Peak nasal inspiratory flow as an adjunct measure of respiratory function in paediatric cystic fibrosis

Background Chronic rhinosinusitis (CRS) is common in cystic fibrosis (CF) and affects quality of life (QoL), especially in children. Objective tools like Peak Nasal Inspiratory Flow (PNIF) may aid in assessing nasal obstruction and monitoring treatment, but their role in CF is not well established. Methods This prospective cohort study included 49 children (mean age: 11.4 ± 3.3 years) with CF or CFTR-related disorder (CFTR-RD) from a regional referral center. All underwent nasal endoscopy scored via the Lund-Kennedy (LK) system, spirometry (FEV₁), PNIF measurement, and QoL assessment using the Sinus and Nasal Quality of Life Survey questionnaire (SN-5) and a Visual Analogue Scale (VAS). Correlations between PNIF, clinical parameters, and subjective scores were analyzed. Results The mean age of participants was 11.4 ± 3.3 years; 53 % were male. All patients had CRS (mean LK score: 5.6 ± 4.2). The mean PNIF was 79.1 ± 32.3 L/min (z-score ≈ 0.00), and mean FEV₁ was 98.6 % ± 18 of predicted. PNIF was significantly higher in males than females ( p = 0.003). A significant inverse correlation was found between PNIF and LK score ( r = –0.538, p < 0.001), and a positive correlation between PNIF and FEV₁ ( p = 0.001). No correlations were observed between PNIF and QoL scores (VAS, SN-5) or between LK score and QoL. Genotype did not significantly influence PNIF-age trajectories. In a subgroup of patients on CFTR modulators, PNIF did not differ significantly from the rest of the cohort. Conclusion PNIF is a feasible, well-tolerated, and non-invasive method for assessing nasal airflow in children with CF. It correlates significantly with both sinonasal inflammation and pulmonary function, supporting its potential role as a surrogate marker of global airway health. Given its simplicity and physiological relevance, PNIF may serve as a valuable adjunct in clinical and research settings to monitor upper and lower airway interactions in pediatric CF. Further longitudinal studies are warranted to validate its sensitivity to therapeutic interventions.