Increased exhaled nitric oxide in patients with stable chronic obstructive pulmonary disease

Background-Nitric oxide (NO) plays an important role as an inflammatory mediator in the airways. Since chronic obstructive pulmonary disease (COPD) is characterised by airway inflammation, a study was undertaken to determine NO levels in the exhaled air of patients with COPD. Methods-Two groups of patients with clinically stable COPD were studied, 10 current smokers and 10 ex-smokers. Two control groups of healthy subjects consisting of 10 current smokers and 20 nonsmokers were also studied. Exhaled NO levels were measured by the collection bag technique and NO chemiluminescence analyser. Results-Mean (SE) levels of exhaled NO in ex-smokers and current smokers with COPD (25.7 (3.0) ppb and 10.2 (1.4) ppb, respectively) were significantly higher than in non-smoker and current smoker control subjects (9.4 (0.8) ppb and 4.6 (0.4) ppb, respectively). In current smokers with COPD exhaled levels of NO were significantly lower than in ex-smokers. In this latter group of patients there was a significant negative correlation between smoking history (pack years) and levels of exhaled NO (r = -0.8, p = 0.002). A positive correlation was seen between forced expiratory volume in one second (FEV1,) and levels of exhaled NO (r = 0.65, p = 0.001) in patients with COPD. Conclusions-These data show that exhaled NO is increased in patients with stable COPD, both current and ex-smokers, compared with healthy control subjects.