Obstructive lung diseases (chronic bronchitis, emphysema) - etiology, pathogenesis, and clinical manifestations.
Group of diseases characterized by increased airway resistance, leading to obstructed airflow, especially during expiration.
I. Chronic bronchitis
Etiology
- Cigarette smoking (most common cause).
- Air pollution, occupational dust and chemical exposure.
- Recurrent respiratory infections.
Pathogenesis
- Chronic exposure to irritants → airway epithelial irritation.
- Mucous gland hyperplasia and goblet cell metaplasia → excessive mucus production.
- Impaired ciliary function → decreased mucus clearance.
- Airway narrowing and obstruction by thick mucus → air trapping.
- Chronic inflammation → fibrosis and smooth muscle hypertrophy.
Clinical manifestations
- Chronic productive cough ("blue bloater").
- Dyspnea on exertion (later stages).
- Frequent respiratory infections.
- Cyanosis (hypoxemia).
- Peripheral edema (due to right heart failure — cor pulmonale).
II. Emphysema
Etiology
- Smoking (major cause).
- α₁- antitrypsin deficiency (genetic form).
Pathogenesis
- Inflammation and oxidative stress from smoking → activation of neutrophils and macrophages.
- Release of proteases (elastase) and reactive oxygen species → destruction of alveolar walls.
- Loss of elastic recoil and alveolar septa → permanent enlargement of airspaces distal to terminal bronchioles.
- Air trapping → hyperinflation → impaired expiratory airflow.
- Decreased alveolar surface area → impaired gas exchange.
Clinical manifestations
- Progressive dyspnea ("pink puffer").
- Minimal cough and scant sputum.
- Weight loss (increased work of breathing).
- Barrel- shaped chest (hyperinflation).
- Use of accessory muscles.
- Pursed- lip breathing (to prevent airway collapse).