. The CFD simulation accurately captured the peak differences, even though the initial sinus NO concentration for both cases was set to the same 9000 ppb based on literature value. Further, the CFD simulation suggests that ethmoid sinuses contributed the most (>67%, other sinuses combined <33%) to total nasal NO emission in both cases and that diffusion contributes more than convective transport. By turning off diffusion (setting NO diffusivity to ~0), the NO emission peaks for both cases were reduced by >70%.

CONCLUSION

Historically, nasal NO emissions were thought to be contributed mostly by the maxillary sinuses (the largest sinuses) and active air movement (convection). Here, we showed that the ethmoid sinuses and diffusive transport dominate the process. These findings may have a substantial impact on our view of nasal NO emission mechanisms and sinus physiopathology in general.

The effect of decongestion on nasal airway patency and airflow

Nasal decongestant reduces blood flow to the nasal turbinates, reducing tissue volume and increasing nasal airway patency. This study maps the changes in nasal anatomy and measures how these changes affect nasal resistance, flow partitioning between superior and inferior cavity, flow patterns and wall shear stress. High-resolution MRI was applied to capture nasal anatomy in 10 healthy subjects before and after application of a topical decongestant. Computational fluid dynamics simulated nasal airflow at steady inspiratory flow rates of 15 L.min[Formula: see text] and 30 L.min[Formula: see text]. The results show decongestion mainly increases the cross-sectional area in the turbinate region and SAVR is reduced (median approximately 40[Formula: see text] reduction) in middle and lower parts of the cavity. Decongestion reduces nasal resistance by 50[Formula: see text] on average, while in the posterior cavity, nasal resistance decreases by a median factor of approximately 3 after decongestion. We also find decongestant regularises nasal airflow and alters the partitioning of flow, significantly decreasing flow through the superior portions of the nasal cavity. By comparing nasal anatomies and airflow in their normal state with that when pharmacologically decongested, this study provides data for a broad range of anatomy and airflow conditions, which may help characterize the extent of nasal variability.

Middle turbinate resection is unlikely to cause empty nose syndrome in first year postoperatively

PURPOSE

Empty nose syndrome (ENS) is characterized by nasal dryness, crusting, and paradoxical nasal obstruction most commonly after inferior turbinate resection. ENS has also been reported to occur after middle turbinate resection (MTR), and concern for causing ENS is a possible reason surgeons preserve the MT during endoscopic sinus surgery (ESS). The objective was to determine whether MTR during ESS led to ENS.

MATERIALS AND METHODS

This was a prospective case series of 95 consecutive patients that underwent bilateral subtotal MTR during ESS with either Draf IIB or Draf III frontal sinusotomies, for chronic rhinosinusitis with or without nasal polyps, and frontal sinus inverted papillomas. Demographic data and postoperative Empty Nose Syndrome 6-item Questionnaire (ENS6Q) scores were obtained. Nasal crusting was also documented on last postoperative nasal endoscopy.

RESULTS

Pathologies included chronic rhinosinusitis with nasal polyps (69), without nasal polyps (12), and inverted papillomas (14). Fifty-six patients underwent subtotal MTRs during ESS with Draf IIB, and 39 with Draf III. Mean follow-up was 19.4 months (range 12-49). Mean postoperative ENS6Q score was 2.1. Only 2.1% had ENS6Q scores ≥ 11, and 6.3% had nasal crusting at last follow-up. None of the patients with ENS6Q scores ≥ 11 had nasal crusting at last follow-up. There were no significant differences in outcomes between ages, genders, surgery types, or pathologies.

CONCLUSIONS

Patients who underwent bilateral subtotal MTR during ESS were unlikely to develop ENS by at least 1 year postoperatively, based on patients rarely experiencing ENS6Q scores ≥ 11 or persistent nasal crusting.

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.

Regional Peak Mucosal Cooling Predicts Radiofrequency Treatment Outcomes of Nasal Valve Obstruction

OBJECTIVES/HYPOTHESIS

Low energy radiofrequency may offer effective treatment for narrow or obstructed nasal valve, yet its precise mechanism is not fully understood.

STUDY DESIGN

Prospective, nonrandomized, case series.

METHODS

Twenty prospective patients with internal nasal valve obstruction underwent office-based Vivaer treatment (Aerin Medical, Inc) under local anesthesia. Computational fluid dynamics (CFD) models were constructed based on the pre- and 90 days post-procedure computed tomography (CT) scans to identify salient changes in nasal airflow parameters.

