Chronic Obstructive Pulmonary Disease

COPD Overview - Breathless Beginnings

• Chronic, progressive disease with persistent airflow obstruction; largely irreversible. Diagnosis: post-bronchodilator FEV1/FVC < 0.7.
• Key Phenotypes:
  • Chronic Bronchitis (Clinical): Productive cough ≥ 3 months/yr for ≥ 2 consecutive yrs. "Blue bloaters".
  • Emphysema (Pathological): Alveolar wall destruction; permanent distal airspace enlargement. "Pink puffers".
• Risk Factors: Smoking (dominant), air pollution, occupational exposure, α1-antitrypsin deficiency (AATD).

⭐ Reid Index (mucous gland to bronchial wall thickness ratio) > 0.4 characterizes chronic bronchitis.

CXR Findings - COPD's Shadow Play

CXR reveals key signs, especially in emphysema-dominant COPD:

• Hyperinflation Signs:
  • Flattened hemidiaphragms (most reliable).
  • Increased retrosternal space (> 2.5 cm, lateral CXR).
  • Widened intercostal spaces.
  • Long, narrow, vertical heart.
• Parenchymal Changes (Emphysema):
  • Hyperlucency of lung fields.
  • Paucity of peripheral vascular markings (oligemia).
  • Bullae/blebs (lucent areas > 1 cm, thin walls).
• Chronic Bronchitis ("Dirty Lungs"):
  • CXR often normal or non-specific.
  • Increased bronchovascular markings (tram-tracks).
  • Thickened bronchial walls.
  • Cardiomegaly (cor pulmonale in advanced disease).

⭐ Saber-sheath trachea (coronal narrowing, sagittal widening of intrathoracic trachea) is a specific, though insensitive, sign of COPD.

HRCT Imaging - COPD's Sharp Focus

HRCT: Key for detailed COPD lung assessment, identifying emphysema and airway changes.

Emphysema Subtypes:

Airways Disease:

• Bronchial Wall Thickening (BWT):
  • Normal: < 1.5 mm or BWT/diameter ratio < 0.25.
  • COPD: ↑ BWT (> 2 mm), bronchial dilatation.
• Air Trapping (Expiratory HRCT):
  • ↓Attenuation areas (lucent) not increasing density on expiration.
  • Mosaic pattern.
• Other: Mucous plugging.

Associated Findings:

• Saber-sheath trachea.
• Pulmonary HTN signs (MPA diameter > 29 mm or MPA/Aorta ratio > 1).

⭐ Centrilobular emphysema: most common in smokers, shows upper lobe predominant lucencies on HRCT.

COPD Complications - When Lungs Cry Foul

• Pulmonary Hypertension (PHT):
  • Signs: Main pulmonary artery (MPA) diameter > 29mm (CT), RV hypertrophy, peripheral pruning.
• Acute Exacerbations (AECOPD):
  • Imaging: ↑ Bronchial wall thickening, new/worsening consolidation, ↑ air trapping.
• Spontaneous Pneumothorax:
  • Cause: Ruptured bullae/blebs.
  • Sign: Visceral pleural line, absent lung markings peripherally.
• Cor Pulmonale:
  • Sequela: RV enlargement & dysfunction due to PHT.
• Lung Cancer:
  • ↑ Risk, especially in emphysematous areas.

⭐ Pulmonary artery to aorta (PA:A) ratio > 1 on CT is a common indicator of pulmonary hypertension in COPD patients, often seen alongside MPA diameter > 29mm.

High‑Yield Points - ⚡ Biggest Takeaways

• COPD is defined by persistent, irreversible airflow limitation, predominantly caused by cigarette smoking.
• Chest X-ray findings include hyperinflation, flattened hemidiaphragms, and an increased retrosternal space.
• HRCT is superior for detecting emphysema (centrilobular, panlobular, paraseptal) and bronchial wall thickening.
• Common complications are pulmonary hypertension and cor pulmonale.
• Alpha-1 antitrypsin deficiency is linked to early-onset panlobular emphysema, typically in lower lung zones.
• Presence of bullae, blebs, and saber-sheath trachea are notable signs.