Dennis O. Frank

Changes in nasal airflow and heat transfer correlate with symptom improvement after surgery for nasal obstruction.

Surgeries to correct nasal airway obstruction (NAO) often have less than desirable outcomes, partly due to the absence of an objective tool to select the most appropriate surgical approach for each patient. Computational fluid dynamics (CFD) models can be used to investigate nasal airflow, but variables need to be identified that can detect surgical changes and correlate with patient symptoms. CFD models were constructed from pre- and post-surgery computed tomography scans for 10 NAO patients showing no evidence of nasal cycling. Steady-state inspiratory airflow, nasal resistance, wall shear stress, and heat flux were computed for the main nasal cavity from nostrils to posterior nasal septum both bilaterally and unilaterally. Paired t-tests indicated that all CFD variables were significantly changed by surgery when calculated on the most obstructed side, and that airflow, nasal resistance, and heat flux were significantly changed bilaterally as well. Moderate linear correlations with patient-reported symptoms were found for airflow, heat flux, unilateral allocation of airflow, and unilateral nasal resistance as a fraction of bilateral nasal resistance when calculated on the most obstructed nasal side, suggesting that these variables may be useful for evaluating the efficacy of nasal surgery objectively. Similarity in the strengths of these correlations suggests that patient-reported symptoms may represent a constellation of effects and that these variables should be tracked concurrently during future virtual surgery planning.

Role of Virtual Surgery in Preoperative Planning: Assessing the Individual Components of Functional Nasal Airway Surgery

OBJECTIVES To demonstrate the effect of individual components of functional nasal airway surgery in a patient with multifactorial obstruction and to discuss the potential benefit of computational fluid dynamics (CFD)–aided virtual surgery. METHODS A 53-year-old woman underwent septoplasty,turbinate reduction, and nasal valve repair. Presurgery and postsurgery digital nasal models were created from computed tomographic images, and nasal resistance was calculated using CFD techniques. The digital models were then manipulated to isolate the effects of the components of the surgery, creating a nasal valverepair alone model and a septoplasty/turbinate reduction alone model. RESULTS Bilateral nasal resistance in the postsurgery model was approximately 25% less than presurgery values.Similarly, CFD analysis showed reductions in nasal resistance of the virtual models: 19% reduction with intranasal surgery alone and 6% reduction with nasal valve repair alone. CONCLUSIONS Most of the reduction in nasal resistance was accomplished with performance of septoplasty and inferior turbinate reduction. The contribution of nasal valve repair was less in comparison but not insignificant.This pilot study implies that CFD-aided virtual surgery may be useful as part of preoperative planning inpatients with multifactorial anatomical nasal airwayobstruction

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

Background Nasal airway obstruction (NAO) is a common health condition impacting mood, energy, recreation, sleep, and overall quality of life. Nasal surgery often addresses NAO but the results are sometimes unsatisfactory. Evaluating surgical treatment efficacy could be improved if objective tests were available that correlated with patient-reported measures of symptoms. The goal of this study was to develop methods for comparing nasal resistance computed by computational fluid dynamics (CFD) models with patient-reported symptoms of NAO using early data from a 4-year prospective study. Methods Computed tomography (CT) scans and patient-reported scores from the Nasal Obstruction Symptom Evaluation (NOSE) scale and a visual analog scale (VAS) measuring unilateral airflow sensation were obtained pre- and postoperatively in two NAO patients showing no significant mucosal asymmetry who were successfully treated with functional nasal surgery, including septoplasty. Pre- and postsurgery CFD models were created from the CT scans. Numerical simulation of steady-state inspiratory airflow was used to calculate bilateral and unilateral CFD-derived nasal resistance (CFD-NR). Results In both subjects, NOSE and VAS scores improved after surgery, bilateral CFD-NR decreased, and unilateral CFD-NR decreased on the affected side. In addition, NOSE and VAS scores tracked with unilateral CFD-NR on the affected side. Conclusion These preliminary results suggest a possible correlation between unilateral NR and patient-reported symptoms and imply that analysis of unilateral obstruction should focus on the affected side. A formal investigation of unilateral CFD-NR and patient-reported symptoms in a series of NAO patients is needed to determine if these variables are correlated.BACKGROUND Nasal airway obstruction (NAO) is a common health condition impacting mood, energy, recreation, sleep, and overall quality of life. Nasal surgery often addresses NAO but the results are sometimes unsatisfactory. Evaluating surgical treatment efficacy could be improved if objective tests were available that correlated with patient-reported measures of symptoms. The goal of this study was to develop methods for comparing nasal resistance computed by computational fluid dynamics (CFD) models with patient-reported symptoms of NAO using early data from a 4-year prospective study. METHODS Computed tomography (CT) scans and patient-reported scores from the Nasal Obstruction Symptom Evaluation (NOSE) scale and a visual analog scale (VAS) measuring unilateral airflow sensation were obtained pre- and postoperatively in two NAO patients showing no significant mucosal asymmetry who were successfully treated with functional nasal surgery, including septoplasty. Pre- and postsurgery CFD models were created from the CT scans. Numerical simulation of steady-state inspiratory airflow was used to calculate bilateral and unilateral CFD-derived nasal resistance (CFD-NR). RESULTS In both subjects, NOSE and VAS scores improved after surgery, bilateral CFD-NR decreased, and unilateral CFD-NR decreased on the affected side. In addition, NOSE and VAS scores tracked with unilateral CFD-NR on the affected side. CONCLUSION These preliminary results suggest a possible correlation between unilateral NR and patient-reported symptoms and imply that analysis of unilateral obstruction should focus on the affected side. A formal investigation of unilateral CFD-NR and patient-reported symptoms in a series of NAO patients is needed to determine if these variables are correlated.

