DESCRIPTION

Abnormal collection of free air or gas in the pleural space

EPIDEMIOLOGY

Depends on the underlying lung disease

ETIOLOGY

• 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)
  • Valsalva maneuver
  • 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: a spontaneous and often recurrent pneumothorax in women of reproductive age that has a temporal relationship with menstruation; it may be secondary to the ectopic implantation of endometrial tissue within the thorax.

RISK FACTORS

• Asthma
• CF
• Pneumonia
• Collagen vascular diseases

PATHOPHYSIOLOGY

• 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).