Nasal obstruction among patients who have chronic rhinosinusitis

Nasal obstruction is the most common and severe complaint among patients who have chronic rhinosinusitis (CRS). The prevalence of nasal obstruction among patients undergoing functional endoscopic sinus surgery (FESS) for CRS is reported to be between 83.5% and 98%. When assessing individual symptoms of CRS, nasal obstruction often ranks highest in patient-reported symptom severity. Furthermore, patients who have CRS with nasal polyposis seem to have a statistically higher incidence of nasal obstruction when compared with patients without nasal polyposis.

Consequently, nasal obstruction is one of six major symptom criteria adopted by the 2003 American Academy of Otolaryngology–Head and Neck Surgery (AAOHNS) Rhinosinusitis Task Force (RSTF) for the diagnosis of CRS. In their recent update, the 2007 AAOHNS sinusitis practice guideline continued to identify nasal obstruction as one of the major symptom criteria used to diagnose CRS with high sensitivity. Given its prevalence in patients who have CRS, it also constitutes one of the specific symptoms evaluated by validated instruments developed to measure disease-specific symptoms in CRS, including the Rhinosinusitis Symptom Inventory (RSI) and the Chronic Sinusitis Survey (CSS).

Although studies comparing objective or subjective assessments of nasal obstruction in patients who have CRS with those of matched normal controls are still lacking, studies demonstrate subjective and objective improvements in patients who have CRS after medical and surgical therapy.

Sensation of nasal airflow

The mechanisms used by the nasal airway to perceive nasal airflow still remain under investigation. The sensation of airflow is thought to be mediated by tactile and thermoreceptors located in the skin of the nasal vestibule and the mucosa of the nasal cavum. The sensitivity of these receptors has been shown to decrease in an anterior-to-posterior direction, with a minimum detected airflow velocity of 6.5 ms ⁻¹ at the nasal vestibule and 19.2 ms ⁻¹ in the posterior nose. These receptors are thought to originate from ophthalmic and maxillary branches of the trigeminal nerve, because topical anesthesia of these branches results in the sensation of nasal obstruction.

Although the exact receptor for nasal airflow sensation is still unknown, the effect of menthol or other volatile oils provides us with some insight on the molecular events that mediate the ability to perceive nasal airflow. When applied to the nose, menthol causes a well-known cooling sensation resulting in the perception of decongestion. This perception does not correlate with an increase in nasal airflow or a decrease in total nasal airway resistance (TNAR). The mechanism of menthol’s action on thermoreceptors was recently elucidated by two independent studies, which showed that menthol’s cooling effect was mediated by its being an agonist for TRPM8—a cool, temperature-activated, cationic channel.

Sensation of nasal airflow

The mechanisms used by the nasal airway to perceive nasal airflow still remain under investigation. The sensation of airflow is thought to be mediated by tactile and thermoreceptors located in the skin of the nasal vestibule and the mucosa of the nasal cavum. The sensitivity of these receptors has been shown to decrease in an anterior-to-posterior direction, with a minimum detected airflow velocity of 6.5 ms ⁻¹ at the nasal vestibule and 19.2 ms ⁻¹ in the posterior nose. These receptors are thought to originate from ophthalmic and maxillary branches of the trigeminal nerve, because topical anesthesia of these branches results in the sensation of nasal obstruction.

Although the exact receptor for nasal airflow sensation is still unknown, the effect of menthol or other volatile oils provides us with some insight on the molecular events that mediate the ability to perceive nasal airflow. When applied to the nose, menthol causes a well-known cooling sensation resulting in the perception of decongestion. This perception does not correlate with an increase in nasal airflow or a decrease in total nasal airway resistance (TNAR). The mechanism of menthol’s action on thermoreceptors was recently elucidated by two independent studies, which showed that menthol’s cooling effect was mediated by its being an agonist for TRPM8—a cool, temperature-activated, cationic channel.

Measuring nasal obstruction

Rhinomanometry is the traditional method for measuring nasal airway resistance and nasal patency. This invasive technique requires simultaneous pressure measurements in the anterior and posterior parts of the nasal airway so as to calculate a transnasal pressure gradient. The ratio of the transnasal pressure gradient and the measured rate of nasal airflow allows an estimate of the TNAR. Among normal subjects, total resistance of the nasal passage has been reported, with a range of 0.15 to 0.39 Pa/cc/s. The major limitation of rhinomanometry is its inability to measure nasal resistance in instances of total nasal obstruction.

