Tension pneumothorax (summary)

Last revised by Andrew Murphy on 3 Jan 2020
This is a basic article for medical students and other non-radiologists

Tension pneumothoraces are pneumothoraces under pressure. If the pressure gets high enough, the pneumothorax can compress the heart and great vessels, and even cause cardiac arrest.

Presentation is usually with respiratory compromise and chest pain, although if the pneumothorax is under enough pressure, it may impact venous return with resultant distended neck veins and eventual circulatory collapse and cardiac arrest.

A tension pneumothorax occurs when there is progressive accumulation of gas within the pleural cavity. This is usually caused by a ball-valve effect with progressive increases in intrapleural air during each expiration. The thoracic cavity has a relatively fixed volume and therefore, as the volume of gas increases, the pressure rises.

Pneumothoraces are seen as areas of increased lucency. Tension pneumothoraces tend to be large and result in relative lucency of the entire hemithorax. Associated mass effect on ribs, diaphragm and mediastinum results in increased rib spacing, depression of the diaphragm and displacement of the mediastinum to the contralateral side of the chest.

A tension pneumothorax must be diagnosed early and treated with urgency. Initial decompression with a needle or cannula in the 2nd intercostal space anteriorly will reduce the pressure 1.

A chest drain should be inserted to ensure that tension does not recur. Assessment should include attempts to determine the underlying cause. If treated early with appropriate drainage, prognosis is excellent.

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Cases and figures

  • Figure 1: mediastinal shift
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  • Figure 2: hemidiaphragm depression
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  • Figure 3: hemithorax hyperexpansion
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  • Case 1: right sided tension pneumothorax
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  • Case 2: right sided tension pneumothorax
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  • Case 3: tension pneumothorax on CT
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  • Case 4: tension pneumothorax post biopsy
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  • Case 5: with no mediastinal shift
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