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

Intracranial pressure (ICP) monitoring has become an important parameter in the assessment of comatose patients, with raised intracranial pressure. Th e 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 throu gh independent laboratories remains. We have developed a laboratory set-up for the evaluation of intracranial pressure probes. Seven different types o f currently used transducers have been tested for measurement accuracy. Und er in vitro conditions 3 parameters were assessed: measurement accuracy, a 24 h drift and 10 day drifts. Tests for measurement accuracy were peformed at increasing pressure levels of up to 80 mm Hg. They were repeated 10 time s per probe. This test allowed the simultaneous assessment of 5 different I CP probes. Drift was evaluated for 24 h and 10 days, at 6 pressure levels b etween 0 and 50 mmHg. Seven different types of ICP probes were tested (Hann iSet((R)), Camino((R)), Codman((R)), Spiegelberg((R)), Medex((R)), Epidyn(( R)) and Gaeltec((R))). Measurement accuracy was best with HanniSet((R)) pro bes. The maximum errors with this transducer were 3 mmHg. Camino((R)) and C odman((R)) showed similar results. Spiegelberg((R)) had slightly larger dev iations. With Epidyn((R)) and Gaeltec((R)) the highest errors were noted, u p to 10 mmHg in the high pressure range. The 24 h drift was lowest with Han niSet((R)) (0.2 mmHg) and Camino((R)) (0.8 mmHg). The largest drifts were s een with Medex((R)), Spiegelberg((R)) and Gaeltec((R)) (1.8 mmHg). Ten day drift was lowest with HanniSet((R)) (0.1 mmHg/day) and Codman((R)) (0.2 mmH g/day). The highest long-term drifts were found with Epidyn((R)) and Gaelte c((R)) (1.5 mmHg/day). Drift did not exhibit a linear pattern. After an ini tial 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. Th ese results emphasize the necessity for ongoing evaluations of ICP probes. Therefore, tests for quality assurance are essential to establish a consist ent standard of proficiency of ICP transducers.