Chest
Volume 120, Issue 2, August 2001, Pages 496-501
Journal home page for Chest

Clinical Investigations
Techniques
Exhaled Carbon Monoxide and Nitric Oxide in COPD

https://doi.org/10.1378/chest.120.2.496Get rights and content

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 FEV1 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.

Section snippets

Study Subjects

The following four groups of subjects were studied: 10 healthy nonsmokers; 12 healthy smokers; 15 patients with COPD who were ex-smokers; and 15 patients with COPD who were current smokers (Table 1). Patients with COPD attended the outpatient clinic at the Royal Brompton Hospital in London. Informed consent was obtained from all subjects. This study was approved by the Ethics Committee of the Royal Brompton Hospital and Harefield Trust. Study groups were matched for age (Table 1). The diagnosis

Results

The clinical data for healthy subjects and patients with COPD are summarized in Table 1.

Discussion

Oxidative stress is a major component of airway inflammation in patients with COPD.1 In this study, we have suggested a potential new noninvasive method to monitor airway inflammation and oxidative stress in stable ex-smokers with COPD that is based on exhaled NO and CO measurements. Since the levels of exhaled CO and NO are strongly affected by cigarette smoking, their usefulness in current smokers is limited. We found a 2.5-fold increase in the level of exhaled CO in ex-smokers with COPD

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    Dr. Montuschi was the recipient of Research Fellowship from the National Research Council of Italy.

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