(See also Overview of Thoracic Trauma Overview of Thoracic Trauma Thoracic trauma causes about 25% of traumatic deaths in the US. Many chest injuries cause death during the first minutes or hours after trauma; they can frequently be treated at the bedside... read more .)
Tension pneumothorax develops when a lung or chest wall injury is such that it allows air into the pleural space but not out of it (a one-way valve). As a result, air accumulates and compresses the lung, eventually shifting the mediastinum, compressing the contralateral lung, and increasing intrathoracic pressure enough to decrease venous return to the heart, causing shock Shock Shock is a state of organ hypoperfusion with resultant cellular dysfunction and death. Mechanisms may involve decreased circulating volume, decreased cardiac output, and vasodilation, sometimes... read more . These effects can develop rapidly, particularly in patients undergoing positive pressure ventilation.
Causes include mechanical ventilation (most commonly) and simple (uncomplicated) pneumothorax Pneumothorax Pneumothorax is air in the pleural space causing partial or complete lung collapse. Pneumothorax can occur spontaneously or result from trauma or medical procedures. Diagnosis is based on clinical... read more 
with lung injury that fails to seal following penetrating or blunt chest trauma or failed central venous cannulation.
Symptoms and Signs of Tension Pneumothorax
Symptoms and signs initially are those of simple pneumothorax Pneumothorax Pneumothorax is air in the pleural space causing partial or complete lung collapse. Pneumothorax can occur spontaneously or result from trauma or medical procedures. Diagnosis is based on clinical... read more . As intrathoracic pressure increases, patients develop hypotension, tracheal deviation, and neck vein distention. The affected hemithorax is hyperresonant to percussion and often feels somewhat distended, tense, and poorly compressible to palpation.
Diagnosis of Tension Pneumothorax
Clinical evaluation
Tension pneumothorax should be diagnosed by clinical findings. Treatment should not be delayed pending radiographic confirmation. Although cardiac tamponade Cardiac Tamponade Cardiac tamponade is accumulation of blood in the pericardial sac of sufficient volume and pressure to impair cardiac filling. Patients typically have hypotension, muffled heart tones, and distended... read more also can cause hypotension, neck vein distention, and sometimes respiratory distress, tension pneumothorax can be differentiated clinically by its unilateral absence of breath sounds and hyperresonance to percussion.
Treatment of Tension Pneumothorax
Needle decompression followed by tube thoracostomy
Treatment of tension pneumothorax is immediate needle decompression by inserting a large-bore (eg, 14- or 16-gauge) needle into the 2nd intercostal space in the midclavicular line. Air will usually gush out. Because needle decompression causes a simple pneumothorax, tube thoracostomy should be done immediately thereafter.
