Acoustic rhinometry: accuracy and ability to detect changes in passage area at different locations in the nasal cavity

Internal nasal dimensions of children with unilateral cleft lip and palate and maxillary atresia: comparison between acoustic rhinometry technique and cone-beam computed tomography

PURPOSE

To compare the nasal cavity geometry of children and teenagers with cleft lip and palate and maxillary atresia by two methods: cone-beam computed tomography, considered the gold standard, and acoustic rhinometry.

METHODS

Data on cone-beam computed tomography and acoustic rhinometry examinations of 17 children and teenagers with cleft lip and palate and maxillary atresia, previously obtained for orthodontic planning purposes, were evaluated prospectively. Using Dolphin Imaging 11.8 software, the nasal cavity was reconstructed by two evaluators, and the internal nasal volumes were obtained. Using rhinometry, the volumes of regions V1 and V2 were measured. The values of each examination were then compared at a significance level of 5%.

RESULTS

Statistical analysis showed high intra- and inter-rater reproducibility in the cone-beam computed tomography analysis. The mean internal nasal volumes (± standard deviation) obtained using acoustic rhinometry and cone-beam computed tomography corresponded to 6.6 ± 1.9 cm3 and 8.1 ± 1.5 cm3, respectively. The difference between the examinations was 17.7%, which was considered statistically significant (p = 0.006).

CONCLUSION

The nasal volumes measured via the two methods were different; that is, they presented discrepancies in the measurements. The gold standard technique identified larger volumes than acoustic rhinometry in the nasal cavity. Therefore, determining which test reflects clinical reality is an essential future step.

Evaluation of Nasal Patency Among Patients With Unilateral Cleft Lip and Palate: Cleft Versus Non-Cleft Side

OBJECTIVE

To evaluate the nasal patency using acoustic rhinometry (AR) in patients with unilateral cleft lip and palate (UCLP) and to ascertain the rhinological importance of the same.

METHODS

Eccovision Acoustic Rhinometer system was used for assessment of nasal cross-sectional area (CSA) and volume in 15 patients with UCLP. The CSA1, CSA2, and CSA3, which represent the CSA at the nasal valve area and anterior end of the inferior turbinate, the anterior half of the inferior turbinate and the anterior end of the middle turbinate, and the region of middle portion of middle turbinate, respectively, were compared on the cleft and non-cleft side.

RESULTS

The mean ± SD of CSA1, CSA2, and CSA3 as well as the overall nasal CSA were significantly higher on non-cleft side compared to cleft side (P value < .001). The mean ± SD of nasal volume was also significantly higher in non-cleft side compared to cleft side (P value < .001).

CONCLUSIONS

The nasal patency among patients with UCLP demonstrates a range of impairments that can be objectively measured using acoustic rhinometry. The orthodontic, orthopedic, or orthosurgical management of maxillary deficiency in these patients can affect the nasal area and volume and can have an impact on breathing, speech, and sleep. The pretreatment assessment may be useful to identify patients who are at potential risk of deterioration of nasal patency and airway post-intervention. Taking into consideration the multiple diagnostic procedures in the course of long-term multidisciplinary treatment of patients with cleft lip and palate, a noninvasive investigation technique such as AR may be the preferred mode of investigation to ascertain nasal patency.

Investigating the nasal cycle using unilateral peak nasal inspiratory flow and acoustic rhinometry minimal cross-sectional area measurements

OBJECTIVE

To plot the nasal cycle using unilateral peak nasal inspiratory flow (UPNIF) and unilateral minimal cross-sectional area (UMCA) readings demonstrating a linear relationship in normal nasal function. Additionally, to determine how this changes in abnormal nasal function.

DESIGN

A cross-sectional study measuring UPNIF and UMCA in controls demonstrating normal nasal function and in patients with nasal obstruction.

SETTING

Royal National Throat Nose and Ear Hospital, London.

