An adjoint-based approach for the surgical correction of nasal septal deviations.

Deviations of the septal wall are widespread anatomic anomalies of the human nose; they vary significantly in shape and location, and often cause the obstruction of the nasal airways. When severe, septal deviations need to be surgically corrected by ear-nose-throat (ENT) specialists. Septoplasty, however, has a low success rate, owing to the lack of suitable standardized clinical tools for assessing type and severity of obstructions, and for surgery planning. Moreover, the restoration of a perfectly straight septal wall is often impossible and possibly unnecessary. This paper introduces a procedure, based on advanced patient-specific Computational Fluid Dynamics (CFD) simulations, to support ENT surgeons in septoplasty planning. The method hinges upon the theory of adjoint-based optimization, and minimizes a cost function that indirectly accounts for viscous losses. A sensitivity map is computed on the mucosal wall to provide the surgeon with a simple quantification of how much tissue removal at each location would contribute to easing the obstruction. The optimization procedure is applied to three representative nasal anatomies, reconstructed from CT scans of patients affected by complex septal deviations. The computed sensitivity consistently identifies all the anomalies correctly. Virtual surgery, i.e. morphing of the anatomies according to the computed sensitivity, confirms that the characteristics of the nasal airflow improve significantly after small anatomy changes derived from adjoint-based optimization.

Impact of posture and CPAP on nasal airflow.

Obstructive sleep apnea (OSA) patients who use continuous positive airway pressure (CPAP) often complain of nasal dryness and nasal obstruction as side effects of CPAP. The physiological mechanisms by which CPAP may cause nasal dryness and nasal obstruction remain poorly understood. It has been hypothesized that CPAP interferes with the nasal cycle, abolishing the resting phase of the cycle and leading to nasal dryness. We performed rhinomanometry measurements in 31 OSA patients sitting, laid supine, and supine after 10 min of CPAP at 10 cmH2O. A posture change from sitting to supine led to more symmetric airflow partitioning between the left and right nostrils in the supine position. CPAP did not have a significant impact on nasal resistance, unilateral airflows, or airflow partitioning. Our results suggest that airflow partitioning becomes more symmetric immediately after changing to a supine position, while CPAP had no effect on nasal airflow, thus preserving the nearly symmetric airflow partitioning achieved after the posture change.

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.

Algorithm for Nasal Breathing Impairment Evaluation.

Assessing patients with complaints of nasal obstruction has traditionally been done by evaluation of the nasal airway looking for fixed or dynamic obstructive locations that could impair nasal airflow. Not infrequently, however, symptoms of nasal obstruction do not match the clinical examination of the nasal airway. Addressing this subset of patients may be a challenge to the surgeon. Evaluation of patients with symptoms of nasal obstruction should include a combination of a patient-reported assessment of nasal breathing and at least one objective method for measuring nasal airflow or nasal airway resistance or dimensions. This will allow distinction between patients with symptoms of nasal obstruction and low airflow or high nasal airway resistance and patients with similar symptoms but whose objective evaluation demonstrates normal nasal airflow or normal airway dimensions or resistance. Patients with low nasal airflow or high nasal airway resistance will require treatment to increase nasal airflow as a necessary step to improve symptoms, whereas patients with normal nasal airflow or nasal airway resistance will require a multidimensional assessment looking for less obvious causes of impaired nasal breathing sensation.

Overview of Nasal Airway and Nasal Breathing Evaluation.

Several methods are available for evaluating nasal breathing and nasal airflow, as this evaluation may be made from several different perspectives.Physiologic methods for nasal airway evaluation directly measure nasal airflow or nasal airway resistance, while anatomical methods measure nasal airway dimensions. Subjective methods evaluate nasal breathing through several validated patient-reported scales assessing nasal breathing. Computational fluid dynamics evaluates nasal airflow through the analysis of several physics' variables of the nasal airway.Being familiar to these methods is of utmost importance for the nasal surgeon to be able to understand data provided by the different methods and to be able to choose the combination of evaluation methods that will provide the information most relevant to each clinical situation.

Nasal Obstruction: Overview of Pathophysiology and Presentation of a Clinically Relevant Preoperative Plan for Rhino(Septo)plasty.

