Airflow obstruction is caused in COPD by two mechanisms.
Bronchiolitis, with pathologic changes of inflammation, fibrosis,
luminal mucus, and muscle hypertrophy and contraction is one mechanism.
This mechanism is partially reversible. The other mechanism is the loss
of lung elastic recoil and rupture of alveolar attachments to small,
poorly supported airways. In inspiration, these airways are held open.
However as lung volume decreases, these airways collapse at a lung
volume much above the point of small airway closure in normal persons.
Some years ago, I concluded from a review of the literature that, early
in the course of COPD, airflow obstruction was due primarily to
bronchiolitis. Late in the course of the disease, emphysema assumed
much greater prominence. The CT study reported at this meeting by
Stanescu and colleagues supports that concept. However, it is clear
that a crossectional study of persons with varying degrees of airflow
obstruction due to COPD, or preferably, a longitudinal study using CT,
will be needed to definitively answer this question.