Reference equations for peak nasal inspiratory flow in Portuguese adults

Background: Peak Nasal Inspiratory Flow (PNIF) is a fast, simple and low-cost method to assess nasal patency. We aimed to (1)describe PNIF values in healthy Portuguese adults, (2)to assess which variables influence PNIF and (3)to compute a PNIF reference equation for this population. Methods: From the population-based, nationwide, observational study ICAR - Control and Burden of Asthma and Rhinitis (clinical trials.gov NCT01771120), we included 104 nonsmoking adults (71% females) classified as healthy after medical evaluation, questionnaires and spirometry; and without previous nasal surgery, nasal polyps on anterior rhinoscopy or recent acute respiratory infectious disease. Five PNIF measurements were recorded for each subject and the highest was used in analysis. Univariate and multiple linear regression analyses were used to determine the reference equation. Results: The mean (SD) age of the sample was 47(17) years. Overall, PNIF mean (SD) was 134(40) l/min; it was higher in men (152(44) l/min) compared to women (126(36) l/min; p=0.002).We observed positive significant correlations between PNIF and height (r= 0.33; p=0.001), FVC (r= 0.44; p 1 (r= 0.47; p 2 = 0.21) for PNIF (l/min) was 109.2 + 14.7& FEV 1 – 0.27*Age – 12.2 Gender [0-male; 1-female]. When lung function is not available, an alternative reference equation (adjusted r 2 = 0.18) is 188.5-0.76*Age-26.4*Gender[0-male; 1-female]. Conclusion: The reference equation for PNIF in healthy subjects that included FEV 1 , age and gender had the highest explained percentage of PNIF variability.