PARTICIPANTS

A total of 39 participants, 26 controls and 13 patients, were recruited. Controls exhibited normal nasal function with SNOT-22 <5. Patients nasal obstruction symptoms secondary to inflammation or structural abnormality with SNOT-22 >9.

MAIN OUTCOME MEASURES AND RESULTS

Airflow rates and resistance values were derived from UPNIF and UMCA measurements respectively based on Poiseuille's laws. Ratios between right and left UPNIF and UMCA values were taken to adjust for confounding factors. The relationship of 1/Resistance Ratio and Airflow Rate Ratio demonstrated a linear of direct proportionality of strong correlation and statistical significance (correlation coefficient = 0.76, P « 0.01). This suggests that data points from controls with a normal nasal cycle lie closely along the regressed line, whilst those lying significantly away were shown to belong to patients with nasal dysfunction. Olfactory dysfunction appears to be a sensitive discriminator in predicting this.

CONCLUSION

This study demonstrates the directly proportional relationship of 1/Resistance Ratio and Airflow Rate Ratio in normal nasal function. Furthermore, nasal pathology can be predicted if data points lie significantly outside these normal limits. Further studies are needed to validate exact normal and abnormal thresholds.

Velar activity in individuals with velopharyngeal insufficiency assessed by acoustic rhinometry

Acoustic rhinometry is routinely used for the evaluation of nasal patency.

OBJECTIVE

To investigate whether the technique is able to identify the impairment of velopharyngeal (VP) activity in individuals with clinical diagnosis of velopharyngeal insufficiency (VPI).

METHODS

Twenty subjects with repaired cleft palate and inadequate velopharyngeal function (IVF) and 18 non-cleft controls with adequate velopharyngeal function (AVF), adults, of both genders, were evaluated. Area-distance curves were obtained during VP rest and speech activity, using an Eccovision Acoustic Rhinometry system. Volume was determined by integrating the area under the curve at the segment corresponding to the nasopharynx. VP activity (ΔV) was estimated by the absolute and relative differences between nasopharyngeal volume at rest (Vr) and during an unreleased/k/ production (Vk). The efficiency of the technique to discriminate IVF and AVF was assessed by a ROC curve.

RESULTS

Mean Vk and Vr values (± SD) obtained were: 23.2 ± 3.6 cm3 and 15.9 ± 3.8 cm3 (AVF group), and 22.7 ± 7.9 cm3 and 20.7 ± 7.4 cm3 (IVF group), corresponding to a mean ΔV decay of 7.3 cm3 (31%) for the AVF group and a significantly smaller ΔV decay of 2.0 cm3 (9%) for the IVF group (p < 0.05). Seventy percent of the IVF individuals showed a ΔV suggesting impaired VP function (below the cutoff score of 3.0 cm3 which maximized both sensitivity and specificity of the test), confirming clinical diagnosis.

CONCLUSION

Acoustic rhinometry was able to identify, with a good discriminatory power, the impairment of VP activity which characterizes VPI.

The effect of nasal structure on olfactory function in patients with OSA

The aim of this study was to investigate the relationship between nasal structure and olfactory function in patients with obstructive sleep apnea (OSA). Olfaction and nasal structure of 76 adults with OSA diagnosed by polysomnography were measured using acoustic rhinometry and the Sniffin, Sticks (SS) smell test at Anzhen Hospital, a major academic center in Beijing, China. We tested the hypothesis that nasal structure in these patients would correlate with objectively measured olfactory performance. Minimum cross-sectional area (MCA) of the nose was significantly correlated with SS composite score (r = 0.434, p < 0.001), a result that was driven by two of the test's three components: olfactory threshold (OT) (r = 0.385, p = 0.001) and olfactory discrimination (OD) (r = 0.370, p = 0.001) but not olfactory identification (OI) (p > 0.05). Additionally, nasal volume (NV) was associated with composite SS score (r = 0.350, p = 0.002), a finding driven by OT (r = 0.283, p = 0.014). These data suggest that nasal structure affects parameters of olfactory function, likely via alterations in nasal airflow. Thus, anatomic abnormalities and diseases involving airflow (such as OSA) may cause, in part, olfactory dysfunction that is amenable to treatment. We speculate that surgery that alters nasal volume and MCA may improve olfactory performance.

