Reliability of acoustic rhinometry

In recent years increasing evidence has been provided on frequent simultaneous coexistence of inflammatory diseases and allergies in upper and lower airways. To achieve a good standard of measurement of upper airways, an objective method should be used. A total of 48 nasal cavities with nasal stuffiness associated with chronic sinusitis were measured with acoustic rhinometry (AR) and High-resolution computer tomography volumetry (HRCTV). Comparison of volumes and minimum cross-sectional areas measured with these methods was performed. The volumes measured from the nostril with both methods were the anterior (0-10 mm), middle (11-40 mm) and posterior (41-70 mm) volumes. The AR cross-sectional area curve was analysed based on two minimal notches corresponding to local minimal areas. A series of 1-mm coronal CT images without intervening gaps were made and analysed based on two minimal voxel values, which were later converted to cross-sectional areas corresponding to local, minimum cross-sectional areas (MCA). Furthermore, the distances of these 2 MCAs from the nostril were also measured. Strong statistically significant (P < 0.05) correlations were found between AR and computer tomography volumetry (CTV) volumes in the anterior (r = 0.83) and middle (r = 0.77) parts of the nasal cavity. In the posterior part of the nasal cavity a statistically significant (P < 0.05) correlation was also found (r = 0.62). Good agreements between the AR and CTV volumes in the anterior and middle parts of the nasal cavities were confirmed with Bland-Altman plots. Correlations among the MCAs were weaker (r = 0.59 and r = 0.55). Our results suggest that the reliability of AR appears sufficient for clinical and scientific use in the nasal cavities. Reliability is very good in the anterior and middle parts of the nasal cavities, while strong conclusions based on evaluation of the posterior part should be avoided due to decreasing accuracy.