1. postoperative pulmonary complications was scored if one of the following criteria was present: (1) a patient received (non-prophylactic) antibiotics for pulmonary reasons; (2) infiltrate on chest x ray diagnosed by the radiologist; or (3) return to the intensive care unit (ICU) due to respiratory problems
2. LOS was defined as the time in hospital following surgery (in days)
3. Readmissions to the hospital within 30 days of surgery due to complications were registered
4. walking distance, measured by a 6-minute walk test (6MWT) on the day of admission and the day of discharge.