Accuracy of Zero-flux and Ingestible Thermometers

Background When a patient is anesthetised and undergoes an operation, their body temperature falls. Managing a body temperature properly by keeping it within normal limits has been shown to improve recovery from surgery. A vital part of managing temperature is being able to measure it properly. There are several ways of doing so, which consist of invasive methods such as temperature probes in the oesophagus and bladder, and non invasive methods such as infrared scanners and ear canal probes. During an operation, temperature changes as small as 0.5 °C can affect outcomes but, currently, only invasive methods are reliable enough to detect this. Oesophageal probes can't be used in patients who are not anaesthetised during their operations, and it is inappropriate to insert a urinary catheter should it not be otherwise needed. The purpose of this study is to look at two new methods of measuring a patient's temperature which would help us in these situations. The first is called zero-flux thermometry and involves placing an adhesive pad to the forehead, which gives constant measurement of a patient's core temperature. The second involves swallowing an ingestible capsule that is no bigger than a normal pill. This technique has been very useful in research tracking a patient's core temperature as they are transferred through different areas over a longer period of time. Whilst these two methods are potentially very useful, they have never been tested on hospital patients. Aims: The investigators want to determine whether readings from these thermometers are accurate enough to be used in patients before, during and after surgery. Should they prove to be sufficiently accurate it will allow us to improve patient care through both clinical practice and research. Plan: During operations, temperature is routinely measured in line with NICE guidelines with a thermometer placed in the nose or oesophagous. The investigators will not be changing routine practice in any way, bu