RESULTS

Patients' Nasal Obstruction Symptom Evaluation score (NOSE: pre-treatment 78.89 ± 11.57; post-treatment 31.39 ± 18.30, P = 5e-7) and Visual Analog Scale of nasal obstruction (VAS: pre-treatment 6.01 ± 1.83; post-treatment 3.44 ± 2.11, P = 1e-4) improved significantly at 90 days after the minimally invasive approach. Nasal airway volume in the treatment area increased ~7% 90 days post-treatment (pre-treatment 5.97 ± 1.20, post-treatment 6.38 ± 1.50 cm³ , P = .018), yet there were no statistically significant changes in the measured peak nasal inspiratory flowrate (PNIF, pre-treatment: 60.16 ± 34.49; post-treatment: 72.38 ± 43.66 ml/s; P = .13) and CFD computed nasal resistance (pre-treatment: 0.096 ± 0.065; post-treatment: 0.075 ± 0.026 Pa/(ml/s); P = .063). As validation, PNIF correlated significantly with nasal resistance (r = 0.47, P = .004). Among all the variables, only the peak mucosal cooling posterior to the nasal vestibule significantly correlated with the NOSE at baseline (r = -0.531, P = .023) and with post-treatment improvement (r = 0.659, P = .003).

CONCLUSION

Minimal remodeling of the nasal valve (7% in this study) may have a profound effect on perceived nasal obstruction, despite little effect on nasal resistance, or PNIF. The results corroborated our previous findings that subjective relief of nasal obstruction correlates with regional mucosal cooling rather than nasal resistance or peak flow rate, a potential target for future effective, personalized therapeutic approaches.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1760-E1769, 2021.

Is Respiratory Epithelial Adenomatoid Hamartoma Related to Central Compartment Atopic Disease?

BACKGROUND

Respiratory epithelial adenomatoid hamartoma (REAH) is a benign lesion of the sinonasal tract that may mimic more concerning pathology. Clinical factors associated with REAH have not been well characterized.

OBJECTIVE

To report our findings on patients with this pathologic diagnosis.

METHODS

A retrospective chart review of patients with REAH between September 2006 and November 2019 was conducted. Data collected included clinical allergic rhinitis and asthma history, additional sinonasal diagnoses, prior sinus surgery, and the location of the REAH within the sinonasal cavity.

RESULTS

Twenty-six patients were identified (53.8% male, mean age 62 years [range, 29-93]). Bilateral REAH occurred in 50%. REAH was located at the superior nasal septum in 84.6% cases, with the remainder identified in sinus contents submitted for pathology, making definitive site uncertain. Concurrent sinonasal inflammatory disorders were identified in 18 patients (69.2%), including chronic rhinosinusitis with nasal polyps-not otherwise specified (6), chronic rhinosinusitis without nasal polyps (4), aspirin-exacerbated respiratory disease (2), allergic fungal rhinosinusitis (1), central compartment atopic disease (5), and IgG4-related sclerosing disease (1). Eight patients had isolated REAH. Adequate allergy records were available for 19 patients, of which 18 of 19 (94.7%) had clinical allergic rhinitis.

CONCLUSIONS

REAH is a benign sinonasal lesion commonly located within the central compartment of the nasal cavity, a site of significant allergen exposure. Affected patients have a high incidence of allergy along with chronic inflammatory conditions. The coexistence of REAH within inflammatory nasal mucosa in a consistent anatomic location, suggests REAH may have a similar etiology to central compartment atopic disease, with resultant respiratory glandular ingrowth within long-standing reactive changes of mucosa derived from ethmoid embryologic origin.

The cotton test redistributes nasal airflow in patients with empty nose syndrome

BACKGROUND

Empty nose syndrome (ENS) remains a controversial disease primarily associated with inferior turbinate tissue loss. Cotton placement into the inferior meatus often alleviates ENS symptoms within minutes, but the physiologic explanation for this phenomenon is unknown. Computational fluid dynamics (CFD) was employed to evaluate the mechanisms of altered nasal airflow conferred by cotton testing.

