Reference Equations for Peak Nasal Inspiratory and Expiratory Flow: A Cross-Sectional Study.

OBJECTIVE: To develop reference equations for peak nasal inspiratory flow (PNIF) and peak nasal expiratory flow (PNEF) in healthy adults using easily measurable anthropometric variables. METHODS: This cross-sectional study included 239 clinically healthy adults (123 women and 116 men) aged 20-55 years with normal spirometry and no clinically relevant nasal obstruction symptoms. PNIF and PNEF were measured using standardized techniques. Generalized linear models were constructed using sex, height, weight, and age as candidate predictors. Model selection was based on the corrected Akaike information criterion (AICc). RESULTS: Model m14 demonstrated the best fit and parsimony for both PNIF and PNEF. The final reference equation for PNIF was PNIF (L/min) = exp (3.370356 + 0.633324 × height (m) + 0.004086 × weight (kg) + 0.130967 × sex). The reference equation for PNEF was PNEF (L/min) = exp (2.799532 + 1.062786 × height (m) + 0.005143 × weight (kg) + 0.133738 × sex). Sex was coded as 0 for female and 1 for male. Height and weight showed significant positive associations with both outcomes. Age did not improve model performance. CONCLUSION: Reference equations for PNIF and PNEF were established in clinically healthy adults. Compared with PNEF, PNIF demonstrated greater homogeneity and lower residual variability, suggesting potential value as a complementary tool for interpreting objective nasal airflow measurements. These internally validated equations require external validation before broader clinical application. LEVEL OF EVIDENCE: N/A.