A number of baseline and peri-operative variables that were used to describe the study
population and which may influence postoperative outcome were extracted from the patients’
medical records: sex, age, smoking (yes/no), presence of comorbidities (heart failure/chronic
obstructive pulmonary disease/diabetes mellitus), body mass index (BMI in kg/m2),
presurgical therapy (no therapy/chemotherapy/radiation therapy/chemoradiation therapy), type
of surgery (colorectal/ liver/ oesophageal/stomach/‘other’), laparoscopic surgery (yes/no) and
surgery >150 minutes (yes/no). Additionally, baseline 6MWT was considered as a covariable.