Exhaled Nitric Oxide in Chronic Obstructive Pulmonary Disease

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Abstract
Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow obstruction and a neutrophilic inflammation. Exhaled nitric oxide (NO) may be a marker of disease activity in a variety of lung diseases. We measured exhaled NO in patients with documented COPD and investigated whether the concentration of exhaled NO is related to the severity of disease as defined by lung function. We also investigated whether concentration of exhaled NO was different in COPD patients who received inhaled steroids compared with steroid-naı̈ve patients. We studied 13 current smokers with COPD, eight exsmokers with COPD, 12 patients with unstable COPD (exacerbation or severe disease), and 10 smokers with chronic bronchitis without airflow limitation. Exhaled NO levels were significantly higher in patients with unstable COPD (12.7 ± 1.5 ppb) than in other groups (p < 0.01). Exhaled NO levels were significantly higher in smokers with COPD than in smokers with chronic bronchitis (4.3 ± 0.5 versus 2.5 ± 0.5 ppb, p < 0.05), and were even higher in patients with COPD who had stopped smoking (6.3 ± 0.6 ppb, p < 0.01). Exhaled NO levels showed a significant negative correlation with their lung function assessed by % predicted FEV1 values (r = − 0.6, p < 0.001). Exhaled NO levels in patients treated with inhaled steroids were significantly higher compared with steroid-naı̈ve patients (8.2 ± 1.2 ppb versus 5 ± 0.4 ppb, p < 0.05), but the first group included more severe patients as assessed by lung function. We conclude that exhaled NO could serve as a useful, practical marker for monitoring disease activity in COPD.