Differential Clinical Significance of FENO and CANO in Asthma, Chronic Obstructive Pulmonary Disease (COPD), and Asthma-COPD Overlap (ACO).

PURPOSE

To investigate the differential clinical significance of fractional concentration of exhaled nitric oxide measured at a flow rate of 200 mL/s (FENO) and concentration of nitric oxide in alveolar (CANO) in asthma, chronic obstructive pulmonary disease (COPD) or asthma-COPD Overlap (ACO).

METHODS

A total of 178 patients were included, with 82 patients in asthma group, 47 patients in COPD group and 49 patients in ACO group. Data for demographic data, spirometry and exhaled nitric oxide were collected for comparative analysis, correlation analysis and discriminant canonical analysis.

RESULTS

The values of FENO in asthma, COPD and ACO groups were 11.0(7.0-22.3), 8.0(6.0-11.0) and 9.0(6.5-19.5) ppb, respectively. In the asthma group, FENO exhibited negative correlations with FEV/FVC, MMEF and MEF50. No significant correlation was observed between CANO and pulmonary function parameters. In the COPD group, both FENO and CANO showed negative correlation with pulmonary function parameters including FVC, FEV, PEF, MMEF, MEF75, MEF50. In the ACO group, FENO demonstrated no significant correlation with pulmonary function parameters, while CANO was correlated with FEV, PEF, MMEF and MEF50. In COPD group, ΔFEV in the bronchodilator test was correlated with FENO. As for the ACO group, ΔFEV was correlated with CANO. In the discriminant canonical analysis, four parameters including gender, age, MEF75 and FENO discriminated between the three groups of asthma, COPD and ACO.

CONCLUSION

In asthma, COPD and ACO, FENO has demonstrated a robust correlation with CANO. Elevated FENO levels are predominantly indicative of pulmonary function impairment in asthma and COPD, whereas elevated CANO levels are mainly correlated with pulmonary function impairment in COPD and ACO. Compared with FENO and CANO, FENO may have a better discriminatory ability in distinguishing asthma, COPD and ACO.