Pathophysiology of Chronic Bronchitis (COPD)
Chronic Obstructive Pulmonary Disease (COPD) is a disease characterized by airflow limitation that is not fully reversible. Airflow limitation is usually progressive and associated with an inflammatory response in the lungs stimulated by irritants. COPD includes chronic bronchitis and pulmonary emphysema. Although sometimes included in COPD, asthma is a reversible disorder and is therefore considered elsewhere.
Chronic bronchitis is chronic inflammation of the lower airways characterized by excessive secretion of mucus, hypertrophy of mucous glands, and recurring infection, progressing to narrowing and obstruction of airflow. Emphysema is the enlargement of the air spaces distal to the terminal bronchioles, with breakdown of alveolar walls and loss of elastic recoil of the lungs. The two conditions may overlap, resulting in subsequent derangement of airways dynamics (e.g., obstruction to airflow). In pulmonary emphysema, lung function progressively deteriorates for many years before the illness becomes apparent.
The most common cause of COPD is cigarette smoking. Air pollution, occupational exposures, allergens, and infections may also act as irritants. Alpha1-antitrypsin deficient is an infrequent cause. Complications include respiratory failure, pneumonia or other overwhelming respiratory infection, right heart failure (cor pulmonale), arrhythmias, and depression.