Pneumothorax ex vacuo

Pneumothorax ex vacuo is an uncommon complication of lobar lung collapse, particularly right upper lobe collapse.

Clinical presentation

Patients are usually asymptomatic ³. 

Pathology

Acute bronchial obstruction for any reason, such as bronchogenic carcinomas, mucus plugs, foreign bodies, or malpositioned endotracheal tubes, can cause acute lobar collapse and a marked increase in negative intrapleural pressure around the collapsed lobe which results in gas - that is, nitrogen from surrounding tissues and blood vessels - being drawn into the pleural space around the collapsed lobe while the seal between the visceral and parietal pleura around aerated lobes remains intact.

It is also seen following removal of pleural effusion by thoracentesis when the collapsed lung struggles to re-expand. It is thought that this type of ex vacuo pneumothorax occurs because (a) co-existing pleural disease precludes normal re-expansion of the lung ⁶ or (b) pulmonary surfactant production is insufficient due to pulmonary edema, decreased blood flow and chronic atelectasis ^4,5.

Radiographic features

See article on pneumothorax. Also, there may be signs of lobar lung collapse.

Treatment and prognosis

The pneumothorax spontaneously resolves when the bronchial obstruction is relieved and the lobe re-expands. The noncompliant lung is usually unresponsive to chest drain insertion and so it should not be used in asymptomatic patients unless there is a concern for trapped lung ^5,7,8.