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Critical Care

, 13:R106

First Online: 02 July 2009Received: 09 March 2009Revised: 28 April 2009Accepted: 02 July 2009


IntroductionThe influence of brain temperature on clinical outcome after severe brain trauma is currently poorly understood. When brain temperature is measured directly, different values between the inside and outside of the head can occur. It is not yet clear if these differences are -real- or due to measurement error.

MethodsThe aim of this study was to assess the performance and measurement uncertainty of body and brain temperature sensors currently in use in neurocritical care. Two organic fixed-point, ultra stable temperature sources were used as the temperature references. Two different types of brain sensor brain type 1 and brain type 2 and one body type sensor were tested under rigorous laboratory conditions and at the bedside. Measurement uncertainty was calculated using internationally recognised methods.

ResultsAverage differences between the 26°C reference temperature source and the clinical temperature sensors were +0.11°C brain type 1, +0.24°C brain type 2 and -0.15°C body type, respectively. For the 36°C temperature reference source, average differences between the reference source and clinical thermometers were -0.02°C, +0.09°C and -0.03°C for brain type 1, brain type 2 and body type sensor, respectively. Repeat calibrations the following day confirmed that these results were within the calculated uncertainties. The results of the immersion tests revealed that the reading of the body type sensor was sensitive to position, with differences in temperature of -0.5°C to -1.4°C observed on withdrawing the thermometer from the base of the isothermal environment by 4 cm and 8 cm, respectively. Taking into account all the factors tested during the calibration experiments, the measurement uncertainty of the clinical sensors against the nominal 26°C and 36°C temperature reference sources for the brain type 1, brain type 2 and body type sensors were ± 0.18°C, ± 0.10°C and ± 0.12°C respectively.

ConclusionsThe results show that brain temperature sensors are fundamentally accurate and the measurements are precise to within 0.1 to 0.2°C. Subtle dissociation between brain and body temperature in excess of 0.1 to 0.2°C is likely to be real. Body temperature sensors need to be secured in position to ensure that measurements are reliable.

AbbreviationsDPEdiphenyl ether

ECethylene carbonate

ICPintracranial pressure

NCCneurocritical care.

Electronic supplementary materialThe online version of this article doi:10.1186-cc7943 contains supplementary material, which is available to authorized users.

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Autor: Charmaine Childs - Graham Machin


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