Fig. 4From: Dysregulation of the endothelial nitric oxide pathway is associated with airway inflammation in COPDSputum nitrate and nitrite concentration in COPD. Sputum nitrate and nitrite concentrations were analysed between patients with stable and exacerbated COPD (a and c; unpaired t-test, *p < 0.05), and between the onset and the recovery of an acute severe exacerbation (b and d; paired t-test, &p = 0.06). S-COPD: stable COPD, E-COPD: exacerbation of COPD. Data were analysed after log transformation and are shown as geometric mean and geometric standard deviationBack to article page