In comes someone with a penetrating injury to the chest, CPR in progress. This is always a bad sign.
Into the trauma bay, no pulse, no pressure, no tracing. A quick ED thoracotomy later and I find a pericardium that hissed at me when I opened it. Along with a large pericardial clot was a rush of air. I reached in to start open cardiac massage and found a huge hole in the atrium. With every breath came a significant amount of the air through the open atrium.
There’s a reason that ED thoracotomies have a historically high mortality.