Alveolar and Bronchial Nitric Oxide in Chronic Obstructive Pulmonary Disease and Asthma–COPD Overlap

Introduction Exhaled nitric oxide (FENO) measurements differentiate COPD phenotypes from asthma–COPD overlap (ACO). To date, no study has been conducted to determine whether alveolar and bronchial components differ in this group of patients. Methods This was an observational cross-sectional study recruiting ambulatory COPD patients. FENO was measured, differentiating alveolar (CANO) from bronchial (JawNO) components using a multiple-flow technique. CANO and JawNO values were compared between eosinophilic COPD patients (defined as ≥300 eosinophils/μL in peripheral blood test, or ≥2% eosinophils or ≥3% eosinophils), and a linear regression analysis was performed to determine clinical and biological variables related to these measurements. Results 73 COPD patients were included in the study. Eosinophil counts were associated with increased values of CANO and JawNO (for the latter only the association with ≥300 or ≥3% eosinophils was significant). CANO was also associated with CRP, and JawNO with smoking. Conclusions Patients with COPD and ACO characteristics show increased inflammation in the large and small airways. CANO and JawNO are associated with clinical and biological variables.