Remember that a pneumothorax normally is not a life-threatening injury, but a tension pneumothorax is life-threatening. As intrathoracic pressure increases, casualties develop hypotension, jugular vein distention (JVD), and tracheal deviation. The affected hemithorax is hyper-resonant to percussion and often feels tense, mildly distended, and hard to compress on palpation. Some people compare the chest to the feeling of pressing a fully inflated football.

Signs of tension pneumothorax include early and late signs. The early signs and symptoms to look for relate to significant torso trauma or primary blast injury and commonly include:

### Early Signs

- Severe or progressive respiratory distress
- Severe or progressive tachypnea – abnormally rapid breathing
- Absent or markedly decreased breath sounds on one side of the chest
- Hemoglobin oxygen saturation < 90% on pulse oximetry
- Shock – If not treated promptly, tension pneumothorax may progress from respiratory distress to shock and traumatic cardiac arrest.
- Traumatic cardiac arrest without obviously fatal wounds

### Late Signs

- Tracheal deviation
- Jugular vein distention
- Subcutaneous emphysema
- Shift of the mediastinal contents away from the side of the tension pneumothorax

The late signs may not be displayed or may be displayed only when the casualty’s condition has worsened. Late signs that indicate the progression of tension pneumothorax include JVD from the mechanical obstruction of blood flow returning to the heart; tracheal deviation (a shift of the windpipe to the right or left); and tachycardia, as the body attempts to push more blood to the lungs to be oxygenated.