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Background
There are many potential causes for nasal obstruction. Some of the most common causes are allergic rhinitis, deviation of the nasal septum, or sinus or nasal infection. Nasal obstruction is typically diagnosed by a patient’s subjective complaint of nasal stuffiness coupled with a physical examination demonstrating anatomic restriction of the nasal passages.
Rhinomanometry and acoustic rhinometry are objective tests that have been attempted to assess nasal airway patency. Rhinomanometry measures air pressure and the rate of airflow during breathing. These measurements are then used to calculate nasal airway resistance. Acoustic rhinometry uses a reflected sound signal to measure the cross-sectional area and volume of the nasal passage. Acoustic rhinometry gives an anatomic description of a nasal passage, whereas rhinomanometry gives a functional measure of the pressure/flow relationships during the respiratory cycle. Both techniques have been used in comparing decongestive action of antihistamines and corticosteroids and for assessment of an individual prior to or following nasal surgery.
Some investigators have found that subjective symptoms as rated by patients frequently do not correlate with rhinomanometry and acoustic rhinometry measurements (Passali et al, 2000). In addition, significant symptoms can be present without airway restriction (e.g., in patients with atrophic mucosa or sinusitis). In a clinical trial (n = 49) on the role of acoustic rhinometry in the diagnosis of adenoidal hypertrophy, Riechelmann et al (1999) reported that acoustic rhinometry, in general, is not suitable for assessing adenoidal size in pre-school children. He found that acoustic rhinometry was not able to differentiate controls from symptomatic children admitted for adenoidectomy.
Pallanch et al (1998) stated that there are many objective test values where some patients will complain of obstruction but others will not. It follows that there is not a single population threshold for the airway at which symptomatic obstruction would occur. Instead, it appears that there is a range of individual threshold values. Thus, it is not always possible to identify who will feel obstructed based on airway data.
There is inadequate evidence of the clinical utility of rhinomanometry and acoustic rhinometry. These tests have not been demonstrated to be superior to physical examination, nasal endoscopy or CT imaging in selecting patients who would benefit from medical and/or surgical management of their nasal obstruction. Clinical studies published in the peer-reviewed medical literature are necessary to determine the value of rhinomanometry and acoustic rhinometry in the diagnosis and clinical management of patients with nasal obstruction.
Tarhan et al (2005) compared acoustic rhinometry (AR) data to CT data to evaluate the accuracy of AR measurements in estimating nasal passage area and evaluated its ability of quantifying paranasal sinus volume and ostium size in live humans. Twenty nasal passages of 10 healthy adults were examined by using AR and CT. Actual cross-sectional areas of the nasal cavity, sinus ostia sizes, and maxillary and frontal sinus volumes were determined from CT sections perpendicular to the curved acoustic axis of the nasal passage. Nasal cavity volume (from nostril to choana) calculated from the AR-derived area-distance curve was compared with that from the CT-derived area-distance curve. AR measurements were also done on pipe models that featured a side branch (Helmholtz resonator of constant volume but 2 different neck diameters) simulating a paranasal sinus. In the anterior nasal cavity, there was good agreement between the cross-sectional areas determined by AR and CT. However, posterior to the sinus ostia, AR over-estimated cross-sectional area. The difference between AR nasal volume and CT nasal volume was much smaller than the combined volume of the maxillary and frontal sinuses. The results suggested that AR measurements of the healthy adult nasal cavity are reasonably accurate to the level of the paranasal sinus ostia. Beyond this point, AR over-estimates cross-sectional area and provides no quantitative data for sinus volume or ostium size. The effects of paranasal sinuses and acoustic resonances in the nasal cavity are not accounted for in the present AR algorithms.
