Acoustic rhinometry: do we need a standardized operating procedure?

The usefulness of a standardized operating procedure for acoustic rhinometry was assessed in a study on 51 healthy volunteers. Nasal measurements were made with acoustic rhinometry before and after application of a topical nasal decongestant. Our standard operating procedure used three consecutive readings of anterior nasal volume to obtain a valid estimate of mean nasal dimensions. The mean measurement was only accepted as valid if the three readings had a coefficient of variation (CV) of less than 20%. Twenty-two out of 192 (11.5%) nasal cavities required more than three consecutive readings to achieve this. Our data show that the error encountered by relying on a single reading of an acoustic trace can be greater than the changes caused by the topical nasal decongestant and that multiple readings using a standard operating procedure are essential to obtain valid data.