Spontaneous Pneumothorax

Spontaneous Pneumothorax

Persitent pneumothorax after chest tube placement.

CR – Large left pneumothorax without tension.

CT – Two apical blebs. Note the small residual pneumothorax and hazy and confluent pulmonary opacities.

Spontaneous pneumothorax is most often related to rupture of subpleural apical blebs. Symptoms include chest pain and shortness of breath but symptoms are usually mild; approximately 10% of patients are asymptomatic. Spontaneous pneumothorax occurs in upto 18 per 100,000 but is less common in females. A family history is elicited in 10%. Changes in atmospheric pressure and exposure to loud music have also been implicated.

The etiology of apical subpleural blebs is unknown but could be related to more negative pleural pressure at the apices which may cause a traction-effect on the adjacent lung. This pressure difference is more marked in taller patients. Smoking and other chronic lung disease (e.g., cystic fibrosis) lead to secondary damage and predispose to spontaneous pnumothorax. Shear stresses are increased at the apices which may also contribute to disruption of the subpleural blebs.

The main physiologic impact of pneumothorax is decrease in vital capacity and decrease in partial pressure of oxygen, both of which are well tolerated in young and otherwise healthy individuals. Delay in treatment of pneumothorax often results in reexpansion pulmonary edema (the hazy opacities in the left lung on this CT is likely related to reexpasion pulmonary edema).