Exhaled nitric oxide parameters and functional capacity in chronic obstructive pulmonary disease

The extended exhaled nitric oxide (eNO) parameters, including peripheral or alveolar eNO, are investigational biomarkers in COPD. In this study, the hypothesis was tested that elevated peripheral eNO correlates with decreased functional capacity and lower global health status. Twenty-seven subjects with the Global Initiative for Chronic Obstructive Lung Disease stage 3 and 4 COPD were enrolled. Functional capacity and health status were tested using the 6 min walk test and St George's Respiratory Questionnaire (SGRQ) respectively. eNO parameters were estimated using multiple exhalation flow rates and were corrected for axial diffusion. The extended NO measurements were FE(NO)0.05 14.2 ppb (range 5.1-23.2), C(ANO) 4.6 ppb (2.2-6.9), D(awNO) 8.8 ml s(-1) (4.8-12.9), C(awNO) 83.2 ppb (29.9-128.7) and J'(awNO) 405 pl s(-1) (111-731). The distance traveled in the 6 min walk test was correlated with peripheral nitric oxide (r = -0.59, p = 0.03). SGRQ symptom score was correlated with maximum airway NO flux (r = -0.73, p = 0.01). SGRQ total score was correlated with maximum airway NO flux (r = -0.56, p = 0.05). In this study of subjects with severe COPD, peripheral nitric oxide correlated with functional capacity while large airway NO parameters correlated with symptom scores.