Background: Airway inflammation is an important mechanism underlying deterioration in COPD and can be noninvasively assessed by exhaled nitric oxide (Feno) and induced sputum (IS). We wished to examine the shortterm reproducibility of Feno and IS in a cohort of subjects with COPD.

Methods: We recruited 11 subjects (9 men; age, 46 to 69 years) with COPD (American Thoracic Society criteria) and FEV1 45 to 70% predicted. Feno and spirometry were assessed at baseline, 2, 4, and 6 weeks, and IS for differential cell count, leukotriene B4 (LTB4) and interleukin (IL)-8 at baseline, 4, and 6 weeks. Results: There was a significant decline in FEV1 (p 0.029) and FEV1/FVC ratio (p 0.001) over the study period. This was accompanied by a significant increase (geometric mean with 95% confidence limits) from 15.2 (10.9 to 21.2) to 23.6 (17.1 to 32.4) parts per billion (p 0.037) and LTB4 from 1.79 (1.03 to 3.11) to 3.57 (1.95 to 6.53) pg/mL (p 0.018). There was no significant change in total or differential cell counts or IL-8 for the group as a whole; however, the change in both Feno and IL-8 correlated with the change in percent neutrophil count (r 0.648, p 0.028) and (r 0.60, p 0.05). Additionally, IL-8 and percent neutrophil count showed a borderline correlation (r 0.34, p 0.056). Finally, FEV1 showed a strong negative correlation with percent neutrophil count (r 0.55, p 0.001). The induction of sputum was well tolerated by all subjects, although FEV1 fell significantly from 1.83 0.44 to 1.46 0.44 L.

Conclusion: The worsening lung function over the study period, perhaps related to seasonal/climatic change, was accompanied by a significant increase in Feno and LTB4. Feno may be related to neutrophil inflammation, which is driven by the chemoattractant IL-8. Feno and IS promise to be useful markers of airway inflammation in COPD but IS causes a significant fall in FEV1 requiring careful monitoring and appropriate caution.