METHODS

Six ENS patients (12 sides) with pre-existing sinus computed tomography (CT) imaging were enrolled after marked symptomatic improvement (decrease in score on the Empty Nose Syndrome 6-Item Questionnaire [ENS6Q] of >7 points) with office-based cotton testing. The fashioned cotton plug was labeled in situ with iohexol contrast spray, and sinus CT was immediately obtained to detect cotton contouring in the inferior meatus. CT imaging from pre- and post-cotton placement was analyzed using comparative CFD techniques.

RESULTS

After cotton placement, significant symptomatic improvement and reduced ENS6Q scores (16.8 ± 4.1 to 3.1 ± 2.4; p < 0.001) were recorded. Using CFD, cotton placement produced an expected 21% increase in upper airway resistance (p < 0.05). However, a significant shift in the nasal airflow distribution was also detected, with a transition of airflow vectors away from a middle meatus jetstream (-41%; p < 0.002).

CONCLUSION

Objective CFD assessment confirmed that the cotton test not only increases nasal resistance, but also restores airflow distribution to the inferior meatus in symptomatic ENS patients. These results highlight the potential efficacy of cotton test in ENS patients and further bolster the utility of this tool in identifying appropriate candidates for the inferior meatus augmentation procedure.

Assessing Changes in Airflow and Energy Loss in a Progressive Tracheal Compression Before and After Surgical Correction

The energy needed to drive airflow through the trachea normally constitutes a minor component of the work of breathing. However, with progressive tracheal compression, patient subjective symptoms can include severe breathing difficulties. Many patients suffer multiple respiratory co-morbidities and so it is important to assess compression effects when evaluating the need for surgery. This work describes the use of computational prediction to determine airflow resistance in compressed tracheal geometries reconstructed from a series of CT scans. Using energy flux analysis, the regions that contribute the most to airway resistance during inhalation are identified. The principal such region is where flow emerging from the zone of maximum constriction undergoes breakup and turbulent mixing. Secondary regions are also found below the tongue base and around the glottis, with overall airway resistance scaling nearly quadratically with flow rate. Since the anatomical extent of the imaged airway varied between scans-as commonly occurs with clinical data and when assessing reported differences between research studies-the effect of sub-glottic inflow truncation is considered. Analysis shows truncation alters the location of jet breakup and weakly influences the pattern of pressure recovery. Tests also show that placing a simple artificial glottis in the inflow to a truncated model can replicate patterns of energy loss in more extensive models, suggesting a means to assess sensitivity to domain truncation in tracheal airflow simulations.

Peak Sinus Pressures During Sneezing in Healthy Controls and Post-Skull Base Surgery Patients

OBJECTIVES/HYPOTHESIS

Patients are frequently advised to sneeze with an open mouth and avoid nose-blowing following an endoscopic endonasal approache (EEA) to the skull base, despite a lack of quantitative evidence. This study applies computational fluid dynamics (CFD) to quantify sinus pressures along the skull base during sneezing.

STUDY DESIGN

Case-control series.

METHODS

Computed tomography or magnetic resonance imaging scans of four post-EEA patients and four healthy controls were collected and analyzed utilizing CFD techniques. A pressure drop of 6,000 Pa was applied to the nasopharynx based on values in the literature to simulate expiratory nasal airflow during sneezing. Peak pressures along the skull base in frontal, ethmoid, and sphenoid sinuses were collected.

RESULTS

Significant increases in skull base peak pressure was observed during sneezing, with significant individual variations from 2,185 to 5,685 Pa. Interestingly, healthy controls had significantly higher pressures compared to post-EEA patients (5179.37 ± 198.42 Pa vs. patients 3,347.82 ± 1,472.20 Pa, P < .05), which could be related to higher anterior nasal resistance in unoperated healthy controls (0.44 ± 0.22 vs. 0.31 ± 0.16 Pa/mL/sec for patients, P = .38). The sinus pressure buildup may be due to airway resistance functioning as a valve preventing air from being released quickly. Supporting this theory, there was a strong correlation (r = 0.82) between peak skull base pressure and the ratio of anterior resistance to total resistance. Within-subject variation in pressures between different skull base regions was much lower (average = ~5%).

CONCLUSIONS

This study provided the first quantitative analysis of air pressure along the skull base during sneezing in post-EEA patients through CFD, suggesting that pressure buildup may depend on individual anatomy.

LEVEL OF EVIDENCE

3b Laryngoscope, 130:2138-2143, 2020.

