Possible role of airway microvascular permeability on airway obstruction in patients with chronic obstructive pulmonary disease

Background: Airway microvascular system participates in the airway inflammation that is central to the pathophysiology of inflammatory lung disorders. Objective: To examine the role of airway microvascular permeability on airway obstruction in patients with chronic obstructive pulmonary disease (COPD). Methods: We measured the airway microvascular permeability index (AMPI) separately in the central or peripheral airways using a bronchoscopic microsampling technique in 9 non-smokers, 18 smokers without COPD (10 former smokers and 8 current smokers), and 26 smokers with COPD (12 former smokers and 14 current smokers). Results: AMPI in the central airways was relatively low, and this index was comparable among the five groups. In contrast, AMPI in the peripheral airways was significantly higher in smokers with or without COPD compared with non-smokers. Moreover, AMPI in the peripheral airways was significantly higher in current smokers than in former smokers with COPD. Especially, AMPI in the peripheral airways, but not in the central airways, showed a significant correlation with the degree of airway obstruction in former or current smokers with COPD. However, AMPI in the peripheral airways was not correlated with the diffusing capacity of the lung in former or current smokers with COPD. Conclusion: Airway microvascular permeability in the peripheral airways is increased in patients with COPD, and is associated with the severity of airway obstruction. We may need to consider this characteristic feature as a target in any therapeutic strategy for the treatment of the disease.