Pathophysiology of obstructive airways disease.

Chronic obstructive pulmonary disease is a group of disorders that have in common abnormal airway structure that results in obstruction to airflow. In emphysema, obstruction is thought to be due to the loss of normal elastic tension in the lung parenchyma. Cigarette smoke is the most important cause of emphysema. Injurious agents, either in the gas or particulate phase, incite a proteolytic reaction in the lung. The type of emphysema and its topographic distribution in the lung stem from normal physiologic processes that concentrate the cigarette puff both within the lung and within the secondary pulmonary lobule.