Normally, the pleural space, which is between the parietal and visceral pleurae, is only a potential space. Air or fluid in the space may compromise lung expansion. Blood in the pleural space can be associated with both hemorrhagic shock and respiratory compromise. It needs to be evacuated effectively to prevent complications of fibrothorax and empyema. Many of these patients had other severe extra thoracic injuries.
Nontraumatic hemothorax carries a much lower mortality.
Again, these statistics apply only to traumatic hemothorax. Occasionally, a hemorrhagic diathesis such as hemorrhagic disease of the newborn or Henoch-Schonlein purpura can lead to spontaneous hemothorax. Internal thoracic artery rupture has been reported in association with Ehlers-Danlos syndrome. A small fraction of patients with spontaneous pneumothorax will develop hemothorax. Findings include diminished ipsilateral breath sounds and a dull percussion note.