Study objectives: To test the hypothesis that exhaled nitric oxide (NO) is increased in patients with chronic bronchitis, and to compare the results with exhaled NO in patients with asthma and COPD.
Study design: Cross-sectional survey.
Setting and patients: Veterans Administration pulmonary function laboratory. Patients (n = 179) were recruited from 234 consecutive patients. Two nonsmoking control groups of similar age, with normal spirometry measurements and no lung disease, were used (18 patient control subjects and 20 volunteers).
Measurements: Participants completed questionnaires and spirometry testing. Exhaled NO was measured by chemiluminescence using a single-breath exhalation technique.
Results: Current smoking status was associated with reduced levels of exhaled NO (smokers, 9. 2 +/- 0.9 parts per billion [ppb]; never and ex-smokers, 14.3 +/- 0. 6 ppb; p < 0.0001). Current smokers (n = 57) were excluded from further analysis. Among nonsmokers, the levels of exhaled NO were significantly higher in patients with chronic bronchitis (17.0 +/- 1. 1 ppb; p = 0.035) and asthma (16.4 +/- 1.3 ppb; p = 0.05) but not in those with COPD (14.7 +/- 1.0 ppb; p = 0.17) when compared with either control group (patient control subjects, 11.1 +/- 1.6 ppb; outside control subjects, 11.5 +/- 1.5 ppb). The highest mean exhaled NO concentration occurred in patients with both chronic bronchitis and asthma (20.2 +/- 1.6 ppb; p = 0.005 vs control subjects).
Conclusions: Exhaled NO is increased in patients with chronic bronchitis. The increase of exhaled NO in patients with chronic bronchitis was similar to that seen in patients with asthma. The highest mean exhaled NO occurred in patients with both chronic bronchitis and asthma. Exhaled NO was not increased in patients with COPD. Although chronic bronchitis and asthma have distinct histopathologic features, increased exhaled NO in patients with both diseases suggests common features of inflammation.