Modeling Nasal Physiology Changes due to Septal Perforations

Objective To use computational fluid dynamics (CFD) technology to help providers understand (1) how septal perforations may alter nasal physiology and (2) how these alterations are influenced by perforation size and location. Study Design Computer simulation study. Setting Facial plastic and reconstructive surgery clinic. Subjects and Methods With the aid of medical imaging and modeling software, septal perforations of 1 and 2 cm in anterior, posterior, and superior locations were virtually created in a nasal cavity digital model. The CFD techniques were used to analyze airflow, nasal resistance, air conditioning, and wall shear stress. Results Bilateral nasal resistance was not significantly altered by a septal perforation. Airflow allocation changed, with more air flowing through the lower-resistance nasal cavity. This effect was greater for anterior and posterior perforations than for the superior location. At the perforation sites, there was less localized heat and moisture flux and wall shear stress in superior perforations compared with those in anterior or posterior locations. For anterior perforations, a larger size produced higher wall shear and velocity, whereas in posterior perforations, a smaller size produced higher wall shear and velocity. Conclusion Septal perforations may alter nasal physiology. In the subject studied, airflow allocation to each side was changed as air was shunted through the perforation to the lower-resistance nasal cavity. Anterior and posterior perforations caused larger effects than those in a superior location. Increasing the size of anterior perforations and decreasing the size of posterior perforations enhanced alterations in wall shear and velocity at the perforation.

Effects of Anatomy and Particle Size on Nasal Sprays and Nebulizers

Objective. To study the effects of nasal deformity on aerosol penetration past the nasal valve (NV) for varying particle sizes using sprays or nebulizers. Study Design. Computed mathematical nasal airway model. Setting. Department computer lab. Subjects and Methods. Particle deposition was analyzed using a computational fluid dynamics model of the human nose with leftward septal deviation and compensatory right inferior turbinate hypertrophy. Sprays were simulated for 10 µm, 20 µm, 50 µm, or particle sizes following a Rosin Rammler particle size distribution (10-110 µm), at speeds of 1, 3, or 10 meters per second. Nebulization was simulated for 1, 3.2, 6.42, or 10 µm particles. Steady state inspiratory airflow was simulated at 15.7 liters per minute. Results. Sprays predicted higher NV penetration on the right side for particle sizes >10 µm, with comparable penetration on both sides at 10 µm. Nearly 100% deposited in the nasal passages for all spray characteristics. Nebulizer predictions showed nearly 100% of particles <6.42 µm and more than 50% of 6.42 µm bypassing both sides of the nose without depositing. Of the nebulized particles that deposited, penetration was higher on the right at 10 µm, with comparable penetration on both sides at 6.42 µm. Spray penetration was highest at 10 µm, with more than 96% penetrating on both sides at 1 and 3 meters per second. Nebulization penetration was also highest at 10 µm (40% on the left, >90% on the right). Conclusion. In the presence of a septal deviation, sprays or nebulizers containing 10-µm particles may have good penetration beyond the NV. Nebulized particles <10 µm are likely to be respirable. Additionally, spray speeds above 3 meters per second may limit penetration.

Quantification of airflow into the maxillary sinuses before and after functional endoscopic sinus surgery.

The effects of increases in maxillary sinus (MS) airflow following functional endoscopic sinus surgery (FESS) are unknown. The goal of this study was to quantify the effects of FESS on airflow into the MS in a cohort of patients with chronic rhinosinusitis, and compare MS flow rate with patient‐reported outcome measures.