Learning curve of septoplasty with radiofrequency volume reduction of the inferior turbinate

Objectives

Since few studies on surgical training and learning curves have been performed, majority of inexperienced surgeons are anxious about performing operations. We aimed to access the results and learning curve of septoplasty with radiofrequency volume reduction (RFVR) of the inferior turbinate.

Methods

We included 270 patients who underwent septoplasty with RFVR of the inferior turbinate by 6 inexperienced surgeons between January 2009 and July 2011. We analyzed success score, cases of revision, cases of complication, operation time, and acoustic rhinometry.

Results

Success score was relatively high and every surgeon had few cases of revision and complication. No significant difference was found in success score, revision, complication case, or acoustic rhinometry values between early cases and later cases. Operation time decreased according to increase in experience. However, there was no significant difference in the operation time after more than 30 cases.

Conclusion

We can conclude that 30 cases are needed to develop mature surgical skills for septoplasty with RFVR of the inferior turbinate and that training surgeons do not need to be anxious about performing this operation in the unskilled state.

Measurements of normal nasal airway assessed by 3-dimensional computed tomography in Chinese children and adolescents

OBJECTIVE

To establish normative data of nasal airway dimensions in Chinese children and adolescents by age and sex.

METHODS

CT images of 281 Chinese children and adolescents (140 girls and 141 boys) aged from 6 to 18 years (yr) were selected among the patients who visited in Shanghai Ninth People's Hospital from September 2009 to August 2010. Subjects were divided into four age groups as group 1 (6-9 yr), group 2 (10-12 yr), group 3 (13-15 yr), and group 4 (16-18 yr). Child was defined as 6-12 yr, and adolescent as 13-18 yr. Nasal parameters were as follow: nasal volume (NV), length of nasal airway (NL), minimal cross-section area (CSA 1) and its location (D 1), inferior turbinate head's location (D 2) and its airway cross-section area (CSA 2), and cross-sectional area of choanal (CSA 3).

RESULTS

There was no significant sex dimorphism in nasal parameters in children (group 1 and group 2). In adolescents, male's nasal dimension were larger than female's. CSA 1, D 1, CSA 2, CSA 3, NL and NV correlated with age in male and female respectively.

CONCLUSIONS

Volume, length and cross-section area of nasal airway were correlated with age in Chinese children and adolescents aged from 6 to 18 yr. In children, nasal conformations of male and female are similar. In adolescents, sex dimorphisms in nasal parameters were significant.

Intersession repeatability of acoustic rhinometry measurements in healthy volunteers

Objectives

Acoustic rhinometry is a rapid, reliable and non-invasive technique for the evaluation of conditions associated with impaired nasal patency. This study aimed to examine the intersession repeatability of acoustic rhinometry measurements of unilateral and combined nasal parameters in a group of healthy volunteers.

Methods

Twenty healthy volunteers were studied. In each subject, acoustic rhinometry measurements were performed on five consecutive days, with multiple recordings. Five clinically relevant parameters were measured in each session and the intersession repeatability of these measurements was expressed in terms of mean coefficient of variation, intraclass correlation coefficient and inter-item correlations.

Results

Intraclass correlation coefficients showed a high, and greater repeatability over time for all the combined (mean) values compared to the unilateral values. All intraclass correlations for combined values were ≥0.80 confirming almost perfect agreement. All intraclass correlations and inter-item correlations were associated with P<0.001. The mean coefficient of variation was low (<10%) for all but the proximal minimum cross sectional area (MCA1) measurements.

