A pneumothorax requires a pathway for air or gas to reach the pleural space and a cause.
Routes for reaching the pleural space:
(1) across the chest wall
(2) across the lung
(3) across the diaphragm (via diaphragmatic foramina)
(4) via head, neck and mediastinal structures
Mechanisms for air being introduced:
(1) physical trauma (rib fracture, penetrating trauma)
(2) barotrauma (blast injury, positive pressure ventilation)
(3) iatrogenic injury (central venous catheterization, transthoracic needle biopsy, surgery, intubation)
(4) insufflation within the peritoneum or retroperitoneum
(5) rupture of a lung cyst (emphysema, apical cyst)
(6) bronchopleural fistula
If no cause is found then the pneumothorax is termed spontaneous.
