Pathophysiology
Normally, the negative pressure within the pleura maintains lung inflation. When the pleura are injured, the negative pressure is lost, air enters the pleural space, and a portion of the lung is allowed to collapse. Ventilation and oxygenation may be compromised from the collapsed lung as pressure builds up within the pleural space (tension pneumothorax). The pressure can cause the mediastinum to shift toward the unaffected lung, the great vessels are compressed, and cardiac output decreases. If this is severe or not relieved quickly, complete cardiovascular collapse can occur.
PSP appears to be related to undiagnosed lung abnormalities such as:
Subpleural blebs and bullae are present by computed tomography (CT) or thoroscopic exam in up to 90% of cases (Havelock et al 2010)
A bleb or bullae may rupture (Buttero 2012; Parrillo & Dellinger 2007)
Emphysema-like changes, predominantly in the upper and peripheral regions (Parrillo & Dellinger 2007)
Porous pleura (Parillo & Dellinger 2007)
SSP is related to underlying diseases such as:
COPD
Cystic fibrosis
Infection such as Pneumocystis jiroveci is associated with spontaneous pneumothorax in patients living with human immunodeficiency virus (HIV)
Primary or metastatic lung malignancy
Traumatic pneumothorax may occur as a result of either penetrating or blunt chest trauma or iatrogenic causes such as:
Central venous catheter insertion
Surgery
Cardiopulmonary resuscitation
Mechanical ventilation