Acoustic rhinometry in the evaluation of nasal obstruction

Abstract

Acoustic rhinometry (AR) is a recently developed objective technique for assessment of geometry of the nasal cavity. The technique is based on the analysis of sound waves reflected from the nasal cavities. It measures cross-sectional areas and nasal volume (NV). To obtain dependable assessments of nasal resistance by rhinomanometry or cross-sectional area measurements by AR, it is essential that the structural relations of the compliant vestibular region remain undisturbed by the measuring apparatus. The use of nozzles in making these measurements carries a great risk of direct distortion of the nasal valve. We used a nasal adapter that does not invade the nasal cavity and a chin support that stabilizes the head. In 51 healthy nasal cavities, the average minimum cross-sectional area (MCA) was 0.62 cm2 at 2.35 cm from the nostril and 0.67 cm2 at 2 cm from the nostril, respectively, before and after topical decongestion of the nasal mucosa. The MCA and NV findings in this group were significantly higher than MCA and NV (P < 0.001) in people with structural or mucosal abnormalities before mucosal decongestion. After mucosal decongestion, the MCA and NV were significantly higher in healthy nasal cavities than in nasal cavities with structural abnormalities (P < 0.001) but were not higher than nasal cavities with mucosal abnormalities (MCA, P = 0.05; NV, P = 0.06). A nozzle was applied in 20 healthy nasal cavities after mucosal decongestion, and a significantly higher MCA was found compared to measurements made with the nasal adapter (P = 0.02). We conclude that the nasal adapter, which does not invade the nasal cavities, avoids the distortion of the nasal valve and gives more accurate results.

Áreas seccionais nasais de adultos sadios aferidas por rinometria acústica

“…It is important to mention that in this case specifically the subject's contralateral cavity had an area of 0.78cm 2 , thus compensating for the likely structural or functional unilateral obstruction and sensation of adequate nasal patency. Secondly, the tests were carefully performed to take into account and control the variables pointed by other authors 7,14,29 that could impact measurement accuracy and reproducibility, such as ambient temperature, external noise, rhinometry tube position, sound losses, head position, nostril deformation, equipment calibration, and interferences from breathing and swallowing. By doing so in other studies carried out at our laboratory, we observed variation in cross-sectional area rhinometry measurements ranging between 6% and 9% 30 .…”

“…The papers cited above are quite recent, and two used the same equipment employed in our study. In all others [14][15][16][17][20][21][22] , the average CSA1 values ranged between 0.60cm 2 and 0.78cm 2 . This difference may be attributed to the fact that most studies -specially the ones done longer ago -used olive-type nasal adapters which ae known to introduce nasal cavity deformation, thus leading to overestimated cross-sectional area measurements 14,29 .…”

“…In all others [14][15][16][17][20][21][22] , the average CSA1 values ranged between 0.60cm 2 and 0.78cm 2 . This difference may be attributed to the fact that most studies -specially the ones done longer ago -used olive-type nasal adapters which ae known to introduce nasal cavity deformation, thus leading to overestimated cross-sectional area measurements 14,29 . Other factors that may explain the observed differences are the characteristics and the size of the analyzed sample, the type of equipment employed, and even the differences related to factors that may potentially introduce error in the measurements as mentioned before 7,27 .…”

“…Normal cross-sectional area values have been reported by many authors [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] , whose findings are summarized on Chart 1. Nonetheless, due to factors such as ethnic, weather, and laboratory-related differences, local reference values must be determined, as stressed by Hilberg and Pedersen 7 and Roithman 26 more recently.…”

Efeitos da alteração de postura sobre a permeabilidade nasal

“…It may have resulted from the fact that the acoustic rhinometry was performed only 5 minutes after taking the seated position again. Another explanation may be lack of correlation demonstrated in other studies between findings of objective exams, such as nasal rhinoscopy and acoustic rhinometry, and perception of breathing 15 . Moreover, Kase et al 3 showed that the minimum area seems to be more sensible than volume to detect posture changes.…”