PEAK NASAL INSPIRATORY FLOW - THE PLATEAU EFFECT

To study the efficacy of peak nasal inspiration flow (PNIF) as a means of recording change in nasal patency 20 subjects were given increasin g doses of intranasal xylometazoline. Nasal resistance (NR) and peak n asal inspiratory flow (PNIF) were measured in the resting state and af ter each xylometazoline administration. Successive increases in dose c aused a progressive decrease in nasal resistance and an increase in PN IF but the change in peak nasal inspiratory flow (PNIF) was much less. Peak nasal inspiratory flow shows a plateau effect as nasal resistanc e decreases. The reasons for this plateau are discussed in terms of re spiratory flow mechanics.