ICP measurement accuracy: the effect of temperature drift. Design of a laboratory test for assessment of ICP transducers

Intracranial pressure (ICP) monitoring has become the mainstay of multimoda l neuromonitoring of comatous patients after head injury. In the presence o f rising ICP and faced with pressures, difficult to control, aggressive mea sures, such as hypothermia may be used. The ICP reading should not be influ enced by temperature changes. A laboratory test was designed to simulate te mperature variations between 20 degrees C and 45 degrees C at different pre ssure levels under physiological conditions. Five types of transducers were examined: Epidyn(R) Braun Melsungen, ICT/B-Titan Gaeltec(R), Camino(R) -OL M-110-4B, Codman(R) MicroSensor ICP-Transducer, Neurovent(R) ICP transducer Rehau Ag+Co. Tests were performed at 6 different pressure levels between 0 mmHg and 50mmHg. The results show very low drifts of less than 0.15 mmHg d egrees C-1 for Codman, Epidyn and Neurovent. Gaeltec and Camino exhibited h igher drifts of 0.18 mmHg and 0.2 mmHg degrees C-1 respectively. Within the temperature range from 35 degrees C to 42 degrees C all probes tested show insignificant temperature drift. Whether these results also apply to other types of transducers needs further evaluation. Problems and requirements r elated to the design of a laboratory test for the in vitro assessment of IC P transducers are discussed in detail.