Study objectives: 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.
Design: 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.
Setting: This study was conducted at a national CF
Results: 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.
Conclusions: 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.