((((airflow OR airway* OR lung[tiab] OR lungs[tiab] OR bronchopulmon* OR bronchi OR bronchitic OR bronchial OR respiratory OR bronchiti*) AND obstruct*) AND chronic) OR emphysem* OR COAD OR COPD OR "Pulmonary Disease, Chronic Obstructive"[Mesh])
The above is based, in large part, on the COPD keyword strategy that Lorie Kloda has posted on this blog.
