The investigators would like to evaluate the use of cardiopulmonary exercise tests (CPX) in guiding the care pathway of patients undergoing colorectal operations. In the intervention group care will be guided by CPX results and in the control group care will be guided by the doctors assessment. The investigators would like to assess the impact of this on patient outcome, patient satisfaction and resource usage.

Each year 20000 UK patients die within 30 days of surgery. It seems that in the UK a patient's chances of becoming seriously unwell or dying following surgery is higher than in comparable countries. Fewer beds in the UK are given over to Intensive Care than in these other countries. Closer attention to the care given after operations, which can be achieved on intensive care units (ICU), almost certainly reduces the chances of serious illness following major surgery. An increase in the number of intensive care unit beds in the UK is extremely unlikely. Better use of the available intensive care beds could be achieved by allocating them where they are believed to improve outcome (following surgery) and by allocating them to patients most likely to benefit.

Tests used to assess risk of surgery to patients are largely ineffective. Cardiopulmonary exercise tests (CPX) seem to be effective at identifying patients at risk of death or serious illness post surgery. This information has been used in studies to select patients for ICU beds and reduce deaths. The studies so far have limitations in their design and scope which means we can't be certain this approach works in the UK.

We suggest a study to answer this question more conclusively and more specifically in UK patients. We will randomly divide patients between two groups. In the 1st group choice of postoperative care environment is based on best current practice and in the other group we will make these decisions (critical care or ward) based on the results of the CPX.

We hope that the benefits will include less patients becoming seriously ill or dying and shorter stays in hospital after surgery following major operations. We also hope the information will help patients understand the risks of their operation better and therefore make better informed decisions. This may also reduce the overall cost of surgery for hospitals.

Inclusion Criteria:

1. Adults ≥ 18 years age
2. Males
3. Females
4. Listed for elective(non-emergency) colorectal surgery

Exclusion Criteria:

1. Age < 18 years age

2. Patient unwilling/unable to consent

3. Adults with learning disabilities or dementia

4. Prisoners

5. Any contraindication to cardiopulmonary exercise testing (as outlined by *American Association of Anaesthesia:

   • Acute MI (3-5 days)
   • Unstable angina
   • Uncontrolled arrhythmias
   • Syncope
   • Acute endocarditis
   • Acute myocarditis
   • Acute pericarditis
   • Symptomatic severe aortic stenosis
   • Uncontrolled heart failure
   • Acute pulmonary embolism or infarction
   • Thrombosis of lower extremities
   • Dissecting aneurysm
   • Uncontrolled asthma
   • Pulmonary oedema
   • Room air desaturation at rest <85%
   • Respiratory failure
   • Acute non-cardiopulmonary disorder that may affect exercise performance or be aggravated by exercise Mental impairment leading to inability to co-operate

6. Patients already enrolled in an interventional study

7. Previous CPX test result recorded in the medical notes