• Presence of free air in the intrapleural space
  • Spontaneous pneumothorax is due to atraumatic rupture of alveolus, bronchiole, or bleb
  • Primary spontaneous pneumothorax (2/3 of incidences):
    • No underlying pulmonary pathology present
    • Rupture of small subpleural cyst or bleb
    • Primarily young, healthy patients (20–40 yr old) with tall, thin body habitus
    • Risk factors: Smoking, family history, Marfan syndrome, homocystinuria, thoracic endometriosis
    • Evidence of possible increased incidence with changes in weather pattern/atmospheric pressure
  • Secondary spontaneous pneumothorax from underlying pulmonary pathology (see Etiology)
  • Tension pneumothorax:
    • Air continues to enter pleural space through bronchoalveolar disruption and becomes trapped via “ball-valve” mechanism
    • Intrapleural pressure increases
    • Venous return to right heart decreases, resulting in decrease in cardiac output
    • Mediastinum shifts toward uninvolved side, mechanically interfering with right atrial filling
    • Ventilation compromise and ventilation/perfusion mismatch result in hypoxemia


  • Idiopathic
  • Airway disease:
    • Chronic obstructive pulmonary disease (COPD)
    • Asthma
    • Cystic fibrosis
  • Infections:
    • Necrotizing bacterial pneumonia
    • TB
    • Fungal pneumonia
    • Pneumocystis carinii
  • Neoplasm
  • Interstitial lung disease:
    • Sarcoidosis
    • Idiopathic pulmonary fibrosis
    • Lymphangiomyomatosis
    • Tuberous sclerosis
    • Pneumoconioses
  • Connective tissue diseases
  • Pulmonary infarction
  • Endometriosis
  • Blunt chest trauma
  • Penetrating trauma to neck or trunk
  • Iatrogenic:
    • Central line placement
    • Other vascular access procedures

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