Conclusion

Acoustic rhinometry provides highly repeatable measurements of nasal patency, which is best for combined (mean) nasal parameters. This property makes it suitable for use in the diagnosis and follow-up of conditions associated with nasal obstruction, either structural or functional.

Improvement of nasal airway ventilation after rapid maxillary expansion evaluated with computational fluid dynamics

INTRODUCTION

Rapid maxillary expansion is known to improve nasal airway ventilation. However, it is difficult to precisely evaluate this improvement with conventional methods. The purpose of this longitudinal study was to use computational fluid dynamics to estimate the effect of rapid maxillary expansion.

METHODS

Twenty-three subjects (9 boys, 14 girls; mean ages, 9.74 ± 1.29 years before rapid maxillary expansion and 10.87 ± 1.18 years after rapid maxillary expansion) who required rapid maxillary expansion as part of their orthodontic treatment had cone-beam computed tomography images taken before and after rapid maxillary expansion. The computed tomography data were used to reconstruct the 3-dimensional shape of the nasal cavity. Two measures of nasal airflow function (pressure and velocity) were simulated by using computational fluid dynamics.

RESULTS

The pressure after rapid maxillary expansion (80.55 Pa) was significantly lower than before rapid maxillary expansion (147.70 Pa), and the velocity after rapid maxillary expansion (9.63 m/sec) was slower than before rapid maxillary expansion (13.46 m/sec).

CONCLUSIONS

Improvement of nasal airway ventilation by rapid maxillary expansion was detected by computational fluid dynamics.

REM-associated nasal obstruction: a study with acoustic rhinometry during sleep

OBJECTIVE

Obstructive sleep apnea events are more common in REM sleep, although there is no relationship between sleep phase and pharyngeal airway status. We studied the patency of the nasal airway during REM and non-REM sleep with the use of acoustic rhinometry.

METHODS

Serial acoustic rhinometric assessment of nasal cross-sectional area was performed in 10 subjects, before sleep and during REM and non-REM sleep. All measurements were standardized to a decongested baseline with mean congestion factor (MCF).

RESULTS

MCF in the seated position was 10.6% (+/-3.7) and increased with supine positioning to 16.2% (+/-2.3). In REM sleep, MCF was highest, at 22.3% (+/-1.7). In non-REM sleep, MCF was lowest, at 2.3% (+/-3.1). All interstage comparisons were statistically significant on repeated measures ANOVA (P < 0.05).

CONCLUSION

REM sleep is characterized by significant nasal congestion; non-REM sleep, by profound decongestion. This phenomenon may be attributable to REM-dependent variation in cerebral blood flow that affects nasal congestion via the internal carotid system. REM-induced nasal congestion, an indirect effect of augmented cerebral perfusion, may contribute to the higher frequency of obstructive events in REM sleep.

Nasal Airway Volume and Resistance to Airflow

Background

In modern rhinological practice and research, rhinomanometry and acoustic rhinometry are widely used. The goal of this study was to determine whether there is correlation between rhinomanometrically derived nasal airflow resistances and acoustic rhinometrically derived nasal airway volumes.

Methods

To achieve the goal, a prospective cross-sectional study of a total of 316 patients complaining of nasal obstruction was performed. Resulting data were compared by means of Spearman rank correlations of the total number of patients and of subgroups.

Results

The total number of patients, and most subgroups, in both their untreated and decongested states showed significant negative correlation unilaterally between nasal airflow resistances and nasal volumes.

Conclusion

Rhinomanometric nasal airflow resistances and concurrent acoustic rhinometric nasal airway volumes are closely correlated. The combination of the two objective methods provides insight into nasal airflow physiology and nasal airway anatomy.

Choanal atresia: long-term follow-up with objective evaluation of nasal airway and olfaction

OBJECTIVE

The purpose of this study was to determine the status of nasal airway and olfaction of adult subjects born with choanal atresia (CA).

