The cause of nasal obstruction can often be attributed to pathologic conditions of the nasal valve. The key physical examination finding in nasal valve compromise is inspiratory collapse of the nasal sidewall. Validated subjective and objective measures evaluating nasal obstruction exist, although with weak correlation. Functional rhinoplasty encompasses the surgical techniques used to address obstruction occurring in this area. These techniques aim to increase the size of the nasal valve opening and/or strengthen the lateral nasal wall and nasal ala, preventing dynamic collapse. Much of the supporting evidence for functional rhinoplasty consists of observational studies that are universally favorable.
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Subjective patient-reported measures have an important role in the evaluation of nasal obstruction. Of these measures, the Nasal Obstruction Symptom Evaluation and visual analog scales are the most applicable to nasal valve compromise (NVC).
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Several objective measures for nasal obstruction exist, although none of them are widely accepted as the gold standard. New methods for evaluating nasal physiology, such as computational fluid dynamics, may prove valuable in the evaluation and treatment of NVC.
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In general, there is weak correlation between existing subjective and objective measures of nasal obstruction and controversy over which are most important in evaluating the efficacy of treatment.
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Surgical treatment of NVC consists of a wide variety of techniques, with evidence for their efficacy, although better study designs and outcome measures are needed.
Problem/overview
Nasal obstruction is a complaint frequently encountered in otolaryngology. This obstruction can occur as a result of underlying inflammatory or anatomic pathologic conditions. Inflammatory pathologic conditions include allergic rhinitis, nasal polyposis, and chronic rhinosinusitis. Among the anatomic causes are septal deviation, turbinate hypertrophy, and nasal valve compromise (NVC). The nasal valve was first described by Mink in the early twentieth century but has received increasing attention recently. It is the narrowest portion of the nasal airway and, therefore, where the most resistance to airflow occurs. It can be divided into external and internal portions ( Fig. 1 ). The external nasal valve is the area in the nasal vestibule formed by the alar rim, nasal sill, caudal septum, and medial crus of the lower lateral cartilage. The internal nasal valve is the area bound by the caudal edge of the upper lateral cartilage, nasal septum, head of the inferior turbinate, and nasal sill ( Fig. 2 ) and is located approximately 1.3 cm from the nares. It is proposed that the nasal valve serves as a regulator to prevent airflow from exceeding the capacity of the nose to warm and humidify inspired air.
Problems with nasal airflow occurring at the nasal valve exhibit both static and dynamic properties. There can be fixed anatomic obstruction caused by abnormalities of any of the structures that contribute to the makeup of the nasal valve, including the septum, turbinates, and nasal cartilages. These abnormalities can exist as a result of traumatic, congenital, or iatrogenic causes. There can also be a dynamic component to NVC. Bernoulli’s principle states that air flowing into narrowed segments accelerates, leading to a decrease in intraluminal pressure. This phenomenon can contribute to dynamic collapse of the lateral nasal wall during inspiration, leading to further compromise of the nasal valve region resulting in obstruction of nasal airflow. The difficulty in evaluating patients with NVC is determining whether the problem is the small diameter of the nasal valve causing fixed obstruction or whether the lack of rigidity of the lateral nasal wall leading to dynamic collapse is the issue because the surgical approach may differ depending on the underlying problem.
Functional rhinoplasty has emerged in the literature as a collective term for procedures that address nasal obstruction occurring at the nasal valve. This term serves to differentiate procedures directed at correcting nasal obstruction from those that address the cosmetic appearance of the nose and includes techniques that target the nasal septum (dorsal and caudal portions), lateral nasal wall, and the soft tissue nasal vestibule. However, in reality, the structure and function of the nose are intimately related. Therefore, procedures performed with the intent to change the cosmetic appearance of the nose can also affect its function and vice versa. One must be cognizant of this relationship when counseling patients and undertaking nasal surgery for either cosmetic or functional purposes. Functional rhinoplasty and nasal valve repair are commonly used as synonymous terms and, thus, are used interchangeably for the purposes of this article.
Evidence-based clinical assessment
History and Physical Examination
The main symptom of NVC is decreased nasal airflow. However, there are a myriad of conditions that can present with nasal obstruction. These conditions include infectious, inflammatory, and neoplastic conditions, and the treatment varies depending on the underlying cause. Therefore, a detailed history should include the timing, onset, seasonal variation, laterality, prior history of nasal trauma or surgery, and exacerbating or alleviating factors of nasal obstruction. It is also important to determine the presence or absence of associated symptoms, such as epistaxis, anosmia, rhinorrhea, or postnasal drainage. This differentiation can help identify or rule out causes of nasal obstruction that are not attributable to pathologic conditions of the nasal valve.
