The counterintuitive decrease of exhaled nitric oxide (NO) levels in a severe inflammatory disorder like cystic fibrosis (CF) is only scarcely understood. Because NO is important in a variety of regulatory processes in the lung, including host defense, inflammation, and bronchomotor control, it is necessary to search for clarifying mechanisms.OBJECTIVES
To explore whether fractional exhaled NO (FENO) and nasal NO (nNO) levels are associated with CF genotype, nutritional status, presence of nasal polyps, pulmonary function, and airway colonization with Staphylococcus aureus and Pseudomonas aeruginosa in children with CF, and to investigate the effect of functional endoscopic sinus surgery (FESS) on FENO and nNO levels in children with CF and persistent sinonasal disease.DESIGN, SETTING, AND PARTICIPANTS
Cross-sectional study (association with NO) and prospective study (effect of FESS on NO) in a tertiary care referral center. Patients included 95 children with CF in clinically stable condition at routine annual multidisciplinary examination, 13 of whom were referred for a FESS procedure.INTERVENTIONS
Functional endoscopic sinus surgery in children with CF and persistent sinonasal disease.MAIN OUTCOMES AND MEASURES
Body mass index (BMI), FENO and nNO levels, results of flexible nasal endoscopy, pulmonary function tests (forced expiratory volume in 1 second and forced vital capacity), and airway cultures.RESULTS
Children with nasal polyposis have significantly lower nNO levels than those without polyposis (median, 53 vs 140 parts per billion; P = .001); these values are negatively associated with colonization with S aureus (β = −.22; P = .04). After FESS, nNO values increase significantly, although not to normal levels.CONCLUSIONS AND RELEVANCE
In children with CF, the presence of nasal polyps is associated with significantly lower nNO levels than in children without nasal polyps. After FESS for nasal polyposis, nNO levels increase significantly, but not to normal levels. Low nNO levels are associated with S aureus colonization in the oropharynx and lower airways.