[Influence of the angle between the nasal cavity axis and nosepiece in acoustic rhinometry]

We evaluated the influence of the angle between the nasal cavity axis and the nosepiece (made with acrylics) in acoustic rhinometry (AR). This study was composed of three experiments. In the first experiment, the influence of angulation on nasal volume was evaluated using a silicone nasal model based on a cast of the nasal cavity of a cadaver. The angle between the nosepiece and the horizontal plane was changed by 10 degrees, 40 degrees or 70 degrees, vertically; the angle between the nosepiece and the sagittal plane was similarly changed horizontally. The nasal volume, obtained as the AR area-distance curve from 6.9-14.1cm, was measured under each condition. While the horizontal change in angle did not significantly influence the result obtained by AR, in the vertical change, the measured value rose as the angle was decreased from 70 degrees to 10 degrees. In the second experiment, an evaluation in healthy subjects (5 males, 4 females, mean age 28.6 years) revealed the same tendency in changing the horizontal angle, whereas vertically a change of 10 degrees produced a significant decrease over that seen with angles of 40 degrees and 70 degrees. This result contradicted that obtained in the model study mentioned above. In studying the effect of changing the vertical angle, the volume of the posterior 5 cm and that of the anterior 2 cm of the nasal cavity was evaluated in the same subjects. The volume of the posterior 5 cm did not differ significantly among angles, while that of the anterior 2 cm showed the same trend as observed with the whole nasal cavity.(ABSTRACT TRUNCATED AT 250 WORDS)