On this particular patient, considering how far they opened the chest and even pulled out a lung almost all the way, it was most likely for learning purposes. But, most of the time if the chest has to be cracked, the patient is pretty much dead anyway. I have never seen one survive. It is basically a last resort type of thing if the attending thinks there is any chance of survival. GSW(gun shot wounds) to the chest are a common one. If the bullet is lodged in the heart or surround area, they might crack open to try and remove it and then start pumping to try and save them. It is quite a site when the crack happens, looks like someone dumps a 5 gallon bucket of red paint on the floor. True story!