Impairment of nasal breathing is a highly prevalent and bothersome symptom that affects daily functioning and/or sleep quality. Those surgeons dealing with patients seeking rhinoplasty need to carefully analyze the preoperative nasal breathing capacity and predict the positive or even negative impact of rhino(septo)plasty on nasal breathing. Given the lack of correlation between the subjective feeling of suboptimal nasal breathing and the objective measurements of nasal flow and nasal resistance, a critical and mainly clinical evaluation of all anatomical, mucosal, and sensory mechanisms involved in nasal obstruction is mandatory. Indeed, thermo-, mechano-, and chemosensory receptors on the nasal mucosa, airflow, and respiratory dynamics might all contribute to the overall perception of nasal breathing capacity. In this review, we provide an overview of the factors determining suboptimal nasal breathing including different diagnostic and experimental tests that can be performed to evaluate nasal flow and nasal resistance and current limitations in our understanding of the problem of nasal breathing in an individual patient. An algorithm for the preoperative or diagnostic workup for nasal obstruction is included that might be useful as a guide for clinicians dealing with patients seeking nose surgery.

Peak Nasal Inspiratory Flow (PNIF) for Nasal Breathing Evaluation.

Measuring nasal airflow and nasal breathing has been a major goal of rhinology. Many objective methods for measuring nasal airflow or nasal airway resistance or dimensions provide valuable data but are time-consuming and require expensive equipment and trained technicians, thus making these methods less practical for clinical practice. Peak nasal inspiratory flow (PNIF) measurement is fast, unexpensive, noninvasive, and able to provide an objective evaluation of nasal airflow in real-time. Unilateral PNIF measurements allow separated evaluation of each side of the nasal airway and may prove particularly useful when clinical assessment detects significant asymmetry between both nasal cavities.PNIF measurements are most useful for assessing changes in nasal airflow achieved by any form of therapy, including surgical treatment of the nasal airway. These measurements generally correlate with other objective methods for nasal airway evaluation, but not unequivocally with patient-reported evaluation of nasal breathing. Nevertheless, as low PNIF values prevent the sensation of a suitable nasal breathing, PNIF measurement may also prove useful to optimize the decision of how to best address patients with complaints of nasal airway obstruction.

Analysis of conductive olfactory dysfunction using computational fluid dynamics.

Conductive olfactory dysfunction (COD) is caused by an obstruction in the nasal cavity and is characterized by changeable olfaction. COD can occur even when the olfactory cleft is anatomically normal, and therefore, the cause in these cases remains unclear. Herein, we used computational fluid dynamics to examine olfactory cleft airflow with a retrospective cohort study utilizing the cone beam computed tomography scan data of COD patients. By measuring nasal-nasopharynx pressure at maximum flow, we established a cut-off value at which nasal breathing can be differentiated from combined mouth breathing in COD patients. We found that increased nasal resistance led to mouth breathing and that the velocity and flow rate in the olfactory cleft at maximum flow were significantly reduced in COD patients with nasal breathing only compared to healthy olfactory subjects. In addition, we performed a detailed analysis of common morphological abnormalities associated with concha bullosa. Our study provides novel insights into the causes of COD, and therefore, it has important implications for surgical planning of COD, sleep apnea research, assessment of adenoid hyperplasia in children, and sports respiratory physiology.

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.

Computational Fluid Dynamics Modeling of Nasal Obstruction and Associations with Patient-Reported Outcomes.

BACKGROUND: Nasal obstruction is a common problem, with significant impact on quality of life. Accurate diagnosis may be challenging because of the complex and dynamic nature of the involved anatomy. Computational fluid dynamics modeling has the ability to identify specific anatomical defects, allowing for a targeted surgical approach. The goal of the current study is to better understand nasal obstruction as it pertains to disease-specific quality of life by way of a novel computational fluid dynamics model of nasal airflow. METHODS: Fifty-three patients with nasal obstruction underwent computational fluid dynamics modeling based on computed tomographic imaging. Nasal resistance was compared to demographic data and baseline subjective nasal patency based on Nasal Obstructive Symptom Evaluation scores. RESULTS: Mean Nasal Obstructive Symptom Evaluation score among all patients was 72.6. Nasal Obstructive Symptom Evaluation score demonstrated a significant association with nasal resistance in patients with static obstruction (p = 0.03). There was a positive correlation between Nasal Obstructive Symptom Evaluation score and nasal resistance in patients with static bilateral nasal obstruction (R2 = 0.32) and poor correlation in patients with dynamic bilateral obstruction caused by nasal valve collapse (R2 = 0.02). Patients with moderate and severe bilateral symptoms had significantly higher nasal resistance compared to those with unilateral symptoms (p = 0.048). CONCLUSIONS: Nasal obstruction is a multifactorial condition in most patients. This study shows correlation between simulated nasal resistance and Nasal Obstructive Symptom Evaluation score in a select group of patients. There is currently no standardized diagnostic algorithm or gold standard objective measure of nasal airflow; however, computational fluid dynamics may better inform treatment planning and surgical techniques on an individual basis. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, V.