Deviated nasal septum hinders intranasal sprays: a computer simulation study.

BACKGROUND This study investigates how deviated nasal septum affects the quantity and distribution of spray particles, and examines the effects of inspiratory airflow and head position on particle transport. METHODS Deposition of spray particles was analysed using a three-dimensional computational fluid dynamics model created from a computed tomography scan of a human nose with leftward septal deviation and a right inferior turbinate hypertrophy. Five simulations were conducted using FluentTM software, with particle sizes ranging from 20-110 μm, a spray speed of 3 m/s, plume angle of 68(deg), and with steady state inspiratory airflow either present (15.7 L/min) or absent at varying head positions. RESULTS With inspiratory airflow present, posterior deposition on the obstructed side was approximately four times less than the contralateral side, regardless of head position, and was statistically significant. When airflow was absent, predicted deposition beyond the nasal valve on the left and right sides were between 16% and 69% lower and positively influenced by a dependent head position. CONCLUSION Simulations predicted that septal deviation significantly diminished drug delivery on the obstructed side. Furthermore, increased particle penetration was associated with presence of nasal airflow. Head position is an important factor in particle deposition patterns when inspiratory airflow is absent.

Computed intranasal spray penetration: comparisons before and after nasal surgery.

Quantitative methods for comparing intranasal drug delivery efficiencies pre‐ and postoperatively have not been fully utilized. The objective of this study is to use computational fluid dynamics techniques to evaluate aqueous nasal spray penetration efficiencies before and after surgical correction of intranasal anatomic deformities.

Effects of Anatomy and Particle Size on Nasal Sprays

Objective: Compare spray penetration past the nasal valve (NV) predicted for particle sizes at varying spray speeds using a computational fluid dynamics (CFD) model of the human nasal cavity with septal deviation on the left side and inferior turbinate hypertrophy on the right. Method: Simulations using Fluent (ANSYS, Inc, Lebanon, New Hampshire) were carried out for 10 µm, 20 µm, 50 µm, or particle sizes following a Rosin Rammler Particle Size Distribution (RRPSD) ranging from 10-110µm. Spray speed was 1 m/s, 3 m/s, or 10 m/s; steady state inspiratory airflow rate was 15.7 L/min. Results: Simulations predicted at least 2 times higher NV penetration on the right side (hypertrophic turbinate) than the left (septal deviation) for most particle sizes and spray speeds. Simulated penetration of 10 µm particles at 1 m/s was 100% with none escaping via the nasopharynx. At 3 and 10 m/s, more simulated 10µm particles escaped the nose than other sizes. Maximum penetration of RRPSD, 20µm, and 50µm particles was predicted to be 15%, 35%, and 12% on the left side, and 52%, 58%, and 56% on the right, respectively, occurring at 1m/s for RRPSD and 50 µm, and 3 m/s for 20 µm. Conclusion: In the presence of a septal deviation, sprays containing 10 µm particles may have better penetration past the NV. Additionally, increasing spray speed (above 3m/s) appears to limit spray penetration, suggesting that patients should be discouraged from spraying medications forcefully, as this could limit penetration of the drug.

Does Perception of Nasal Patency Correlate with Mucosal Cooling after Surgery for Nasal Obstruction

Objectives: 1) Quantify heat fluxes (ie, mucosal cooling) spatially in the nasal passages of nasal airway obstruction (NAO) patients before and after surgery using computational fluid dynamics (CFD). 2) Develop methods to correlate heat fluxes with patient-reported symptoms, as measured by the nasal obstruction symptom evaluation (NOSE) and the visual analog score (VAS). Methods: Computed tomography (CT) scans of 10 patients were obtained before and after surgery to relieve NAO. Three-dimensional models of each patient’s nasal anatomy were used to run steady-state CFD simulations of airflow and heat transfer during inspiration. The importance of anatomic location for perception of nasal patency was evaluated by comparing heat fluxes in the nasal vestibule vs. the entire nasal cavity, and by evaluating the percentage of nasal mucosa exposed to heat fluxes greater than 500 W/m2. Results: Post-operatively, heat fluxes were statistically higher on the pre-operative most obstructed side, for the nasal vestibule alone and the entire nasal cavity (p values < 0.01). A larger area of nasal mucosa was exposed to heat fluxes > 500 W/m2 after surgery than before. The best correlation between subjective and objective measures of nasal patency was obtained for NOSE against heat flux in the entire most obstructed nasal cavity (r = −0.81). Conclusions: A significant increase in heat fluxes (ie, mucosal cooling) correlates well with patients’ perception of better nasal patency after NAO surgery. CFD-derived heat fluxes may prove to be a valuable predictor of success in NAO surgery.