Tension pneumothorax occurs when an injury to the chest allows air to enter the pleural cavity but not to escape. Air accumulates in the pleural space with each inspiration and as intrathoracic pressure increases, the lung collapses. The increased pressure then causes compression of the heart and great blood vessels toward the unaffected side as evidenced by a mediastinal shift and distended neck veins. Cardiac output falls significantly producing signs and symptoms of shock (see the diagram below). 

Tension pneumothorax may be the immediate result of primary traumatic injury, a delayed complication of an occult injury such as bronchial tear, or the undesired complication of necessary therapies such as mechanical ventialtion.

Hallmark signs and symptoms of a tension pneumothorax include: 

• Anxiety 

• Rapid, Labored breathing 

• Distended Neck Veins 

• Tracheal Deviation from the Midline 

• Weak Pulse 

• Rapidly Falling Blood Pressure 

• Subcutaneous Emphysema 

• Diminished Breath Sounds on the Affected Side 

• Muffled Heart Tones