Cakmak et al (2005) evaluated how anatomic variations of the nasal cavity affect the accuracy of AR measurements. A cast model of a human nasal cavity was used to examine the effects of the nasal valve and paranasal sinuses on AR measurements. A luminal impression of a cadaver nasal cavity was made, and a cast model was created from this impression. To simulate the nasal valve, inserts of varying inner diameter were placed in the model nasal passage. To simulate the paranasal sinuses, side branches with varying neck diameters and cavity volumes were attached to the model. The AR measurements of the anterior nasal passage were reasonably precise when the passage area of the insert was within the normal range. When the passage area of the insert was reduced, AR measurements significantly under-estimated the cross-sectional areas beyond the insert. The volume of the paranasal sinus had limited effect on AR measurements when the sinus ostium was small. However, when the ostium size was large, increasing the volume of the sinus led to significant over-estimation of AR-derived areas beyond the ostium. The authors concluded that the pathologies that narrow the anterior nasal passage result in the most significant AR error by causing area under-estimation beyond the constriction. It also appears that increased paranasal sinus volume causes over-estimation of areas posterior to the sinus ostium when the ostium size is large. If these physical effects are not considered, the results obtained during clinical examination with AR may be misinterpreted.
Liu et al (2006) examined the association between AR findings and results of over-night polysomongraphy. Patients who were under the age of 20 years, had severe deviated nasal septum, had previously received nasal or palatal surgery, or could not complete sleep test or AR examination were excluded. Subjects' basic data including age, gender, neck circumference, and body mass index (BMI) were collected. All participants received AR before over-night polysomnography. The results along with sleep-test outcomes were recorded and analyzed. A total of 87 patients were included in this study. Patients with respiratory disturbance index (RDI) less than 5/hour (n = 26) or with RDI of 5 - 30/hour (n = 28) tended to have larger minimal cross-sectional area (MCA) compared with those of patients whose RDI was more than 30/hour (n = 33) (p = 0.001). A stepwise multiple regression analysis showed that BMI, male gender, and MCA were contributing factors in RDI. The R2 value of the multiple regression analysis was 0.406. The authors concluded that patients with severe obstructive sleep apnea tended to have smaller MCA when compared with patients with RDI less than 30/hour. However, it was hard to predict whether patients had obstructive sleep apnea from AR examination.
Bermüller and colleagues (2008) examined the diagnostic accuracy of rhinomanometry (RMM) and peak nasal inspiratory flow (PNIF) in functional rhinosurgery. Measurements were carried out on 40 healthy individuals and 53 patients with symptomatic nasal stenosis. Cut-offs for RMM and PNIF were defined by receiver operating characteristic analysis. A cut-off between normal and pathological of 700 ml/second for RMM at a trans-nasal pressure difference of 150 Pa, and of 2,000 ml/second (120 L/minute) for PNIF was calculated. No significant differences in terms of sensitivity of RMM and PNIF (0.77 versus 0.66), specificity (0.8 versus 0.8) and diagnostic accuracy (0.79 versus 0.72) were found. The authors concluded that RMM and PNIF provide valuable information to support clinical decision making. However, with bothe methods, about 25 % of symptomatic patients with functionally relevant nasal structural deformity were not detected. Furthermore, a negative test outcome of RMM or PNIF does not exclude a functionally relevant nasal stenosis.
Straszek and associates (2008) stated that despite a growing number of studies using AR in children, no reference material exists that incorporates the entire age and height interval of pre-school children up to puberty for a range of rhinometric variables. These researchers attempted to provide a reference range for nasal volumes and MCAs in healthy non-decongested children aged 4 to 13 years old. A total of 256 primary school children (mean age of 7.95 years; range of 3.8 to 13.1 years; 123 boys/133 girls) were measured by AR. Variables were MCA (first, second, and absolute minimum) and nasal volumes from 0 to 4 cm (Vol0-4), 0 to 5 cm (Vol0-5), 1 to 4 cm (Vol1-4), and 2 to 5 cm (Vol2-5) into the nasal cavity. Height and weight were measured and atopic status was determined by skin-prick test. Age as well as current and past respiratory health were recorded from a questionnaire. In multiple linear regression models, height was the main predictor for all AR variables although weight also was a significant predictor of MCAs. There was no association between any AR variables with sex, atopy, or hay fever; but children with current wheeze (within last 12 months) and asthma had decreased nasal patency. The authors concluded that this study presented the most extensive current reference material for AR in non-decongested pre-pubescent healthy children. They stated that the presented reference material will aid the interpretation and evaluation of future and present epidemiological studies based on AR in children.
