Definition
Chronic obstructive pulmonary disease is a progressive, irreversible, obstructive lung disease characterized by persistent respiratory symptoms and airflow limitation, which is not fully reversible even after bronchodilator use. It includes:
- Pulmonary emphysema: alveolar wall destruction and distal airspace enlargement
- Chronic obstructive bronchitis: chronic productive cough due to mucus hypersecretion and inflammation
Both conditions often coexist, and patients usually present with overlapping features.
Pulmonary Emphysema
Definition
Emphysema is defined as the abnormal, permanent enlargement of airspaces distal to terminal bronchioles, accompanied by destruction of alveolar walls and capillaries, without significant fibrosis. This leads to air trapping, reduced surface area for gas exchange, and hyperinflated lungs.
Etiology
- Smoking – chronic exposure leads to neutrophil activation and protease release, damaging alveolar walls
- α1-antitrypsin deficiency – inherited condition causing lack of protection from elastase → early-onset emphysema
- Can also occur as a complication of chronic bronchitis, bronchiectasis, or asthma due to long-standing airway inflammation
Symptoms
- Progressive dyspnea, first on exertion and later at rest – due to loss of elastic recoil and ventilation-perfusion mismatch
- Mild cough, with minimal sputum – not a major feature
- Fatigue, decreased exercise tolerance (from poor oxygenation and increased work of breathing)
- Dyspnea is not relieved in sitting position (distinguishes it from cardiac dyspnea)
Physical Examination
- Barrel chest – caused by chronic air trapping and hyperinflation
- Short neck, sometimes prominent neck veins due to accessory muscle use
- Use of accessory respiratory muscles, often seen during even mild activity
- Decreased vocal fremitus, hyperresonant percussion – due to overinflated lungs
- Decreased vesicular breath sounds, prolonged expiration, often with snoring or whistling wheezes
- In advanced disease: central cyanosis and polycythemia from chronic hypoxia.
- Pink Puffer
Lab Tests
- Decreased Hemoglobin, RBC, and hematocrit – from secondary polycythemia due to long-standing hypoxia
- Decreased ESR – thickened blood from polycythemia slows sedimentation
- Sputum testing only if infection is suspected
Instrumental Tests
- Chest X-ray:
- Hyperinflated lungs
- Flattened diaphragm
- Widened intercostal spaces
- ↑ Retrosternal air space
- May show ↑ lung markings if coexisting bronchitis is present
- Spirometry:
- Obstructive pattern: ↓ FEV1, ↓ FEV1/FVC (<70%)
- Not significantly reversible with bronchodilators
- Shows difficulty in exhalation due to alveolar collapse
- Blood gases:
- Hypoxemia (↓ pO₂) and hypercapnia (↑ pCO₂) due to poor gas exchange
- ↓ O₂ saturation especially in advanced cases
Complications
- Right-sided heart failure (cor pulmonale) – from chronic hypoxic vasoconstriction causing pulmonary hypertension
- Pneumothorax – may occur if alveolar bullae rupture
- Frequent respiratory infections – due to poor airway clearance