Hemodynamics of neonatal double lumen cannula malposition

Objective:

Malposition of dual lumen cannula is a frequent and challenging complication in neonates and plays a significant role in shaping the in vitro device hemodynamics. This study aims to analyze the effect of the dual lumen cannula malposition on right-atrial hemodynamics in neonatal patients using an experimentally validated computational fluid dynamics model.

Methods:

A computer model was developed for clinically approved dual lumen cannula (13Fr Origen Biomedical, Austin, Texas, USA) oriented inside the atrium of a 3-kg neonate with normal venous return. Atrial hemodynamics and dual lumen cannula malposition were systematically simulated for two rotations (antero-atrial and atrio-septal) and four translations (two intravascular movements along inferior vena cava and two dislodged configurations in the atrium). A multi-domain compartmentalized mesh was prepared to allow the site-specific evaluation of important hemodynamic parameters. Transport of each blood stream, blood damage levels, and recirculation times are quantified and compared to dual lumen cannula in proper position.

Results:

High recirculation levels (39 ± 4%) in malpositioned cases resulted in poor oxygen saturation where maximum recirculation of up to 42% was observed. Apparently, Origen dual lumen cannula showed poor inferior vena cava blood–capturing efficiency (48 ± 8%) but high superior vena cava blood–capturing efficiency (86 ± 10%). Dual lumen cannula malposition resulted in corresponding changes in residence time (1.7 ± 0.5 seconds through the tricuspid). No significant differences in blood damage were observed among the simulated cases compared to normal orientation. Compared to the correct dual lumen cannula position, both rotational and translational displacements of the dual lumen cannula resulted in significant hemodynamic differences.

Conclusion:

Rotational or translational movement of dual lumen cannula is the determining factor for atrial hemodynamics, venous capturing efficiency, blood residence time, and oxygenated blood delivery. Results obtained through computational fluid dynamics methodology can provide valuable foresight in assessing the performance of the dual lumen cannula in patient-specific configurations.

Central compartment involvement in aspirin-exacerbated respiratory disease: the role of allergy and previous sinus surgery

BACKGROUND

Evidence for a relationship between allergy and chronic rhinosinusitus with nasal polyps (CRSwNP) is equivocal. Central compartment (CC) atopic disease is a nasal inflammatory condition related to inhalant allergy. CC involvement is common in aspirin-exacerbated respiratory disease (AERD), a subset of CRSwNP, and we hypothesize it is related to allergic status.

METHODS

This study was a retrospective analysis of a single-institution database for the January 2016 to February 2019 time period. Data regarding endoscopic CC findings, clinical allergy history, and results of allergy testing were collected. Statistical analysis was performed, with significance set at p < 0.05.

RESULTS

Seventy-two AERD patients met the inclusion criteria. Fifty-nine patients had CC involvement (53 bilateral, 6 unilateral). For patients with documented allergy status, 100% of patients with endoscopic CC disease had clinical allergic rhinitis (AR), and 45 of 48 (93.8%) had positive allergy testing. Thirteen patients had no CC involvement (4 with clinical AR; 3 of 7 with positive allergy testing). CC endoscopic findings in AERD were significantly associated with clinical allergy (p < 0.0001, phi = 0.771). Overall, patients with CC involvement averaged 3.8 surgeries vs 3.2 for those without CC involvement (p = not statistically significant). However, patients with septal involvement averaged 4.2 surgeries vs 2.0 for those without septal involvement (p = 0.004). As the number of sinus surgeries increases, middle turbinate (MT) resection (r = 0.300, p = 0.022) and septal involvement (r = 0.372, p = 0.004) significantly increase. All patients with MT resection had septal disease, whereas none without CC disease had MT resection.

CONCLUSION

Most AERD patients exhibit AR, and this correlates with CC disease. As the number of surgeries increases, MT resection may predispose to polyposis of the septum.

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.

Complications Are Rare From Middle Turbinate Resection: A Prospective Case Series

Background

When chronic rhinosinusitis with nasal polyps (CRSwNP) fails to respond to medical therapy, endoscopic sinus surgery (ESS) plays an integral role in management. Some studies have shown that middle turbinate resection (MTR) during ESS leads to decreased polyp recurrence and revision ESS rates. Other studies suggest MTR can lead to complications.

