Exhaled carbon monoxide and nitric oxide in COPD

Study objectives; To investigate whether exhaled carbon monoxide (CO) and n itric oxide (NO) could be used as noninvasive in vivo biomarkers of oxidati ve stress in the lungs of patients with COPD. Design: Single-center cross-sectional study. Patients: Ten healthy nonsmokers, 12 smokers, 15 stable ex-smokers with COP D, and 15 stable current smokers with COPD. Interventions: Subjects attended the outpatient clinic on one occasion for pulmonary Function tests and exhaled CO and NO measurements. Measurements and results: Mean (+/- SEM) CO levels in ex-smokers with COPD were higher (7.4 +/- 1.9 ppm; p < 0.05) than in nonsmoking control subjects (3.0 +/- 0.3 ppm) but were lower than in current smokers with COPD (20.0 /- 2.6 ppm; p < 0.001). There was no correlation between exhaled CO and NO. There was no correlation between CO and lung function tests in any group o f patients. Exhaled NO was higher in ex-smokers with COPD (12.0 +/- 1.0 par ts per billion [ppb]; p < 0.001) than in healthy nonsmokers (6.5 +/- 0.6 pp b) and in current smokers with COPD (7.6 +/- 1.1 ppb; p < 0.01) compared to healthy smokers (3.3 +/- 0.4 ppb). Ex-smokers with COPD had higher exhaled NO levels than did current smokers with COPD (p < 0.001) There was a negat ive correlation between exhaled NO and FEV1 in both ex-smokers with COPD (r = -0.60; p < 0.02) and cut-rent smokers, vith COPD (r = -0.59; p < 0.02). Conclusion: The measurement of exhaled CO and NO may represent a new method for the noninvasive monitoring of airway inflammation and oxidant stress i n COPD ex-smokers. Exhaled CO and NO are strongly affected by cigarette smo king, which limits their usefulness as biomarkers in current smokers.