Nasal and Exhaled Nitric Oxide Is Reduced in Adult Patients With Cystic Fibrosis and Does Not Correlate With Cystic Fibrosis Genotype

Inducible nitric oxide synthase (iNOS) is upregulated in a number of inflammatory lung conditions, and exhaled nitric oxide (NO) concentration is increased. However, previous studies in children with cystic fibrosis (CF) have shown that exhaled NO is reduced. The purpose of this investigation was to study exhaled NO concentration in adults with CF, and to investigate the effect of CF genotype and respiratory tract infection on this measurement. Exhaled and nasal NO levels were measured in 54 adult CF subjects and 37 healthy nonsmoking age-matched subjects using a chemiluminesence analyzer. Spirometry (FEV1 and FVC), CF genotype, and bacterial colonization were also recorded. This study was conducted at a national CF center. The mean age of patients was 26.9 years, and the mean FEV1 was 50.5% predicted (range, 17 to 104%). Nasal NO in the CF patients (mean, 520 parts per billion[ppb]; confidence interval [CI], 452 to 588) was significantly lower (p < 0.001) than in control subjects (987 ppb; CI, 959 to 1,015). Exhaled NO was significantly lower (p < 0.001) in CF patients (5.0 ppb; CI, 4.1 to 6.1) than in control subjects (7.3 ppb; CI, 6.8 to 7.8). FEV1 did not correlate with nasal or exhaled NO. No association was observed between genotype and NO values or colonization with Pseudomonas aeruginosa. Despite the airway inflammation that is characteristic of CF, both nasal and exhaled NO were reduced. There was no association with genotype or infection status. As NO has bacteriostatic effects and may augment mucociliary clearance, this observation may be of clinical importance.