Acoustic rhinometry: effects of decongestants and posture on nasal patency.

To determine whether acoustic rhinometry can be used to detect changes in nasal patency caused by decongestants or posture, we studied 10 healthy volunteers. Maps of the effective cross-sectional area of the nasal cavity as a function of distance into the respiratory system were generated, and an index of nasal cavity volume was calculated in the right and left nostril of each subject. The volume index was reproducible in subjects. The mean of the intrasubject coefficients of variation was 7.9%. After administration of phenylephrine in the form of a nasal spray, the volume index increased in the right nostril from 29.8 +/- 3.6 to 40.9 +/- 4.4 cm3 (mean +/- SEM) (p less than 0.001) and in the left nostril from 26.3 +/- 2.1 to 38.0 +/- 3.0 cm3 (p less than 0.001). On another occasion in the same subjects, the volume index was determined before and 90 minutes after oral administration of 60 mg pseudoephedrine. The volume index for the sum of both nostrils increased from 56.7 +/- 4.7 to 65.1 +/- 5.2 cm3 (p less than 0.5). In another group of subjects, turning from the supine position to the right side caused right nasal volume to decrease from 29.3 +/- 4.4 to 19.5 +/- 3.6 cm3 (p less than 0.003) and the left nasal volume to increase from 20.9 +/- 2.8 to 25.5 +/- 3.2 cm3 (p less than 0.05). We conclude that acoustic rhinometry can provide a sensitive index of changes in nasal geometry.