Firstly, go and read Simon and Tim Harris’ great 2005 paper on the subject which we reference repeatedly in the podcast. It is available free open access here.
A pneumothorax exists when air accumulates in the potential space between the visceral and parietal pleura:
A tension pneumothorax exists when the air in the pleural cavity is under high pressure resulting in compression of the surrounding structures.
Simon mentions Rutherford’s diagram in the podcast. This is taken from a 1968 paper examining the progressive pathophysiology of a tension pneumothorax. The graph shows the changes in intrapleural pressure (on the ipsilateral and contralateral sides) in spontaneously breathing goats who had air injected into one side of their chest. We can’t find the full article free/open access anywhere I’m afraid. But this is the reference: THE PATHOPHYSIOLOGY OF PROGRESSIVE, TENSION PNEUMOTHORAX. Rutherford RB, Hurt HH, Brickman RD, Tubb JM. Journal of Trauma and Acute Care Surgery, March 1968,8(2):212-227
The imaging findings of tension pneumothorax might look like this:
More plain film images are available in this article on the Radiopaedia website.
If you want to know about ultrasound findings of pneumothorax, check out this great R.E.B.E.L.EM post.
Leigh-Smith S, Harris T. Tension pneumothorax—time for a re-think? EMJ. 2005; 22:8-16. doi.org/10.1136/emj.2003.010421
Roberts DJ, Leigh-Smith S et al. Clinical Presentation of patients with a Tension Pneumothorax – a systematic review. Annals of Surgery. 2015; 261: 1068-78. doi: 10.1097/SLA.0000000000001073