Alveolar nitric oxide (CA(NO)) has been suggested as a surrogate marker of distal airway inflammation in COPD. Coarse particle-inhaled corticosteroids (ICS) have been shown not to suppress CA(NO). We evaluated whether extra-fine particle size ICS (HFA-BDP) or systemic oral corticosteroids could suppress CA(NO) in COPD.
Chronic obstructive pulmonary disease (COPD) patients with a FEV1/FVC ratio < 0.7, FEV1 < 80% predicted with CA(NO) > 2 ppb underwent a double-blind randomized, controlled, crossover trial with an open-label systemic steroid comparator. After a 2 week steroid washout period, participants were randomized to 3 weeks of 100 mcg of HFA-BDP twice daily and then 3 weeks of 400 mcg of HFA-BDP twice daily, or matched placebos with subsequent crossover. All patients then received 1 week open-label, 25 mg/day of prednisolone. Exhaled nitric oxide, plasma cortisol, and lung function were recorded. CA(NO) was corrected for axial diffusion.
In 16 participants, there were no significant differences seen with either dose of HFA-BDP compared with placebo. Oral prednisolone significantly reduced FENO and J'aw(NO) but not CA(NO). Plasma cortisol was significantly suppressed by oral prednisolone only.
Whilst CA(NO) remains a biomarker of interest in COPD, it is not suppressed by systemic or extra-fine particle ICS. CA(NO) is not a useful marker for monitoring response of small airway disease to therapies in COPD. The study was approved by the local Committee on Medical Research Ethics and registered on ClinicalTrials.Gov (NCT 00921921).