The Problem of Long-Term ICP Drift Assessment: Improvement by Use of the ICP Drift Index

Summary

 Background. Intracranial pressure (ICP) monitoring is dependent on the precise measurement of absolute pressures and low drifts of the different transducers in use. Our investigations have shown that probes sometimes appear to reveal positive and negative drifts consecutively. There is no regard for any of these important pressure changes by the mere result of the traditional drift. Therefore, we have developed a more precise way of assessing the behavior of the ICP drift.

 Method. A special laboratory set up for the simulation of constant pressures, at definite temperatures, was designed. We examined the Camino®-110-4B, Gaeltec® ICT/B, HanniSet® and Spiegelberg® transducers.

 Drift index is a new term that has been developed by our group to provide a better description of the actual pressure changes over long-term measurement. The drift index consists of three parameters: the percentage of measurements which show a pressure change during the 10 days of measurement; the maximum absolute pressure deviation that occurred during a ten day measurement; and the mean absolute pressure deviation during a 10 day measurement.

 Findings. The median proportion of pressure changes during ten days were: Camino: 1.59%; Gaeltec: 0.71%; HanniSet: 0.08%; Spiegelberg: 4.00%; The median maximum absolute pressure changes were 6; 9.5; 1; and 11 mmHg for the four types and the median mean absolute pressure changes were 2.9; 5.1; 0; and 2.4 mmHg, respectively. The median 10 day classical drift in each type of transducer was 4; 9; 0; and 2 mmHg, respectively.

 Interpretation. We recommend the use of the drift index to be used by manufacturers. This is an additional vital parameter in order to improve ICP measurement accuracy and the proficiency of ICP monitoring.