There is currently no gold standard objective test to diagnose NVC ; it remains a clinical diagnosis. A general assessment of the external appearance of the nose can identify problems with the potential to cause nasal obstruction, such as nasal tip ptosis, a narrow midvault, an inverted-V deformity, or narrowed nostrils. Additional physical examination techniques can identify abnormalities of the lateral nasal wall related to weak or malformed upper and/or lower lateral cartilages. Specifically, findings on physical examination suggestive of NVC include visible inspiratory collapse of the lateral nasal wall or alar rim. Also, subjective and audible improvement in nasal airflow during a Cottle maneuver (lateral retraction of the cheek) or modified Cottle maneuver (intranasal lateralization of the lateral nasal wall) is consistent with NVC.
Anterior rhinoscopy is an adequate intranasal evaluation of the nasal valve region and will provide information about the position of the septum and size of the turbinates. Nasal endoscopy can be useful to rule out other causes of nasal obstruction not attributable to NVC if the diagnosis is uncertain but is not routinely indicated. If surgery is being planned or considered, preoperative photography can be helpful for patient counseling, preoperative planning, and documentation, even in cases when the surgical intent is purely functional, but this is especially true if surgery is being undertaken for both functional and cosmetic purposes.
In patients with NVC, it can be difficult to determine which components of the nasal valve to address because there are several anatomic structures that contribute. However, identifying the problematic area can help guide the surgeon in deciding which procedure is likely to provide the most benefit. In general, functional rhinoplasty techniques target a specific area or component of the nasal valve. Also, determining whether obstruction is resulting more from fixed or dynamic obstruction can help the surgeon decide between a procedure intended to increase the actual diameter of the nasal valve or one that aims to strengthen a weak lateral wall or alar rim.
Subjective Measures of Nasal Obstruction
Traditionally, a common method of assessing nasal obstruction and reporting outcomes of functional nasal surgery is subjective patient-reported measures. For assessing the efficacy of a surgical intervention, a comparison of preoperative and postoperative results is often used. In addition, there has been a trend in medicine toward evaluating quality of life (QOL) in the assessment of disease processes and the efficacy of treatment. Generic health-related QOL can be measured using scales, such as the Medical Outcomes Study Short Forms (SF-12 and SF-36). However, disease-specific QOL measures can be superior to generic QOL instruments because they may be more sensitive for the detection and quantification of small changes. There are validated QOL instruments specific for rhinologic disease, such as the Rhinosinusitis Disability Index, Rhinoconjunctivitis Quality of Life Questionnaire, and the Sinonasal Outcomes Test, each of which has been used in the past for evaluating septal or nasal valve pathologic conditions. These instruments all include nasal obstruction in their evaluation; however, their primary purpose is the evaluation of inflammatory nasal disease, which may secondarily result in nasal obstructive symptoms.
Nasal obstruction symptom evaluation scale
The QOL measure most relevant to structurally based nasal valve pathologic conditions is the Nasal Obstruction Symptom Evaluation scale, a disease-specific quality-of-life instrument developed for the assessment of nasal obstruction with evidence in support of its validity, reliability, and sensitivity. With this instrument, patients are asked to rate the severity of several nasal symptoms and the results are summed and scaled. Its original use was in patients undergoing septoplasty who demonstrated an improvement in disease-specific QOL after surgery. Subsequent studies using the NOSE scale in patients undergoing surgery for NVC also demonstrated statistically significant improvements in disease-specific QOL.
Visual analog scales
Visual analog scales (VAS) are a common method of subjectively measuring symptoms in various conditions that have also been used as an evaluation method and outcome measure in nasal obstruction. In VAS, patients are asked to rate their experience of symptoms on a linear scale ranging from no obstruction to complete obstruction. Multiple studies have shown improvement in VAS for nasal obstruction after nasal valve repair. One potential advantage of VAS over other objective tests is that, for patients with unilateral symptoms, VAS for each side of the nasal cavity can be assessed separately. Several studies show better correlation between VAS for nasal obstruction and objective measurement techniques when unilateral VAS is used.
Objective Measures of Nasal Obstruction
Aside from subjective measures, there is also interest in the development and implementation of validated objective measures to assist in preoperative evaluation and to better assess surgical outcomes. Several techniques have been developed and validated to date. Of these, rhinomanometry and acoustic rhinometry (AR) have been used most frequently. Rhinomanometry allows the determination of nasal airway resistance by simultaneously measuring transnasal pressure drop and nasal airflow. This technique has been used to objectively document changes in nasal resistance after nasal valve surgery. However, it is not in widespread use because of several limitations. These drawbacks include the inability to precisely locate the area of obstruction and the need for specialized equipment and a well-trained operator.
