Tension Pneumothorax

Tension pneumothorax is a life-threatening condition caused by the continuous entrance and entrapment of air into the pleural space, thereby compressing the lungs, heart, blood vessels, and other structures in the chest. The pleura is a double-layered membrane that lines the inner part of the chest wall and the surface of the lungs, allowing them to move and slide together during respiration. The two layers of the pleura fold onto each other, forming the pleural space. Under normal conditions, the pleural space contains a thin layer of fluid that prevents the two layers of the pleura from rubbing against each other. 

When there's damage to the pleura, either due to lung disease or trauma to the chest wall, air from the outside or from the lungs can flow freely into the pleural space, but cannot leave. The accumulated air in the pleural space puts positive pressure on the lung and prevents it from expanding properly, which causes respiratory distress. As the air continues to accumulate, the trachea and other structures of the chest can be pushed away from the pneumothorax, leading to increased difficulty breathing. Additionally, the increased pressure inside the chest can compress the heart and lead to a collapse of the blood vessels that drain to the heart, in turn decreasing venous return and cardiac output. If left untreated, tension pneumothorax can rapidly progress to cardiovascular collapse, which ultimately leads to cardiac arrest.

Tension pneumothorax can develop from any type of pneumothorax. However, it is most commonly seen after a traumatic chest injury or in individuals breathing through mechanical ventilation. 

• Traumatic tension pneumothorax 

  • Open chest wound, like a stab wound or a gunshot 

  • Closed trauma, like a rib fracture

• Mechanical ventilation 

  • High positive pressure during the inspiratory phase can force air from the lungs into the pleural space, causing a rapidly growing pneumothorax. 

  • Rarely, a spontaneous tension pneumothorax can occur in the absence of any precipitating factors.

• Symptoms

  • Severe shortness of breath

  • Shallow breathing

  • Acute chest pain

• Signs

  • Low blood oxygen levels

  • Increased heart rate

  • Low blood pressure

  • Altered mental status

• Clinical findings 

  • Tracheal deviation away from the affected side 

  • Decreased or absent breath sounds upon lung auscultation

  • Hyperresonant chest percussion

  • Asymmetrical expansion of the chest due to the collapsed affected lung 

• In severe cases: 

  • Blue discoloration of the skin due to decreased oxygen levels in the blood

  • Distended neck veins as a result of the collapsed blood vessels that should return blood to the heart 

  • Sometimes, the air in the pleural space can leak and be trapped in nearby areas, such as the subcutaneous tissue, which is known as subcutaneous emphysema, as well as nearby cavities like the mediastinum, causing a pneumomediastinum. 

• Clinical evaluation

  • Diagnosis of tension pneumothorax should be suspected in individuals with respiratory distress, tracheal deviation, distended neck veins, low blood pressure, and decreased or absent breath sounds upon lung auscultation. 

  • A strong clinical suspicion of tension pneumothorax is enough to initiate emergency treatment, which should not be delayed by any imaging studies.

• Once the individual has been successfully treated, imaging can be performed. 

  • Chest X-ray 

    • Radiological signs of pneumothorax in general can include increased transparency or radiolucency of the affected side, increased rib separation, and partial or total collapse of the affected lung. 

    • More specific radiological signs for tension pneumothorax includes mediastinal and tracheal deviation away from the pneumothorax, as well as flattening of the diaphragm. 

  • A point-of-care ultrasound can also be used to confirm the diagnosis. 

Tension pneumothorax is a medical emergency that requires immediate treatment. 

• Needle decompression of the chest, also known as needle thoracostomy, to allow the relief of the trapped air from the pleural space. 

  • During needle decompression, an emergency technician or trained physician will insert a large needle through the chest wall, in between the ribs, and into the pleural space. This procedure can be life-saving, especially in the prehospital setting, as transport to the hospital can delay treatment. 

  • After needle decompression, the inserted needle is left in place until a more definitive chest tube can be placed to facilitate the relief of the remaining air. After placing the chest tube, a chest X-ray is usually obtained to check the location of the tube and the successful re-expansion of the lung. 

• Monitoring in a critical care unit to oversee vital signs and administer high-concentration supplemental oxygen. 

What is the difference between pneumothorax and tension pneumothorax?

Pneumothorax occurs when there’s a defect in the pleura that allows air to leak into the pleural space, causing the partial or total collapse of the affected lung. The air trapped does not, however, continue accumulating, and some of the air is also able to escape during expiration. As a result, the intrapleural pressure does not keep increasing, which allows the affected lung to partially expand and fill with oxygen during inspiration. 

Depending on the cause, pneumothorax can be classified as spontaneous or traumatic. Spontaneous or simple pneumothorax can be further subdivided into primary spontaneous pneumothorax (in absence of an underlying lung disease) or secondary spontaneous pneumothorax (if resultant from an underlying lung disease). On the other hand, traumatic pneumothorax can result from any kind of trauma to the chest; this includes iatrogenic pneumothorax, which occurs as a complication of a medical procedure. 

Both spontaneous and traumatic pneumothorax can evolve into tension pneumothorax, which is a life-threatening condition that can lead to significant respiratory distress and hemodynamic instability. In tension pneumothorax, the pleural injury acts as a one-way valve. As a result, the air can enter the pleural space during inspiration, but is unable to escape during expiration. With each inhalation, more air gets trapped inside the chest, leaving less space for the lungs to expand.