Abnormal collection of free air or gas in the pleural space


Depends on the underlying lung disease


  • Spontaneous pneumothorax
    • Male > female (1.4 to 10.1:1)
    • Peak incidence: 10 to 30 years
  • Pneumothorax with cystic fibrosis (CF)
    • For overall CF population: 3.5–8%
    • CF patients >18 years: 16–20%
    • Risk factors for pneumothorax:
      • More severe disease
      • Decreased pulmonary function (i.e., forced expiratory volume in 1 second [FEV1] <30–50%)
      • Colonization with Pseudomonas aeruginosa, Burkholderia cepacia, or Aspergillus

Risk Factors

  • Asthma
  • CF
  • Pneumonia
  • Collagen vascular diseases


  • Air can enter the pleural space via the following:
    • Chest wall (i.e., penetrating trauma)
    • Intrapulmonary (i.e., ruptured alveoli)
  • Usually, collapse of the lung on the affected side seals the leak.
  • If a ball valve mechanism ensues, however, air can accumulate in the thoracic cavity, causing the development of a tension pneumothorax (a medical emergency).


  • Spontaneous (secondary to rupture of apical blebs)
  • Mechanical trauma
    • Penetrating injury (i.e., knife or bullet wound)
    • Blunt trauma (i.e., auto accident)
  • Barotrauma
    • Mechanical ventilation
    • Cough (if severe enough)
    • Vaginal birth
  • Iatrogenic
    • Central venous catheter placement
    • Bronchoscopy (especially with biopsy)
  • Infection: most common organisms
    • Staphylococcus aureus
    • Streptococcus pneumoniae
    • Mycobacterium tuberculosis
    • Bordetella pertussis
    • Pneumocystis jiroveci
  • Airway occlusion
    • Mucus plugging (asthma)
    • Foreign body
    • Meconium aspiration
  • Bleb formation (i.e., idiopathic, secondary to CF)
  • Malignancy
  • Catamenial

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