Objective

The purpose of this study was to assess the safety of MTR during ESS for CRSwNP by determining the incidences of intraoperative cerebrospinal fluid (CSF) leak, postoperative epistaxis requiring operative intervention, and postoperative complete frontal stenosis.

Methods

A multiinstitutional, prospective case series of 91 adult CRSwNP patients was conducted. Patients with medically refractory CRSwNP underwent primary or revision ESS plus MTR by 3 surgeons. Two of the surgeons performed partial MTRs, and one of the surgeons performed complete MTRs. Patients were evaluated for the following complications: intraoperative CSF leak during MTR, postoperative epistaxis requiring operative intervention, and postoperative complete frontal ostial stenosis. Secondary outcomes included changes from preoperative to postoperative 22-item Sinonasal Outcome Test (SNOT-22) scores and revision ESS rates.

Results

Unilateral or bilateral complete ESSs with MTRs were performed on 91 CRSwNP patients. In total, 173 MTRs were performed. Two surgeons performed 97 partial MTRs on 49 patients, and the third surgeon performed 76 complete MTRs on 42 patients. One CSF leak occurred during partial MTR (1/173, 0.57%). No patients suffered postoperative epistaxis requiring operative intervention, and no patients developed complete frontal stenosis. From preoperatively to postoperatively, mean SNOT-22 scores decreased from 53.7 to 13.1 ( P = .001). No revision ESS was needed during the follow-up period. Mean follow-up time was 7.5 ± 5.4 months.

Conclusions

Partial and complete MTR during ESS for CRSwNP in this cohort resulted in very low, acceptable intraoperative and short-term postoperative complication rates and no detriment to SNOT-22 scores.

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.

The Application of Computational Fluid Dynamics in the Evaluation of Laryngotracheal Pathology

OBJECTIVES

Laryngotracheal stenosis and obstruction can be challenging to manage. Traditional assessment tools are limited in clinical correlation. Three-dimensional computational fluid dynamics (CFD) modeling is a novel technique used to analyze airflow dynamics. The objective of this study was to apply CFD to the human upper airway to explore its utility.

METHODS

CFD models were constructed on an adult patient with an obstructive tracheal lesion before and after intervention and on an adult with normal airway anatomy, using computed tomographic imaging obtained retrospectively. Key airflow metrics were calculated.

RESULTS

CFD provided detailed airway geometry. The normal airway had a peak flow velocity of 3.12 m/s, wall shear stress of 0.30 Pa, and resistance of 0.02 Pa/mL/s. The pathologic patient showed an elevated peak flow velocity of 12.25 m/s, wall shear stress of 3.90 Pa, and resistance of 0.22 Pa/mL/s. This was reflected clinically with dyspnea, stridor, and obstructive impairment via pulmonary function testing. Following treatment, peak flow velocity corrected to 3.95 m/s, wall shear stress to 0.72Pa, and resistance to 0.01 Pa/mL/s. Cross-sectional area improved to 190 mm² from a minimum of 53 mm² at the same segment. Stridor and dyspnea resolved.

CONCLUSIONS

CFD metrics were calculated on the normal, diseased, and posttreatment upper airway. Variations were reflected in clinical symptoms. These methods could model surgical outcomes and anticipate disease severity.

Impact of Middle Turbinectomy on Airflow to the Olfactory Cleft: A Computational Fluid Dynamics Study

BACKGROUND

The impact of middle turbinate resection (MTR) on olfaction remains a point of debate in the current literature. Few studies have objectively evaluated olfactory cleft airflow following MTR; thus, the mechanism by which MTR may impact olfaction is poorly understood. It is not known whether the postsurgical changes in airway volume, flow, and resistance increase odorant transport or disrupt the patterns of normal airflow. Computational fluid dynamics can be used to study the nasal airway and predict responses to surgical intervention.

OBJECTIVE

To evaluate the functional impact of MTR on nasal airflow, resistance, and olfaction.

METHODS

Five maxillofacial computed tomography scans of patients without signs of significant sinusitis or nasal polyposis were used. Control models for each patient were compared to their corresponding model after virtual total MTR. For each model, nasal airway volume, nasal resistance, and air flow rate were determined. Odorant transport of 3 different odorants in the nasal cavity was simulated based on the computed steady airflow field.

