Thoracotomy is an incision into the chest. It is performed by a surgeon, and, rarely, by emergency physicians and paramedics, to gain access to the thoracic organs, most commonly the heart, the lungs, the esophagus or thoracic aorta, or for access to the anterior spine such as is necessary for access to tumors in the spine.

Thoracotomy is a major surgical maneuver—the first step in many thoracic surgeries including lobectomy or pneumonectomy for lung cancer—and as such requires general anesthesia with endotracheal tube insertion and mechanical ventilation.

Thoracotomies are thought to be one of the hardest surgical incisions to deal with post-op, because they are exquisitely painful and the pain can prevent the patient from breathing effectively, leading to atelectasis or pneumonia.

From http://en.wikipedia.org/wiki/Thoracotomy