Systemic effects of chronic obstructive pulmonary disease.

Traditionally, chronic obstructive pulmonary disease (COPD) has been understood as a disease of the lungs, characterized by irreversible airflow limitation due to chronic bronchitis and/or emphysema. The latter are thought mainly to be the consequence of an excessive inflammatory response to tobacco smoking. Recently, several studies have shown that this pulmonary inflammation may also be detected in the systemic circulation, and that this systemic inflammation may have important clinical consequences. Most prominent among them is the loss of skeletal muscle mass that a significant percentage of patients with COPD will show during the course of their disease. This limits considerably their exercise capacity, jeopardizes their health status, and has a negative impact on their prognosis. Importantly, such prognostic value is independent of the degree of airflow obstruction and potentially reversible with appropriate therapy. This chapter summarizes available evidence supporting the concept that COPD is more than a lung disease (the systemic effects of COPD), and speculates on potential cellular mechanisms as future therapeutic targets.