ICP measurement control: laboratory test of 7 types of intracranial pressure transducers

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Abstract
Intracranial pressure (ICP) monitoring has become an important parameter in the assessment of comatose patients, with raised intracranial pressure. The transducers in use have to fulfill the criteria of measurement accuracy, practicability and cost-effectiveness. However, these requirements are not always met in clinical practice. The need for ongoing quality control through independent laboratories remains. We have developed a laboratory set-up for the evaluation of intracranial pressure probes. Seven different types of currently used transducers have been tested for measurement accuracy. Under in vitro conditions 3 parameters were assessed: measurement accuracy, a 24 h drift and 10 day drifts. Tests for measurement accuracy were performed at increasing pressure levels of up to 80 mmHg. They were repeated 10 times per probe. This test allowed the simultaneous assessment of 5 different ICP probes. Drift was evaluated for 24 h and 10 days, at 6 pressure levels between 0 and 50 mmHg. Seven different types of ICP probes were tested (HanniSet®, Camino®, Codman®, Spiegelberg®, Medex®, Epidyn® and Gaeltec®). Measurement accuracy was best with HanniSet® probes. The maximum errors with this transducer were 3 mmHg. Camino® and Codman® showed similar results. Spiegelberg® had slightly larger deviations. With Epidyn® and Gaeltec® the highest errors were noted, up to 10 mmHg in the high pressure range. The 24 h drift was lowest with HanniSet® (0.2 mmHg) and Camino® (0.8 mmHg). The largest drifts were seen with Medex®, Spiegelberg® and Gaeltec® (1.8 mmHg). Ten day drift was lowest with HanniSet® (0.1 mmHg/day) and Codman® (0.2 mmHg/day). The highest long-term drifts were found with Epidyn® and Gaeltec® (1.5 mmHg/day). Drift did not exhibit a linear pattern. After an initial rise in drift during the first 24-72 h, it decreased slowly during the next 7 days. Most ICP probes revealed measurement inaccuracy and drift. These results emphasize the necessity for ongoing evaluations of ICP probes. Therefore, tests for quality assurance are essential to establish a consistent standard of proficiency of ICP transducers.