Reduced Airway Distensibility, Fixed Airflow Limitation, and Airway Wall Remodeling in Asthma

The airways of individuals with asthma are less distensible than normal and it has been assumed that this may be due to airway remodeling associated with chronic inflammation, although there are currently no available data directly relating these two aspects of asthma. We have therefore carried out a study of the relationship between airway distensibility (ΔVD) and subepithelial reticular basement membrane (RBM) thickening as an index of airway remodeling, in a group of patients with relatively mild but symptomatic asthma. Our methods included a cross-sectional study of ΔVD in patients with mild to moderate atopic asthma, with matched airway biopsy for structural components. We confirmed that ΔVD was lower in patients with asthma than in normal individuals (19.8 ± 1.1 versus 24.1 ± 1.5; p < 0.05) and that RBM thickness was increased in patients with asthma (9.1 ± 2.2 versus 7.7 ± 1.2 μm; p < 0.01). There was a negative correlation between ΔVD and RBM thickness in asthma (r = -0.37, p = 0.03) and positive correlations between percent predicted postbronchodilator large and small airway function (for percent predicted FEV 1 versus ΔVD, r = 0.59, p < 0.001). We conclude that, cross-sectionally, ΔVD was related to airway remodeling (RBM thickening) and airflow limitation (percent predicted large and small airway function). Our findings support the hypothesis that ΔVD is a physiologic test that is reflective of airway remodeling.