Pathogenesis and pathology of COPD.

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation. Since flow is the result of a driving pressure that promotes flow and of an opposing resistance that contradicts it, the reduction in flow observed in COPD has two main components: increased resistance, which is due to airway obstruction, and a loss of the elastic recoil pressure of the lung, which is due to parenchymal destruction. Although it has long been known that the major site of increased resistance in COPD is the peripheral airways, recent studies have shown that central airways are involved in the disease as well. The purpose of this review is to describe the major structural and cellular changes present in peripheral airways, central airways and lung parenchyma of patients with COPD, and to underline the possible mechanisms contributing to airflow limitation in these subjects.