A Comparative Study of Fraction of Exhaled Nitric Oxide in Stable Chronic Obstructive Pulmonary Disease and Steroid Naive Asthma

Measurement of fraction of exhaled nitric oxide (FENO) is now being used in the diagnosis and management of bronchial asthma. Its value in chronic obstructive airway disease (COPD) is not well studied. This study was conducted to define the values of FENO in stable COPD patients in relation to steroid naive asthmatics and normal subjects. FENO was measured using the recent standard guidelines in 14 COPD patients, 25 asthmatic patients and 25 normal subjects. 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 subjects with asthma (56.54 +/- 28.01 vs 84.78 +/- 39.32 p< 0.0285). The FENO values in COPI) subjects were inversely related to FEV1/FVC ratio. There was a significant overlap between the FENO values in COPD and control subjects. We conclude that FENO is elevated 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.