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Tension pneumothorax

Dr Ian Bickle and Dr Frank Gaillard et al.

A tension pneumothorax occurs when intrapleural air accumulates progressively in such a way as to exert positive pressure on mediastinal and intrathoracic structures. It is a life threatening occurrence requiring rapid recognition and treatment is cardiorespiratory arrest is to be avoided. 

For a general discussion, refer to the pneumothorax article. 

Clinical Presentation

Presentation is variable and may initially have no symptoms. With time severe dyspnea, tachycardia and hypotension occur. Distended neck veins and tracheal deviation are also often present. Eventually impaired venous return results in cardiac arrest and death. This can occur within minutes. 

Pathophysiology

A tension pneumothorax occurs due to the progressive accumulation of intrapleural gas in thoracic cavity caused by a valve effect during inspiration/ expiration. In this situation, the ipsilateral lung will, if normal, collapse completely (although a less than normally compliant lung may remain partially inflated). In either case as the collection grows further it exerts positive mass effect on the mediastinum (compressing veins, and the heart) and the opposite lung. 

Radiographic features

A pneumothorax will have the same features as a run-of-the-mill pneumothorax with a number of addition features, helpful in identifying tension. These include:

  • over expanded hemithorax
  • shift of the mediastinum to the contralateral side
  • depression of the hemidiaphragm

Treatment and prognosis

Treatment of a tension pneumothorax is one of the classic medical emergencies where a life can be saved or loss on the basis of recognition and rapid decompression. Numerous techniques exist, and the literature is replete with opinions, but in the first instance relieving the tension, even if not draining the pneumothorax is life saving. A needle thoracostomy (e.g. 14G intravenous canula) can be inserted, typically in the 2nd intercostal space in the midclavicular line, to gain valuable time, before a larger underwater drain can be inserted 1. 

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