Airflow pattern complexity during resting breathing in patients with COPD: Effect of airway obstruction

• We investigated the influence of obstruction in the airflow pattern complexity in COPD.
• We examine the use of complexity measurements as a marker of disease activity.
• The airflow pattern complexity was reduced proportionally to airway obstruction.
• The early adverse effects of COPD were detected with an accuracy of 84%.
• Complexity analysis may provide novel biomarkers to the diagnosis of COPD.

We investigated the influence of airway obstruction in the complexity of the airflow pattern in COPD and its use as a marker of disease activity. The sample entropy (SampEnV′) and the variability (SDV′) of the airflow pattern were measured in a group of 88 subjects with various levels of airway obstruction. Airway obstruction resulted in a reduction in the SampEnV′ (p < 0.0001) that was significantly correlated with spirometric indices of airway obstruction (R = 0.50, p < 0.001). The early adverse effects in mild airway obstruction were detected by the SampEnV′ with an accuracy of 84%. SDV′ increased with airway obstruction (p < 0.002). We conclude that (1) the airflow patterns in COPD exhibit reduced complexity compared with healthy subjects; (2) this reduction in complexity is proportional to airway obstruction; and (3) the evaluation of SampEnV′ may provide novel respiratory biomarkers suitable to facilitate the diagnosis of respiratory abnormalities in COPD.