This was asked about in Question 15 from the first paper of 2000.
In brief:
Isolate the affected lung.
If the lung is not isolated:
If the lung is isolated:
Attempt temporary haemostasis.
Establish definitive haemostasis
Lastly;
Family conference and full disclosure.
The historical mortality rate from these is about 70%.
Kearney, Thomas J., and M. Michael Shabot. "Pulmonary artery rupture associated with the Swan-Ganz catheter." CHEST Journal 108.5 (1995): 1349-1352.
Bossert, Torsten, et al. "Swan‐Ganz Catheter‐Induced Severe Complications in Cardiac Surgery: Right Ventricular Perforation, Knotting, and Rupture of a Pulmonary Artery." Journal of cardiac surgery 21.3 (2006): 292-295.
Bussières, Jean S. "Iatrogenic pulmonary artery rupture." Current Opinion in Anesthesiology 20.1 (2007): 48-52.