Healthcare workers measure heart rate, blood pressure, temperature, oxygen levels and breathing rate to monitor how unwell a patient is. All these apart from breathing rate are now normally measured by machines. But there still isn't a machine that does this well enough for breathing rate to be used in most places. The machines that do exist are either uncomfortable or don't work well on patients who are moving. Instead, a healthcare worker will count the number of breaths a patient takes. This needs staff time and isn't very accurate.

It is known that changes in breathing rate can happen any time. But healthcare systems normally only measure it every few hours because it takes time. Breathing rate could be monitored all the time, we might pick up people getting sick earlier and be able to treat them more quickly, which could save lives.

A team at the University of Southampton has made a small device, called a PneumoRator, that gets stuck to onto a person's chest. Once stuck there it can measure their breathing rate and store or send that information wirelessly. The device has been tested on healthy volunteers but has never been tested on patients in hospital.

In this study the team will put the device on patients having major operations. The investigators will record information already collected about patients during normal care. This includes their breathing rate using the best measurement we have, where a patient's breathing is measured by a gas they breathe out. The gas is carbon dioxide, and the measurement is called capnography. This way of measuring is only used in operating theatres and intensive care units but is a good way to check if the PneumoRator is accurate.

The investigators want to attach the PneumoRator to patient's chests before they go to sleep for their operation and leave it there for the first few days after their operation. This will let them see how the PneumoRator compares to capnography and manual breath counting. It will also let them see how the device works at different times in the patient's journey. The investigators will look at the time when patients are asleep, when breathing is controlled by a machine. Then when patients wake up investigators can measure with both capnography and the PneumoRator. Finally, when patients go to the high dependency ward, investigators will compare it against manual counting. The study team will also ask patients how they found wearing the device and any problems they found.

With this information the investigators hope to show the PenumoRator is accurate at measuring breathing rate and comfortable for patients. This will help them get the device approved for use in hospitals and other places where breathing rate needs to be measured accurately.

Inclusion Criteria:

1. Have undergone or are referred for CPET
2. are scheduled for elective surgery and expected to have >24 hours postoperative hospital stay
3. Will be admitted to the Surgical High Dependancy Unit (SHDU) as part of their planned care
4. will receive invasive arterial pressure monitoring as part of routine care
5. are aged 18 or over
6. have the capacity to give consent to participate

Exclusion Criteria:

1. do not proceed to surgery following CPET referral
2. are aged less than 18 years
3. do not have capacity to consent
4. decline to consent
5. have sensitivity or allergy to medical adhesives
6. patients with fragile, erythematous, or broken skin at the site of PnemoRator attachment or any other condition which, in the view of the clinical research team, may mean that the use of the PnemoRator device and adhesive is likely to cause patient harm.
7. patients with implantable electronic medical devices (e.g. pacemakers, nerve stimulators)

The study comprises patients undergoing intermediate-high risk major surgery at University Hospital Southampton who are planned for admission to the Surgical High dependency unit (SHDU)