Piszcz et al (2008) reported on the use AR in assessing nasal obstruction due to adenoid hypertrophy in patients referred for adenoidectomy; they also evaluated on changes in the volume of the nasopharynx after adenoidectomy. The examination was performed in patients (n = 30) aged 5 to 10 years with adenoid hypertrophy admitted for adenoidectomy. Ten children who are free of otolaryngological problems served as the control group. All subjects had AR performed and additionally, endoscopic method such as rhynofiberoscopy and endoscopy of nasopharyngs were introduced in the patient's group. The study showed that children with adenoid hypertrophy have statistically significant reduction of nasopharyngeal volume (NPV) versus the control group. Adenoidectomy increases the NPV parameter and makes it equal to control group. The authors concluded that AR seems to be a promising method in the assessment of nasopharyngeal volume. They noted that this and further studies may help to reduce the number of "unnecessary" adenoidectomies, by making standards for NPV in different group of age.
Okun and colleagues (2010) evaluated the use of AR in children with obstructive sleep apnea (OSA). Subjects with clinically suspected OSA underwent AR measurements followed by attended over-night polysomnography. Of a total of 20 subjects (13 boys, 7 girls), 15 (75 %) had OSA, defined as apnea-hypopnea index (AHI) greater than or equal to 5 events per hour of sleep, and 5 had primary snoring (PS). The mean AHI was 16.79 versus 1.96 events/hour. Positional changes in airway measurement by AR were present in the OSA group, with an average decrease in nasal cavity volume from upright to supine position of 1.53 cm(3) (p = 0.027). These changes were predictive of sleep apnea (r (2) = 0.65, p = 0.035). The authors concluded that these findigns showed a marked difference between OSA and PS groups during AR measurements of the nasopharynx. They stated that positional airway changes had been previously reported in adults with OSA and further evaluation of the airway function in pediatric OSA is warranted.
Andre and colleagues (2009) evaluated the correlation between the subjective sense of nasal patency and the outcomes found with rhinomanometry and AR. Review of English-language articles in which correlations were sought between subjective nasal patency symptoms and objective scores as found with rhinomanometry [nasal airway resistance (NAR)] and AR [minimal cross-sectional area (MCA)]. Correlations were related to unilateral or combined assessment of nasal passages and to symptomatic nasal obstruction or unobstructed nasal breathing. A total of 16 studies with a level of evidence II-a or II-b fit the inclusion criteria and were further analyzed. Almost every possible combination of correlations or lack thereof in relation to the variables included was found. However, when obstructive symptoms were present, a correlation between the patency symptoms with nasal airway resistance and minimal cross-sectional area was found more often than in the absence of symptoms. In cases of bilateral assessment a correlation was found almost as often as it was not between patency symptoms and total nasal airway resistance or combined minimal cross-sectional areas, while in the limited amount of studies in which unilateral assessment was done a correlation was found each time between patency symptoms and nasal airway resistance. The authors concluded that the correlation between the outcomes found with rhinomanometry and AR and an individual's subjective sensation of nasal patency remains uncertain. Based on this review, it seems that the chance of a correlation is greater when each nasal passage is assessed individually and when obstructive symptoms are present. There still seems to be only a limited argument for the use of rhinomanometry or AR in routine rhinologic practice or for quantifying surgical results.
