Exhaled nitric oxide in stable chronic obstructive pulmonary disease

STUDY OBJECTIVE: The objective of the study was to test the hypothesis that fraction of exhaled nitric oxide (FENO) is elevated in nonsmoking subjects with stable chronic obstructive pulmonary disease (COPD) and compare it with the results in patients with asthma and a control population.

DESIGN: Cross-sectional study.

MATERIALS AND METHODS: Pulmonology Clinic at a University Hospital. Twenty five control subjects, 25 steroid naïve asthmatics and 14 COPD patients were studied. All the patients were nonsmokers and stable at the time of the study. All subjects completed a questionnaire and underwent spirometry. Exhaled nitric oxide was measured online by chemiluminescence, using single-breath technique.

RESULTS: All the study subjects were males. Subjects with stable COPD had significantly higher values of FENO than controls (56.54+/-28.01 vs 22.00+/-6.69; P=0.0001) but lower than the subjects with asthma (56.54+/-28.01 vs 84.78+/-39.32 P=0.0285).The FENO values in COPD subjects were inversely related to the FEV/₁FVC ratio. There was a significant overlap between the FENO values in COPD and the control subjects.

CONCLUSION: There is a significant elevation in FENO in patients with stable COPD, but the elevation is less than in asthmatic subjects. Its value in clinical practice may be limited by the significant overlap with control subjects.