Exhaled carbon monoxide and nitric oxide in COPD

Chest. 2001 Aug;120(2):496-501. doi: 10.1378/chest.120.2.496.


Study objectives: To investigate whether exhaled carbon monoxide (CO) and nitric oxide (NO) could be used as noninvasive in vivo biomarkers of oxidative 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 COPD, 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 of patients. Exhaled NO was higher in ex-smokers with COPD (12.0 +/- 1.0 parts per billion [ppb]; p < 0.001) than in healthy nonsmokers (6.5 +/- 0.6 ppb) 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 negative correlation between exhaled NO and FEV(1) in both ex-smokers with COPD (r = -0.60; p < 0.02) and current smokers with 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 in COPD ex-smokers. Exhaled CO and NO are strongly affected by cigarette smoking, which limits their usefulness as biomarkers in current smokers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers / analysis
  • Breath Tests
  • Carbon Monoxide / analysis*
  • Female
  • Humans
  • Lung Diseases, Obstructive / physiopathology*
  • Male
  • Middle Aged
  • Nitric Oxide / analysis*
  • Oxidative Stress
  • Smoking / physiopathology


  • Biomarkers
  • Nitric Oxide
  • Carbon Monoxide