AR for nasal obstruction
AR is a technique that uses the measurement of deflected sound waves to provide an estimate of the cross-sectional area (CSA) of the nasal cavity as a function of the distance from the nostrils. AR is relatively easy to perform and is quick and noninvasive. It too has limitations, however. Similar to rhinomanometry, it does require specialized equipment and an experienced operator. Also, the results obtained are sensitive to variations in technique and testing conditions. Another known limitation of AR is that it overestimates CSA in areas beyond 5 cm from the nostrils or after constricted regions or areas of drastic changes in nasal anatomy. The advantages of AR make it one of the most common objective methods used to evaluate nasal patency. However, it has not achieved widespread clinical use because of the limitations noted previously.
Imaging studies for nasal obstruction
Imaging studies, such as computed tomography (CT) or magnetic resonance imaging (MRI) scans, can have a role in the evaluation of nasal obstruction, with utility in evaluating infectious, inflammatory, or neoplastic disease, but have a limited role in the evaluation of nasal valve pathologic conditions specifically. CT imaging can be used as a method of measuring the nasal valve angle (between the septum and upper lateral cartilage). When used for this purpose, the most accurate measures are obtained from views other than the traditional coronal view, which may underestimate the true nasal valve angle. Specifically, a modified view known as the nasal base view, which uses slices oriented perpendicular to the approximated acoustic axis of the nose, provides the most accurate information about the nasal valve angle. This technique has not been adopted for widespread use because there is subjectivity in the selection of the acoustic axis and the need to reformat CT images into a nonstandard view. There is also a lack of evidence in regard to its reproducibility, although studies comparing this method with AR-derived data show good correlation in the measurement of the nasal valve area.
Computational fluid dynamics for nasal obstruction
Computational fluid dynamics (CFD) is emerging as a new method to evaluate nasal airflow and resistance as well as other physiologic parameters important to the function of the nose, including particle deposition and air conditioning. CFD is a technology used widely in engineering as a way to model the motion of fluids. For this technique, anatomically accurate 3-dimensional computational models of patients’ nasal cavities are generated from imaging data captured by CT or MRI ( Fig. 3 ). CFD software programs can then be used to obtain computed measures of airflow, resistance, heat transfer, and air humidification.
The ability to study multiple parameters of interest under different simulated conditions with minimal cost or inconvenience to patients makes CFD an attractive method to investigate nasal function. A further benefit of CFD over other objective measures of nasal function is the ability to determine airflow and other factors of interest at precise anatomic locations rather than in the nasal cavity as a whole as is done with other methods. Another exciting extension of CFD technology is the ability to do simulated surgery on the digital models. The computed nasal geometry can be virtually modified in a manner reflecting surgical techniques, and, subsequently, new patterns of airflow and heat and water vapor transport can be calculated.
There are also limitations with current CFD technology. There is additional cost to obtain the necessary imaging studies. Also, at present, the process of producing the digital models is time and labor intensive, although as technology has advanced, the cost and time to build models has declined and is expected to continue to do so. Further, although models can be built from either CT or MRI scans, the models based on CT imaging give better results because of better resolution, thus subjecting patients to radiation exposure that they would otherwise not receive. CFD also makes assumptions that are reasonable in many cases but may not always hold true, such as laminar flow of air within the nasal cavity, fixed and rigid nasal cavity walls, and steady-state airflow.
CFD analysis with respect to nasal function is still in its early stages and most studies are limited in scope and number. Further studies are needed to fully validate the method and elucidate the correlation between CFD-derived parameters and actual clinical and patient-reported data. However, this exciting technology holds great promise and may prove to be a valuable resource in objective preoperative evaluation, surgical planning, and analysis of surgical outcomes for surgeons performing functional rhinoplasty.
Controversy in Outcome Measures
An area of conflict in many medical conditions is the relationship between what patients subjectively report and what is objectively observed by physicians or measured by objective tests. This point is especially true in the area of nasal obstruction. This issue is complex and is not explained by nasal resistance and airflow alone. Nasal sensation also plays a large role, as demonstrated by studies whereby nasal sensation has been blocked with local anesthetics in the nasal cavity or vestibule, with studies reporting both increases and decreases in perceived nasal airflow without any measured effect on nasal resistance. This finding suggests that the sensation of nasal airflow may, under certain circumstances, be independent of any objectively measurable change in nasal resistance. Therefore, some investigators have made the argument that subjective patient-reported measures are the most important factor when evaluating nasal obstruction.
Ideally, a gold standard objective test would be quantifiable, reproducible, and have a strong correlation with subjective measures of nasal airflow. As described earlier, such a test has not been reported to date. Independently, subjective and objective tests have shown validity and reproducibility but there is weak correlation when compared side by side. It has been proposed that the different methods of assessment are capturing different aspects of the nasal airway and, therefore, may be complementary. Although an ideal test of nasal patency remains elusive, it may prove to be the case in the future that a combination of testing methods with both subjective and objective components best approaches the conditions mentioned earlier. In the meantime, the debate is ongoing regarding the role of subjective and objective measures in the evaluation of nasal obstruction.
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