Using thermal effect of 970 nm diode laser to reduce nasal swell body.

In recent decades, semiconductor lasers have been successfully used in rhinology. However, their usage in the reduction of the nasal swell body (NSB) is barely studied. Our research aimed to conduct an experimental selection of the laser exposure mode in the NSB zone using a 970 nm diode laser for safe and effective NSB reduction. The thermometric parameters of a diode laser with a wavelength of 970 nm were evaluated in a continuous contact mode of exposure at the power from 2 W to 10 W with 2 W step. The laser was targeted at the liver of cattle, given its similar optical properties to the NSB region. After a series of experiments with every power rate and the analysis of temperature data, we estimated an optimal exposure mode at a power of 4 W. The collected thermometric data demonstrate the safety of this mode in a clinical setting for NSB reduction due to causing no thermal damage to the adjacent tissue. Based on the experiment, a technique for laser reduction of the NSB was developed to improve nasal breathing in patients with severe hypertrophy of this area. The proposed technique was applied to 39 patients with chronic vasomotor rhinitis and the NSB. All patients were divided into 2 groups. Group 1 consisted of 20 patients who underwent surface contact laser-turbinectomy and the NSB reduction using a 970 nm diode laser. Group 2 included 19 patients with the same pathology who underwent laser-turbinectomy, without reduction of the NSB. No statistically significant difference was observed during the dynamic observation with an objective assessment of nasal respiration according to active anterior rhinomanometry when comparing these subgroups with each other according to the t-criterion for independent samples (p > 0.05). As a result of comparing the data obtained on the NOSE scale using the Student's t-test, a statistically significant difference is observed (p < 0.001). Thus, patients who did not perform the reduction of the NSB subjectively noted the insufficiency of nasal breathing. This fact indicates that the NSB is involved in the regulation of airflow.

Quick septoplasty in children: Long-term effects on nasal breathing and dentofacial morphology. A prospective cephalometric study.

OBJECTIVE: Many authors have investigated the most appropriate surgical approach to the deviated septum in childhood, considering the obligate mouth-breathing habit a possible cause of malocclusion and disharmonious development of the facial skeleton in growing kids. Nevertheless, controversies still remain about the long-term functional/esthetic results of such procedures, mainly due to the duration of the follow-up and possible confounding factors. METHODS: 111 Caucasian children (age range: 6-13 years) were submitted to a personal "Quick" septoplasty surgical technique between 2005 and 2010. Preoperative otorhinolaryngological examination using flexible nasal endoscopy, anterior active rhinomanometry (AAR), Nasal Obstruction Septoplasty Effectiveness (NOSE) questionnaire, and dentofacial evaluation (including cephalometry) were performed. Postoperative AAR, NOSE questionnaire and cephalometric assessment were carried out in all patients at the age of 18 years. Informed consent was obtained from children's parents as appropriate. RESULTS: No surgical complication was recorded. Among our patients, a significant (p <0.001) improvement of nasal breathing resistances at AAR and NOSE questionnaire scores was found after surgery. A significant improvement in cephalometric/dental parameters (gonial angle values, anterior facial height, prevalence of class I occlusion, maxillary intermolar width, and cross-bite frequency) was noticed after the follow-up with respect to preoperative conditions. CONCLUSION: The "Quick" septoplasty technique described is a practical and conservative procedure with a low complication rate that offers long-term favourable results for the correction of nasal septum deviations in children. Nasal-breathing restoration may favor a physiological and harmonious development of craniofacial and dental structures in offspring.

Objective measurement and patient-reported evaluation of the nasal airway: Is correlation dependent on symptoms or on nasal airflow?