RESULTS

Total airflow significantly increased following bilateral MTR in all patient models ( P < .05). Consistent with our airflow results, we found a decrease in nasal resistance following MTR. MTR significantly increased area averaged flux to the olfactory cleft when compared to controls for phenylethyl alcohol (high-sorptive odorant). Results for carvone (medium sorptive) were similarly elevated. MTR impact on limonene, a low flux odorant, was equivocal.

CONCLUSION

MTR increases nasal airflow while decreasing the nasal resistance. Overall, olfactory flux increased for high sorptive (phenylethyl alcohol) and medium sorpitve (l-carvone) odorants. However, the significant variation observed in one of our models suggests that the effects of MTR on the nasal airflow and the resultant olfaction can vary between individuals based on individual anatomic differences.

Computational fluid dynamics after endoscopic endonasal skull base surgery-possible empty nose syndrome in the context of middle turbinate resection

BACKGROUND

Empty nose syndrome (ENS) is a rare and debilitating disease with a controversial definition, etiology, and treatment. One puzzling fact is that patients who undergo an endoscopic endonasal approach (EEA) often have resection of multiple anatomic structures, yet seldom develop ENS. In this pilot study, we analyzed and compared the computational fluid dynamics (CFD) and symptoms among post-EEA patients, ENS patients, and healthy subjects.

METHODS

Computed tomography scans of 4 post-EEA patients were collected and analyzed using CFD techniques. Two patients had significant ENS symptoms based on results of the Empty Nose Syndrome 6-item Questionnaire (score >11), whereas the other 2 were asymptomatic. As a reference, their results were compared with previously published CFD results of 27 non-EEA ENS patients and 42 healthy controls.

RESULTS

Post-EEA patients with ENS symptoms had a similar nasal airflow pattern as non-EEA ENS patients. This pattern differed significantly from that of EEA patients without ENS symptoms and healthy controls. Overall, groups with ENS symptoms exhibited airflow dominant in the middle meatus region and a significantly lower percentage of airflow in the inferior turbinate region (EEA with ENS, 17.74 ± 4.00% vs EEA without ENS, 51.25 ± 3.33% [t test, p < 0.02]; non-EEA ENS, 25.8 ± 17.6%; healthy subjects, 36.5 ± 15.9%) as well as lower peak wall shear stress (EEA with ENS, 0.30 ± 0.13 Pa vs EEA without ENS, 0.61 ± 0.03 Pa [p = 0.003]; non-EEA ENS, 0.58 ± 0.24 Pa; healthy subjects, 1.18 ± 0.81 Pa).

CONCLUSION

These results suggest that turbinectomy and/or posterior septectomy may have a varying functional impact and that ENS symptoms go beyond anatomy and correlate with aerodynamic changes. The findings open the door for CFD as a potential objective diagnosis tool for ENS.

Modeling congenital nasal pyriform aperture stenosis using computational fluid dynamics

OBJECTIVES

Congenital nasal pyriform aperture stenosis (CNPAS) is a rare cause of airway obstruction in the neonate. Computational airway modeling has not been done in neonates and young infants to understand the impact of stenosis on functional nasal airflow. In this study, we 1) applied computational fluid dynamics (CFD) model to the airway of a neonate with CNPAS and 2) compare airflow dynamics of a normal and CNPAS airway.

METHODS

Three-dimensional models of the nasal airway of a normal neonate and a neonate with CNPAS were created using computed tomography scans of the facial bones. Measured anatomic parameters included volume, surface area, and cross-sectional area. CFD simulation was then performed. Simulated flow parameters included pressure, average velocity, and resistance.

RESULTS

The neonate with CNPAS had a lesser volume (2.74 cm³ vs. 4.50 cm³) and surface area (18.8 cm² vs. 45.5 cm²) than the normal airway. The CNPAS airway had a lesser bilateral cross-sectional area and average cross-sectional velocity throughout the length of the model. While there is a large pressure drop in the normal airway immediately after the entry point, the pressure drop in the CNPAS airway occurs more posteriorly. The total nasal resistance was approximately eight-fold greater in the CNPAS airway than the normal.

CONCLUSIONS

CFD analysis can be performed on airways of neonates with nasal obstruction, such as in CNPAS. A CFD model may help characterize severity of airway obstruction as it can predict the three-dimensional pattern of airflow. Determining the role of CFD in clinical management of CNPAS requires further investigation.

