[Evaluation of the effects of nasal decongestants with acoustic rhinometry]

Acoustic rhinometry is a new method of evaluating the geometrical distributions of the cross-section and volume of the nasal cavity. Its characteristics are that of a nontraumatic procedure requiring minimal time for measurements. Eight males (27-39 years old) without nasal lesions were investigated with acoustic rhinometry before and after unilateral administrations of decongestants. Conventional nasal decongestants such as naphazolin nitrate 0.1% (Privina) and tetrahydrozoline hydrochloride 0.1%, as well as prednisolone 0.02% (Cor-tyzine), were used in solutions diluted 10 or 100 times. As to the method of decongestant application, we adopted the head tilt method, in the successive order of backward, lateral (toward the non-application side) tilt and backward. Each position was maintained for 30 seconds. Minimal cross sectional area of the nasal cavity, and nasal volume were evaluated with acoustic rhinometry. After the application of nasal drops, the minimal cross sectional area increased within 10 minutes, followed by a plateau level for one hour. With the application of nasal decongestants, an I-notch, corresponding to the nasal valve, was unchanged, whereas the C-notch, corresponding to the anterior and of the inferior turbinate, often shifted upwards. Thus, the minimal cross sectional area changed from an I-notch to a C-notch location. The volume of the nasal cavity increased within 10 minutes, and maintained a plateau level for one hour which was similar to that of the minimal cross sectional area. Changes in the ratio of the minimal cross sectional area were greater for less diluted solutions. Changes in the ratio of the nasal cavity were similar to those of the minimal cross sectional area.