Acoustic rhinometry uses reflected sound waves to calculate the patent cross-sectional area at any point in the nasal passage to identify anatomically obstructed portions of the nasal airway. Because the cross-sectional area of any point within the nasal airway can be measured, the summation of these individual slices can be used to calculate a total nasal cavity volume. These measures of cross-sectional area and total nasal cavity volume have been validated against other anatomic measures, such CT, MRI, and nasal endoscopy. Given the correlation between acoustic rhinometry and these various imaging modalities, CT- and MRI-generated measurements of patent nasal airway have also been advocated as means of noninvasively evaluating the patency of the nasal airway.

Nasal spirometry, typically reported as the nasal inspiratory peak flow (NIPF) rate, provides a noninvasive physiologic measure of nasal patency by asking patients to inspire forcefully while attached to a specially designed nasal flow meter mask. The peak airflow achieved is measured in liters per minute and has been validated against rhinomanometry as a valid measure of nasal patency.

Correlation between objective measurements of nasal patency and patient-reported nasal obstruction

Unfortunately, objective measurements of nasal obstruction and patient-reported symptoms of nasal obstruction correlate poorly. A study of 250 subjects compared TNAR, as determined by rhinomanometry, with assessments of total nasal obstruction, as reported by a visual analog scale (VAS) and failed to show any correlation between the two parameters. Conversely, rhinomanometric studies investigating unilateral nasal resistance in 60 participants who had the common cold found that patients could correctly identify acute unilateral nasal obstruction in approximately 77% of cases. When the level of airflow asymmetry exceeded 100 cm /s, the same study found that a subject’s ability to identify the more obstructed side increased to 95%. The investigators concluded that subjects would be unable to discriminate unilateral nasal obstruction if the airflow difference was less than 50 cm ³ /s.

Recently, Kjaergaard and colleagues reported a cross-sectional study evaluating 2523 consecutive otolaryngology patients using acoustic rhinometry and peak nasal inspiratory flow and correlated these measurements with subject-reported nasal obstruction. This study found that the minimum cross-sectional area of the posterior and entire nasal passage, the nasal cavity volume of the anterior and posterior nasal passage, and the peak nasal inspiratory flow rate were significantly correlated with subject VAS-reported ratings of nasal obstruction. Interestingly, the study showed that the minimum cross-sectional area of the anterior nasal passage (defined in this study as the first 3 cm of the nasal cavity), which includes the nasal vestibule and nasal valve, was not significantly correlated with the sensation of nasal obstruction. Unlike the findings of this study, a separate investigation prospectively examined 290 nonrhinologic patients using similar subjective and objective measures of a VAS, acoustic rhinometry, and peak nasal inspiratory flow and failed to show any significant correlation between objective and subjective measures of nasal obstruction.

Together, these findings suggest that despite the high sensitivity of receptors located within the nasal vestibule, narrowing within the region of the nasal airway containing the turbinates results in a higher perception of nasal obstruction. Perhaps the formation of a functional nasal valve outside the anticipated position in the anterior nasal cavity results in a perception of nasal obstruction. Another theme seems to be that studies consisting of predominantly rhinologic patients show better correlation between perceived and objectively measured nasal obstruction than those examining normal subjects. Hence, by inference, the presence of obstruction induced by pathologic findings, such as CRS, would heighten the perceptibility of nasal obstruction. These findings highlight the challenges in designing and analyzing studies examining nasal obstruction before and after FESS.

Influence of functional endoscopic sinus surgery on patient-reported nasal obstruction

After treatment with maximal medical therapy, FESS is the preferred modality of treatment for refractory CRS. Although nasal obstruction is one of the most prevalent and severe symptoms of CRS, it was specifically studied in only 42% of the 131 FESS outcome studies identified in an extensive search of English-language studies including 10 or more patients. The studies examining patient-reported changes in nasal obstruction also show significant variability in study design, ranging from retrospective patient experiences after surgery to prospectively recruited patient cohorts with pre- and postsurgical questionnaires. Some of the patient-reported symptom-specific data use validated measures, such as patient reported pre- and postoperative VAS scoring and Likert scale scoring. Table 1 summarizes some of the studies that specifically address the symptom of nasal obstruction in assessing outcomes after FESS.