The Influence of Sniffing on Airflow and Odorant Deposition in the Canine Nasal Cavity

Nasal airflow plays a critical role in olfaction by transporting odorant from the environment to the olfactory epithelium, where chemical detection occurs. Most studies of olfaction neglect the unsteadiness of sniffing and assume that nasal airflow and odorant transport are "quasi-steady," wherein reality most mammals "sniff." Here, we perform computational fluid dynamics simulations of airflow and odorant deposition in an anatomically accurate model of the coyote (Canis latrans) nasal cavity during quiet breathing, a notional quasi-steady sniff, and unsteady sniffing to: quantify the influence of unsteady sniffing, assess the validity of the quasi-steady assumption, and investigate the functional advantages of sniffing compared to breathing. Our results reveal that flow unsteadiness during sniffing does not appreciably influence qualitative (gross airflow and odorant deposition patterns) or quantitative (time-averaged olfactory flow rate and odorant uptake) measures of olfactory function. A quasi-steady approximation is, therefore, justified for simulating time-averaged olfactory function in the canine nose. Simulations of sniffing versus quiet breathing demonstrate that sniffing delivers about 2.5 times more air to the olfactory recess and results in 2.5-3 times more uptake of highly- and moderately-soluble odorants in the sensory region per unit time, suggesting one reason why dogs actively sniff. Simulations also reveal significantly different deposition patterns in the olfactory region during inspiration for different odorants, and that during expiration there is little retronasal odorant deposition in the sensory region. These results significantly improve our understanding of canine olfaction, and have several practical implications regarding computer simulation of olfactory function.

The Middle Turbinate Resection and Its Repercussion in Olfaction with the University of Pennsylvania Smell Identification Test (UPSIT)

Introduction  Nasal obstruction is a common complaint, and, for some, the middle turbinate resection is still a controversial issue among the surgical options due to the possibility of deleterious effects on olfaction. The University of Pennsylvania smell identification test (UPSIT) is considered the gold standard of smell identification tests, but data about it is still incipient in Brazil.

Objective  To evaluate if the middle turbinectomy has any repercussion on the sense of olfaction by using the UPSIT as an assessment tool.

Methods  A prospective study performed between 2013 and 2015 with 27 patients who were treated with middle turbinectomy by the same surgeon and tested with the UPSIT pre- and post-surgery, with a minimum interval of 3 months.

Results  Twenty-five patients completed the study. The mean age was 27.9 years. There was no statistical correlation between middle turbinectomy and the UPSIT score, or between gender and the UPSIT score.

Conclusion  There was no clinical repercussion on olfaction from partial middle turbinectomy.

Computational modeling and validation of human nasal airflow under various breathing conditions

The human nose serves vital physiological functions, including warming, filtration, humidification, and olfaction. These functions are based on transport phenomena that depend on nasal airflow patterns and turbulence. Accurate prediction of these airflow properties requires careful selection of computational fluid dynamics models and rigorous validation. The validation studies in the past have been limited by poor representations of the complex nasal geometry, lack of detailed airflow comparisons, and restricted ranges of flow rate. The objective of this study is to validate various numerical methods based on an anatomically accurate nasal model against published experimentally measured data under breathing flow rates from 180 to 1100ml/s. The numerical results of velocity profiles and turbulence intensities were obtained using the laminar model, four widely used Reynolds-averaged Navier-Stokes (RANS) turbulence models (i.e., k-ε, standard k-ω, Shear Stress Transport k-ω, and Reynolds Stress Model), large eddy simulation (LES) model, and direct numerical simulation (DNS). It was found that, despite certain irregularity in the flow field, the laminar model achieved good agreement with experimental results under restful breathing condition (180ml/s) and performed better than the RANS models. As the breathing flow rate increased, the RANS models achieved more accurate predictions but still performed worse than LES and DNS. As expected, LES and DNS can provide accurate predictions of the nasal airflow under all flow conditions but have an approximately 100-fold higher computational cost. Among all the RANS models tested, the standard k-ω model agrees most closely with the experimental values in terms of velocity profile and turbulence intensity.

Computational fluid dynamics evaluation of posterior septectomy as a viable treatment option for large septal perforations

BACKGROUND

Numerous surgical techniques exist to treat nasal septal perforation (NSP). The surgical closure of large NSPs (>2 cm) is still challenging. Posterior septectomy has been reported as a simple alternative to treat large NSP, yet its mechanisms for symptom relief are not clear, and if failed, its consequence cannot be easily reversed.

