[Acoustic rhinometry: the bat principle of the nose]

All cross-sectional areas of the upper airway can be measured by an acoustic signal using the acoustic reflection technique, or acoustic rhinometry. The plane of the cross-sectional areas measured was determined in nasal models. The isotemporal layers were found to be nearly parallel to the nasal valve. The acoustically measured cross-sectional areas correlated with the cross-sectional areas of cuts from nasal models. After digitizing these cuts, a CAD software calculates cross-sectional areas in all orientations and at all distances. The difference between the measured and calculated cross-sectional areas is up to 3% in the nasal cavity and up to 17% in the nasopharynx. The hypothesis that the cross-sectional areas measured lie nearly parallel to the nasal valve was confirmed. The normal rhinometric curve shows the minimal cross-sectional area (I-notch) to lie at the nasal isthmus. The second narrowest segment of the nasal cavity lies at the head of the inferior concha and septal concha (C-notch). Characteristic examples of patients with turbinate hypertrophy, choanal atresia, enlarged adenoids, and septal deviations are presented. Acoustic rhinometric curves can only be interpreted in combination with the rhinoscopic findings because different pathological conditions can produce similar curves. Recording of reliable and reproducible data by acoustic rhinometry demands that the connection between the rhinometer and the nose does not distort the valve area. When we used two different nose pieces (1.2 and 1.5 cm outer diameter) the cross-sectional areas in the anterior third of the nose of only 28% of the patients was measured correctly.(ABSTRACT TRUNCATED AT 250 WORDS)