Endogenous nitric oxide in patients with stable COPD: correlates with severity of disease.

BACKGROUND: Increased levels of exhaled nitric oxide (eNO) have been reported in asthmatic subjects but little information is available on eNO in patients with advanced chronic obstructive pulmonary disease (COPD). A study was undertaken to evaluate the levels of eNO in patients with stable COPD of different degrees of severity. METHODS: Peak and plateau values of eNO (PNO and PLNO, respectively) were evaluated in 53 patients with COPD and analysed according to the level of forced expiratory volume in one second (FEV1) and the presence of cor pulmonale (CP) (group 1, FEV1 < 35\% predicted with CP, n = 15; group 2, FEV1 < 35\% predicted without CP, n = 15; group 3, FEV1 > 35\% predicted, n = 23). Seventeen normal subjects served as controls. RESULTS: All the patients with COPD had reduced levels of PLNO compared with the controls (mean (SD) 6.3 (3.0) and 9.4 (2.8) ppb, respectively). In groups 1 and 2 PLNO levels were significantly lower than in subjects in group 3 (5.5 (2.9), 5.7 (3.5), and 7.1 (2.7) ppb, respectively; p < 0.01 ANOVA). In all subjects \% predicted FEV1 correlated slightly with PLNO but not with PNO. CONCLUSION: Patients with severe stable COPD have reduced levels of eNO compared with normal subjects. eNO levels are slightly related to the severity of airflow obstruction.