METHODS

Ten NSP patients were recruited: 5 underwent posterior septectomy and 5 underwent conventional flap or button repair. Computational fluid dynamics (CFD) simulated the nasal aerodynamics based on computed tomography (CT) scans. All patients had preoperative CT; however, only 4 had postoperative CT: 2 underwent posterior septectomy and the other 2 underwent flap repair. We examined surgical outcomes and the nasal airflow features among the 2 treatment options.

RESULTS

Both groups of patients had good outcomes based on chart review. Patients undergoing septectomy had significantly larger perforation size (2.32 ± 0.87 vs 1.21 ± 0.60 cm), higher flow rate across the perforation (47.8 ± 28.6 vs 18.3 ± 12.2 mL/second), and higher wall shear stress (WSS) along the posterior perforation margin (1.39 ± 0.52 vs 1.15 ± 0.58 Pa). The posterior WSS significantly correlated with crossover flow velocity (r = 0.77, p = 0.009) and was reduced by almost 67% postseptectomy, and by 29% postrepair.

CONCLUSION

This is the first CFD analysis on an NSP patient cohort. NSP resulted in flow disturbance and increased WSS that potentially led to symptomatology. The removal of high stress points along the posterior margin may explain why posterior septectomy can be an effective treatment option. Aerodynamic abnormalities, in addition to perforation size and location, could serve as basis for future treatment decisions.

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.

Tour of a labyrinth: exploring the vertebrate nose

This special issue of The Anatomical Record is the outcome of a symposium entitled "Inside the Vertebrate Nose: Evolution, Structure and Function." The skeletal framework of the nasal cavity is a complicated structure that often houses sinuses and comprises an internal skeleton of bone or cartilage that can vary greatly in architecture among species. The nose serves multiple functions, including olfaction and respiratory air-conditioning, and its morphology is constrained by evolution, development, and conflicting demands on cranial space, such as enlarged orbits. The nasal cavity of vertebrates has received much more attention in the last decade due to the emergence of nondestructive methods that allow improved visualization of the internal anatomy of the skull, such as high-resolution x-ray computed tomography and magnetic resonance imaging. The 17 articles included here represent a broad range of investigators, from paleontologists to engineers, who approach the nose from different perspectives. Key topics include the evolution and development of the nose, its comparative anatomy and function, and airflow through the nasal cavity of individual species. In addition, this special issue includes review articles on anatomical reduction of the olfactory apparatus in both cetaceans and primates (the vomeronasal system), as well as the molecular biology of olfaction in vertebrates. Together these articles provide an expansive summary of our current understanding of vertebrate nasal anatomy and function. In this introduction, we provide background information and an overview of each of the three primary topics, and place each article within the context of previous research and the major challenges that lie ahead.

Respiratory and olfactory turbinals in feliform and caniform carnivorans: the influence of snout length

To enhance bite force at the canines, feliform carnivorans have short rostra relative to caniform carnivorans. Rostral reduction in feliforms results in less rostrocaudal space for the maxilloturbinals, the complex set of bones involved in conditioning inspired air and conserving water. It is unknown whether the maxilloturbinals might show adaptations to adjust for this loss, such as greater complexity than what is observed in longer snouted caniforms. To understand the impact of rostral shortening on turbinals in feliforms, we used high resolution CT scans to quantify turbinal surface areas (SA) in 16 feliforms and compared them with published data on 20 caniforms. Results indicate that feliforms have reduced maxilloturbinal SA for their body mass relative to caniforms, but comparable fronto-ethmoturbinal SA. However, anterior portions of the ethmoturbinals in feliforms extend forward into the snout and are positioned within the respiratory pathway. When the SA of these anterior ethmoturbinals is added to maxilloturbinal SA to produce an estimated respiratory SA, feliforms and caniforms are similar in respiratory SA. This transfer of ethmoturbinal SA to respiratory function results in feliforms having less estimated olfactory SA relative to caniforms. Previous work on canids found a positive association between olfactory surface area and diet, but this was not found for felids. Results are consistent with feliforms having somewhat reduced olfactory ability relative to caniforms. If confirmed by behavioral data, the relative reduction in olfactory SA in many feliforms may reflect a greater reliance on vision in foraging relative to caniforms.