BACKGROUND: Evidence has shown that the sensation of nasal breathing is related to variations in nasal mucosa temperature produced by airflow. An appropriate nasal airflow is necessary for changing mucosal temperature. Therefore, the correlation between objective measurements of nasal airflow and patient-reported evaluation of nasal breathing should be dependent on the level of nasal airflow. OBJECTIVES: To find if the correlation between patient-reported assessment of nasal breathing and objective measurement of nasal airflow is dependent on the severity of symptoms of nasal obstruction or on the level of nasal airflow. METHODS: The airway of 79 patients was evaluated using NOSE score and peak nasal inspiratory flow (PNIF). Three subgroups were created based on NOSE and three subgroups were created based on PNIF level to find if correlation was dependent on nasal symptoms or airflow. RESULTS: The mean value of PNIF for the 79 patients was 92.6 L/min (SD 28.1 L/min). The mean NOSE score was 48.4 (SD 24.4). The correlation between PNIF and NOSE was statistically significant (P = .03), but with a weak association between the two variables (r = -.248). Evaluation of correlation based on symptoms demonstrated a weak or very weak association in each subgroup (r = -.250, r = -.007, r = -.104). Evaluation of correlation based on nasal airflow demonstrated a very weak association for the subgroups with middle-level and high PNIF values (r = -.190, r = -.014), but a moderate association for the subgroup with low PNIF values (r = -.404). CONCLUSIONS: This study demonstrated a weak correlation between NOSE scores and PNIF values in patients non-selected according to symptoms of nasal obstruction or to airflow. It demonstrated that patients with symptoms of nasal obstruction have different levels of nasal airflow and that low nasal airflow prevents the sensation of good nasal breathing. Therefore, patients with symptoms of nasal obstruction may require improving nasal airflow to improve nasal breathing sensation.

Correlation between nasal mucosal temperature change and the perception of nasal patency: a literature review.

BACKGROUND: The mechanism of nasal airflow sensation is poorly understood. This study aimed to examine the role of nasal mucosal temperature change in the subjective perception of nasal patency and the methods by which it can be quantified. METHOD: Medline and PubMed database searches were performed to retrieve literature relevant to the topic. RESULTS: The primary mechanism producing the sensation of nasal patency is thought to be the activation of transient receptor potential melastatin family member 8 ('TRPM8'), a thermoreceptor that is activated by nasal mucosal cooling. Computational fluid dynamics studies have demonstrated that increased airflow and heat flux are correlated with better patient-reported outcome measure scores. Similarly, physical measurements of the nasal cavity using temperature probes have shown a correlation between lower nasal mucosal temperatures and better patient-reported outcome measure scores. CONCLUSION: Nasal mucosal temperature change may be correlated with the perception of improved nasal patency. Future research should quantify the impact of mucosal cooling on the perception of nasal airway obstruction.

The role of nasal congestion as a defence against respiratory viruses.

INTRODUCTION: This review discusses how nasal congestion may have benefits as a mechanism of defence against respiratory viruses. METHODS: A literature research was conducted on respiratory viruses and nasal congestion, following a recently published review on how temperature sensitivity is important for the success of common respiratory viruses. RESULTS: The literature reported that common respiratory viruses are temperature sensitive and replicate well at the cooler temperatures of the upper airways (32°C), but replication is restricted at body temperature (37°C). The amplitude of the phases of congestion and decongestion associated with the nasal cycle was increased on infection with respiratory viruses and this caused unilateral nasal congestion and obstruction. Nasal congestion and obstruction increase nasal mucosal temperature towards 37°C and therefore restricted the replication of respiratory viruses. CONCLUSION: Nasal congestion associated with the nasal cycle may act as a mechanism of respiratory defence against infection with respiratory viruses.

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

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

Nasal Peak Inspiratory Flow in Healthy and Obstructed Patients: Systematic Review and Meta-Analysis.

OBJECTIVES: Nasal peak inspiratory flow (NPIF) is a practical and affordable tool that measures maximum inspiratory flow rate through both nostrils. Although NPIF values for healthy controls and patients appear to differ considerably, a generally expected value for populations with and without nasal obstruction has yet to be established. The aim of this systematic review and meta-analysis was to determine the mean NPIF value in populations with and without nasal obstruction. METHODS: Medline (1946-) and Embase (1947-) were searched until July 1, 2017. A search strategy was used to identify studies that reported NPIF values for defined healthy or disease states. All studies providing original data were included. The study population was defined as having either normal nasal breathing or nasal obstruction. A meta-analysis of the mean data was presented in forest plots, and data were presented as mean (95% confidence interval [CI]). RESULTS: The search yielded 1,526 studies, of which 29 were included. The included studies involved 1,634 subjects with normal nasal breathing and 817 subjects with nasal obstruction. The mean NPIF value for populations with normal nasal breathing was 138.4 (95% CI: 127.9-148.8) L/min. The mean value for populations with nasal obstruction was 97.5 (95% CI: 86.1-108.8) L/min. CONCLUSIONS: Current evidence confirms a difference between mean NPIF values of populations with and without nasal obstruction. The mean value of subjects with no nasal obstruction is 138.4 L/min, and the mean value of nasally obstructed populations is 97.5 L/min. Prospective studies adopting a standardized procedure are required to further assess normative NPIF values. Laryngoscope, 131:260-267, 2021.

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.