Accurate measurement of core body temperature at the scene of an accident is critical for both diagnosis and treatment/triage decisions for hypothermic patients. Measurement in the lower third of the oesophagus is considered the gold standard of CT reading, but invasive and hardly applicable with a conscious patient. Tympanic membrane sensors for CT reading have been widely tested by may be unreliable in extreme environmental temperatures. Similarly, the Double Sensor device is a non-invasive device and is promising for prehospital use but has not been sufficiently verified under very cold and hot environmental conditions. Furthermore, comparisons of different non-invasive methods with oesophageal measurement in extreme conditions are lacking. The objective of these studies is to compare different techniques of core body temperature measurement with exposure to cold and hot environments.

Inclusion Criteria:

• >18 years old
• ASA class 1

Exclusion Criteria:

• <18 years old
• American society of anesthesiologists class >1
• history of ear, nose, throat surgery
• congenital malformation of head/throat/ear/nose
• absence of informed consent