Objective:
The aim of this study was to estimate the reference values for nasal inspiratory flow in the study population in Poland as part of the project on Epidemiology of Allergic Diseases in Poland (ECAP).

Material and Methods:
The study subjects were a group of 4,137 people: 1,136 children aged 6–7 years (561 girls and 575 boys), 1,123 adolescents aged 13–14 years (546 girls, 577 boys) and 1,878 adults (1,145 women, 733 men), residing in seven large Polish cities. The method used in the study was the measurement of the peak nasal inspiratory flow (PNIF) using a special mask for rhinomanometry tests, with a measurement scale of 20–350 L/min. Measurements were conducted twice: once before and once after nasal mucosa vasoconstriction with a 0.1% xylometazoline (Xylometazolinum) solution.

Results:
Nasal patency rates increased with age in healthy subjects (children aged 6–7 years: 75.95 L/min; teenagers aged 13–14 years: 91.44 L/min and adults: 97.13 L/min (P<0.05). Similarly significant correlations were observed in the study group based on the region of residence (P<0.05). A moderate correlation was observed between PNIF and height as well as weight (with correlation coefficients r=0.51, P<0.05; and r=0.49, P<0.05, respectively). Interestingly, the observed difference in nasal vasoconstriction varied considerably between study subgroups with respect to the pre-determined criteria of age, gender, place of residence, and clinical diagnosis (allergic rhinitis vs. healthy controls), with the mean rates of 25–28%.

Conclusions:
Any attempt to determine reference values for a given study population should include a number of variables, such as age, height, body weight, which can noticeably affect study results.