Cardiopulmonary exercise testing is a non-invasive test that allows quantification of fitness. It is an objective measure of function capacity/fitness. It has been used in patients due to undergo major surgical intervention, and has the ability to identify those patients who are at higher risk of complications and mortality. CPET has been shown to be superior to the ASA in predicting peri-operative risk. The ASA classification is similar to PS in that it is graded from 1-4, and is a bedside assessment.