STUDY DESIGN AND SETTING

A case-control study was conducted to compare the quality of nasal airway and olfaction in a group of adults born with CA to a similar group of normal subjects. Objective evaluation of nasal airway and olfaction were done respectively by acoustic rhinometry and the University of Pennsylvania Smell Identification Test (UPSIT).

RESULTS

Thirty-six choanal atresia patients aged 16 to 36 were found in the medical records. Five bilateral and two unilateral cases were recruited for the study. An average score of 27/40 (moderate hyposmia) was obtained by the bilateral cases compared with 37/40 (normal) by the controls. These results were statistically significant (Wilcoxon signed rank test and sign test statistic, P = 0.03).

CONCLUSIONS

Using the UPSIT, the bilateral CA patients have shown, on average, a moderate loss of the sense of smell when compared with normal controls of a similar age group. Acoustic rhinometry is not a useful study for posterior nasal conditions.

[Diagnostic methods of nasal respiratory function]

Objective assessment of nasal obstruction may help with preoperative planning for rhinosurgery and indicate different aspects of endonasal pathology. To improve quality control, preoperative and postoperative objective assessment is desirable. This review presents objective functional diagnostic tools and explains their appropriate uses, the information obtained, and their limitations. An algorithm is presented for analysing nasal obstruction by means of objective functional assessment. Examples illustrate how to use this information for preoperative planning in rhinosurgery.

Acoustic rhinometry in healthy humans: accuracy of area estimates and ability to quantify certain anatomic structures in the nasal cavity

OBJECTIVES

We evaluated the accuracy of acoustic rhinometry (AR) measurements in healthy humans and assessed the ability of AR in quantifying the dimensions of the paranasal sinuses and certain anatomic structures in the nasal cavity.

METHODS

Twenty nasal passages of 10 healthy adults were examined by AR and computed tomography (CT) before and after decongestion. Actual cross-sectional areas of the nasal cavity and actual locations of the nasal valve, the head of the inferior turbinate, the head of the middle turbinate, the ostia of the frontal and maxillary sinuses, and the choana were determined from CT sections perpendicular to the curved acoustic axis of the nasal passage.

RESULTS

The AR-measured cross-sectional areas in the anterior nasal cavity were in reasonable agreement with the corresponding areas determined from CT, whereas AR consistently overestimated the passage areas at locations posterior to the paranasal sinus ostia. The nasal valve was identified as a pronounced minimum on the AR area-distance curve. However, AR did not discretely identify the head of the inferior turbinate, the head of the middle turbinate, or the choana.

CONCLUSIONS

The local minima on the AR area-distance curve beyond the nasal valve are caused by acoustic resonances in the nasal cavity, and do not correspond to any anatomic structure. The AR area overestimation beyond the paranasal sinus ostia is due to the interaction between the nasal cavity and the paranasal sinuses, rather than to sound loss into the sinuses. Acoustic rhinometry provides no quantitative information on ostium size or sinus volume in either non-decongested or decongested nasal cavities.

A Review of the Effects of Expansion of the Nasal Base on Nasal Airflow and Resistance

PURPOSE

The purpose of this article is to inform the reader of the current literature regarding nasal airflow resistance. The anatomy and physiology of nasal airflow resistance will be examined and the known effects of widening of the nasal airway upon airflow will be described.

MATERIALS AND METHODS

This article is a review of the current literature regarding nasal airflow and resistance and the effects of widening of the nasal base. No patient data were collected.

RESULTS

The literature shows that nasal airflow resistance can be changed by surgical manipulation and by rapid palatal expansion, but that the effects on airflow resistance and future growth and development are unpredictable.

CONCLUSION

Patients with a maxilla that is constricted in the transverse dimension and nasal airflow problems may benefit from expansion of the nasal base. The resultant effects upon nasal airflow resistance and subsequent growth and development are unpredictable and therefore airflow issues alone may not be a primary reason to increase the transverse dimension of the nasal base.