Kupczyk et al (2010) evaluated AR as an objective method of assessment of nasal lysine aspirin (Lys-ASA) nasal challenge. A total of 20 patients with aspirin induced asthma (ASA-S) and 10 controls (ASA-NS): 5 patients with allergic rhinitis and 5 healthy subjects) were included. Nasal challenge was performed with placebo (saline) and 14.4 mg of Lys-ASA introduced as aerosol to both nostrils (total dose: 16 mg of acetylsalicylic acid). Measurements of nasal volume bilaterally were performed with the use of AR before and 1, 2, 4 and 24 hours after the challenge. For further analysis the sum of both nasal cavities volume at the level of 2 to 5 cm from nostrils was used. Mean total bilateral volume in ASA-S group after placebo was: 7.74, 6.21, 7.11, 7.12, 7.24 cm(3) and 7.24, 5.77, 6.31, 6.27, 6.98 cm(3) after Lys-ASA (before and after 1, 2, 4 and 24 hours, respectively; p = 0,048 and p = 0,02, in 2nd and 4th hour, Lys-ASA versus placebo, Wilcoxon's test). With cut-off point of nasal volume decrease by 10 % in the 1st hour the sensitivity of the test was 70 %, specificity 60 %, positive predictive value 77.78 % and negative predictive value 50 %. The authors concluded that AR with measurement of nasal cavities volume changes at 2 to 5 cm from nostrils does not appear to be sufficiently sensitive and specific as a single method for evaluation of studied challenge method.
Optical rhinometry (ORM) is a new technique introduced in Germany in 2004 that quantifies light extinction in optical density to assess nasal blood volume as a measure of nasal patency. It works via optical spectroscopy, which measures the absorption of visible and near-infrared light in tissue. Similar to pulse oximetry that measures hemogblobin absorption of near-infrared light and thus oxygen blood saturation, ORM measures blood volume within the nasal cavity. An emitter and detector are positioned across the nasal bridge, and swelling is measured as the extinction of light or optical density, as a function of time.
Hellgren and colleagues (2007) validated the Rhinolux (Rhios GmbH, Germany), an optical rhinometer, against AR in detecting nasal mucosal swelling when changing body position from sitting to supine. The study population consisted of 20 healthy subjects (7 women, 13 men, mean age of 34.7 +/- 9.3 years). The Rhinolux was applied sitting in the upright position followed by 5 mins in the supine position. Acoustic rhinometry was measured sitting in the upright position and after 5 mins in the supine position. In 7 subjects the measurements were repeated on 3 different days to assess the repeatability. The mean change from baseline in minimal cross sectional area DeltaMCA measured with acoustic rhinometry was -0.12 (+/- 0.19) cm2 (right + left side), p = 0.013 but DeltaE (change in light extinction from baseline) measured with the Rhinolux was unchanged 0.02 (+/- 0.18) optical densities (OD), p = 0.56. There was no correlation between DeltaE and DeltaMCA r = 0.028, p = 0.9. The mean DeltaE result from repeated measurements on different days was 0.05 (+/- 0.08) OD, p = 0.09 and the DeltaMCA was -0.1 (+/- 0.11) cm2, p = 0.02. This study showed that the changes in nasal blood volume measured with the Rhinolux did not reflect changes in nasal mucosal swelling measured with AR when changing body position from sitting to supine. The results indicated that the utility of the Rhinolux in assessing nasal mucosal reactions has to be evaluated further.
In a prospective pilot study, Luong et al (2010) evaluated ORM as an objective evaluation of nasal patency using nasal provocation testing (NPT) with histamine and oxymetazoline. A total of 5 adult subjects with allergic rhinitis and 5 adult normal subjects who underwent challenge with histamine and oxymetazoline were included in this study. Patients underwent challenge with increasing concentrations of histamine to determine the amount of histamine needed to cause a positive ORM reading. The same subjects then underwent histamine challenge with this amount followed by oxymetazoline. Nasal patency was assessed subjectively after each challenge with the visual analog scale. The median histamine amount needed to cause a positive response was statistically lower in allergic rhinitis as compared with non-allergic subjects at 150 microg and 300 microg, respectively (p = 0.04). When comparing ORM with subjective nasal congestion after histamine and oxymetazoline challenges, there was a statistically significant correlation with r = 0.79 (p = 0.00003). The authors concluded that the findings of this pilot study demonstrated a correlation between subjective symptoms of nasal patency and objective measurements with ORM. Less histamine amount necessary to incite nasal congestion in allergic rhinitis suggests that these patients may be primed to the effects of histamine. They stated that these preliminary findings serve to create the foundation for further exploration of the utility of ORM for NPT.
