How to Relieve a Tension Pneumothorax in the Pre-Hospital Setting

Tension pneumothorax is the progressive build-up of air within the pleural space, usually due to a lung laceration which allows air to escape into the pleural space but not to return. Positive pressure ventilation may exacerbate this 'one-way-valve' effect. Progressive build-up of pressure in the pleural space pushes the mediastinum to the opposite hemithorax, and obstructs venous return to the heart. This leads to circulatory instability and may result in traumatic arrest.

Diagnosis

The classic signs of a tension pneumothorax are deviation of the trachea away from the side with the tension, a hyper-expanded chest, an increased percussion note and a hyper-expanded chest that moves little with respiration. The central venous pressure is usually raised, but will be normal or low in hypovolaemic states.

 

Management

Needle Thoracostomy

Classical management of tension pneumothorax is emergent chest decompression with needle thoracostomy. A 14-16G intravenous cannula is inserted into the second rib space in the mid-clavicular line. The needle is advanced until air can be aspirated into a syringe connected to the needle. The needle is withdrawn and the cannula is left open to air. An immediate rush of air out of the chest indicates the presence of a tension pneumothorax. The manoeuver essentially converts a tension pneumothorax into a simple pneumothorax.

Many texts will state that a tension pneumothorax is a clinical diagnosis and should be treated with needle thoracostomy prior to any imaging. Recently this dogma has been called into question. Needle thoracostomy is probably not as benign an intervention as previously thought, and often is simply ineffective in relieving a tension pneumothorax. If no rush of air is heard on insertion, it is impossible to know whether there really was a tension or not, and whether the needle actually reached the pleural cavity at all. Some heavy-set patients may have very thick chest walls.

Needle thoracostomies are also prone to blockage, kinking, dislodging and falling out. Thus a relieved tension may re-accumulate undetected. More importantly is the possibility of lung laceration with the needle, especially if no pneumothorax is present initially. Air embolism through such a laceration is also a real concern.