Comparison of calculated nasal resistance from Röhrer's equation with measured resistance at delta P150Pa.

Values of nasal resistance at delta P150Pa have been recommended by the International Standardization Committee for clinical use. However, this point seems somewhat high for quiet nasal breathing. To determine the usefulness of calculated nasal resistance at delta P150Pa from Röhrer's equation when transnasal pressure fails to reach the point, the values at delta P150Pa calculated from the method have been compared with actually measured nasal resistances at delta P150Pa by active anterior rhinomanometry with a nasal nozzle. The mean value of measured unilateral nasal resistance in 75 patients is 0.513 +/- 0.511 Pa/cm3/s on expiration and 0.335 +/- 0.193Pa/cm3/s on inspiration. The mean value of calculated nasal resistance from Röhrer's equation is 0.511 +/- 0.515Pa/cm3/s on expiration and 0.337 +/- 0.207Pa/cm3/s on inspiration. Correlations between measured and calculated nasal resistances have been assessed and are almost identical in both expiration and inspiration. Calculated nasal resistance at delta P150Pa from Röhrer's equation seems to be suitable for evaluation when transnasal pressure fails to attain the point.