What is a tension pneumothorax?
Uncommonly, gas in the pleural space can develop positive pressure, most often as a result of mechanical ventilation, and can compress the mediastinum with resultant decreased venous return to the heart. This can be a medical emergency because rapid cardiopulmonary compromise and death may ensue if the patient is not immediately treated. The radiographic clues to a tension pneumothorax are the presence of a pneumothorax in association with contralateral mediastinal shift and inferior displacement of the ipsilateral hemidiaphragm ( Figure 21-3 ). These findings are not diagnostic of a tension pneumothorax, however, which can occur without these findings. The diagnosis is based on radiographic recognition of a pneumothorax and clinical findings of hypotension and tachycardia. Immediate decompression by thoracentesis through the second rib interspace in the midclavicular line or with chest thoracostomy is typically performed for emergent treatment of a tension pneumothorax.