Several retrospective studies have examined outcomes after FESS with specific attention paid to patient-reported symptoms of nasal obstruction. In a study published in 1992, Kennedy reported on the outcomes in 120 patients who had inflammatory sinus disease, with a mean follow-up of 1.5 years; subsequently, Senior and colleagues reported outcomes of the same cohort at 7.8 years. This cohort was surveyed after surgery using categoric responses, with patients asked to estimate the level of improvement of nasal obstruction after endoscopic sinus surgery (eg, improvement of 25%, 50%, 75%, or 100%). Their responses in the dimension of nasal obstruction indicated an average of 66% improvement at 1.5 years after surgery and 65% improvement at 7.8 years after surgery. The overall percentage of patients reporting some improvement after surgery at 7.8 years after surgery was 97.1%. These results were generally supported in a study by Chambers and colleagues, which showed a similar large improvement in subjective nasal obstruction.

To address the inherent problems of retrospective data, several prospective studies have since evaluated the effectiveness of FESS in relieving symptoms specific to CRS. Bhattacharyya ¹ prospectively examined 100 consecutive adult patients undergoing primary FESS with mean follow-up at 12.4 months and showed that post-FESS nasal obstruction severity decreased by the largest magnitude when compared with all other symptoms in the RSTF diagnostic criteria. The effectiveness of FESS on relieving patient-reported nasal obstruction persisted in a separate group of 21 patients who underwent revision FESS for refractory disease. A separate study involving 82 prospectively enrolled patients demonstrated that the relief of nasal obstruction was durable at 3 years after surgery. These researchers noted that patients with Samter’s triad had significantly more nasal obstruction at their 24-month and 36-month follow-ups.

More recently, Damm and colleagues prospectively evaluated the impact of FESS on CRS-specific symptoms using pre-FESS and post-FESS questionnaires utilizing a Likert-scale like instrument (eg, 0 [no symptoms]–4 [intolerable]) that was completed by the 279 patients in their study. At a mean follow-up of 31.7 months, patients reported that their nasal obstruction severity had decreased from a mean score of 2.8 to a mean score of 0.59 ( P <.001). When compared with patient-reported overall quality of life (QOL), improvement in nasal obstruction showed the highest correlation with increased QOL ( r = 0.59) compared with the other symptom parameters evaluated in this study. A separate study by Ling and Kountakis examined this issue of symptom correlation to QOL using VAS-reported RSTF symptom criteria to evaluate its relation to the Sinonasal Outcome Test-20 (SNOT-20), a validated broader measure that summarizes disease-specific symptoms and QOL into a single mean item score. At 1 year after FESS for CRS, their study involving 158 patients showed that postsurgical nasal obstruction decreased in prevalence (20.9% versus 83.5%) and severity (0.4 versus 5.9) on VAS-reported nasal obstruction when compared with preoperative scores. Unlike the findings of Damm and colleagues, however, the RSTF reported that scores failed to correlate with the SNOT-20, which includes measures of overall QOL.

Soler and colleagues published a series of 279 prospectively enrolled patients with a comprehensive evaluation of individual patient symptoms before surgery and with detailed postoperative follow-up to 18 months. Their study once again reiterated the high prevalence and severity of nasal obstruction among their patients, while also identifying nasal congestion as one of the most disabling aspects of CRS after headache and facial pain. Their study demonstrated significant and durable relief of nasal obstruction after FESS, but their results also suggested that the relief from nasal obstruction was maximal 3 months after surgery and tended to increase slowly with time.

In an effort to compare medical and surgical management of CRS, Ragab and colleagues prospectively randomized 90 patients who had failed medical therapy consisting of nasal douching and a nasal steroid spray to FESS or further medical therapy consisting of low-dose macrolide therapy, intranasal or oral steroid therapy, and nasal douching. Although specific data are not provided in the report of this study, these investigators state that nasal obstruction was specifically studied as a parameter and that significant ( P <.01) reductions were noted in the medical and surgical groups. With the sample size in their study, no significant differences were noted comparing nasal obstruction in patients managed using medical or surgical therapy.