In a prospective pilot study, Cheung et al (2010) assessed ORM as an objective evaluation of nasal patency using NPT with Dermatophagoides farinae (Df) as compared with AR. A total of 5 adult healthy controls and 5 adult subjects with allergic rhinitis underwent NPT with increasing concentrations of Df while undergoing ORM. The minimum concentration of Df causing a positive reading was recorded. Nasal cross-sectional area was measured before and after testing using AR. Nasal patency was assessed subjectively after each challenge with the visual analog scale. The median amount of Df causing a positive response on ORM was less in allergic rhinitis patients as compared to healthy controls, at 5000 AU/ml and greater than 10,000 AU/ml, respectively. There was a statistically significant correlation between the change in optical density in ORM and subjective nasal congestion after increasing Df challenges (r = 0.63; p = 0.0007). Similarly, there was a statistically significant correlation between change in optical density by ORM and both minimum cross-sectional areas as measured by AR (r = -0.60, p = 0.03; and r = -0.64, p = 0.02, respectively). The authors concluded that this is the first study to show a correlation between ORM and AR during NPT with Df. In addition, the data support a correlation of ORM to subjective symptoms of nasal congestion. These findings suggest that ORM is able to assess changes in nasal patency during challenges with Df. They stated that further studies on ORM are needed; current ongoing trials are evaluating ORM for NPT with other common antigens.
Tombu et al (2010) stated that AR and RMM study 2 different parameters of nasal ventilation: (i) respiratory function and (ii) the anatomy of nasal cavities. These researchers examined the usefulness of AR and RMM, in particular in the surgical field. They listed the normal values for these tests. Nasal obstruction is a symptom of multi-factorial origin. Nasal patency is only one factor influencing the sensation of nasal ventilation. Despite the range of divergent opinions in both the literature and among rhinological clinicians, the objective assessment of nasal patency in functional rhinoplasty or septo-rhinoplasty seems to be advisable. The authors stated that the roles of AR and RMM still have to be established.
de Aguiar Vidigal et al (2012) evaluated the nose of patients with OSA syndrome (OSAS), compared them to controls, and correlated the different methods used to evaluate the nose. A total of 47 patients with moderate-to-severe OSAS and 20 controls who were matched for gender, age, and BMI were included. Questionnaires regarding sleep and nasal symptoms, physical examination, AR, naso-fibroscopy, rhinoscopy, as well as nasal inspiratory peak flow (NIPF) measurements were performed. In the OSAS group, 33 (70.2 %) were male, with a mean age of 53.2 +/- 9.1 years. In the control group, 13 (65 %) were male, with a mean age of 53.7 +/- 9.7 years. The OSAS group had a higher score on the nasal symptoms scale (p < 0.01) and a higher frequency of nasal alterations [presence of septal deviation, clinical complaints (p = 0.01) and hypertrophy of the inferior nasal turbinate (p < 0.01)]. The NIPF and AR parameters could not differentiate between the OSAS and control groups. There were no significant correlations among the different methods used to evaluate the nose. Lower NIPF values were capable of predicting higher apnea-hypopnea index scores (p = 0.007). The authors concluded that clinical complaints and nasal alterations as measured by rhinoscopy and naso-fibroscopy were associated with the presence of OSAS, which was not the case for theAR and NIPF parameters. The results of different evaluation methods were not correlated with each other.
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