FEV1/FVC ≤0.7 FEV1≤75% of predicted with at least 10% decline from baseline, no significant post-bronchodilator response Additional evidence of small-airway disease (at least 1 out of 3)
Evidence of air trapping, small-airway thickening or bronchiectasis on high-resolution computed tomography of chest (with inspiratory and expiratory cuts) Residual volume 120%, or elevated residual volume/total lung capacity Pathologic confirmation of constrictive bronchiolitis
Absence of infection in the respiratory tract
By appropriate clinical, radiologic, microbiologic studies (sinus aspiration, upper respiratory tract, viral screen, sputum culture or bronchoalveolar lavage)
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