Aetna considers rhinomanometry and acoustic rhinometry testing experimental and investigational because of a lack of clinical studies demonstrating that these tests improve clinical outcomes.

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 two 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.