Computer-aided rhinometry. A research rhinometer for clinical trial.

The effects of several variables on work of nasal breathing and nasal resistance were investigated. Sampling of pressure and flow of nasal respiratory air was performed by posterior rhinometry every 20 msec with a microprocessor and standard respiratory laboratory equipment. This technique enables work of nasal breathing and mean nasal resistance to be determined on line. The relationship between work-litre-1 and ventilation was always near-linear and its slope is the dimensional equivalent of resistance. Slope and linearity remained constant for several hours at a time and were unaffected by moderate hyperventilation, exercise, or change in breathing pattern. The slope of the line--but not its linearity--was altered by vasoactive medication exercise and nasal obstruction. Mean nasal resistance determined by this technique may be employed as a measure of nasal obstruction, its stability and independence from the moderate changes in breathing pattern which occur spontaneously suggest a useful clinical application.