LABORATORY TESTING OF THE SPIEGELBERG BRAIN PRESSURE MONITOR - A TECHNICAL REPORT

Objectives-The Spiegelberg brain pressure monitor is a low cost intrac ranial pressure monitoring system that has been used clinically for so me time, mainly in Germany. To provide a rigorous bench comparison of the Spiegelberg monitor with the Camino pressure monitor an evaluation programme has been carried out in the UK Shunt Evaluation Laboratory. Design-Drift over 72 hours and with temperature, a frequency response , and the accuracy of measurement of both static and pulsatile pressur es have been tested simultanously in Camino and Spiegelberg transducer s using a computerised rig. Results-Long term zero drift was less than 0.7 mm Hg in both transducers. The Spiegelberg monitor showed no temp erature drift whereas the Camino monitor had a drift of around 0.3 mm Hg/degrees C. The Spiegelberg monitor underread mean pressures <40 rum Hg by <1 mm Hg, but the error increased to 4.7 mm Hg at 100 mm Hg. Th e frequency bandwidth of the Spiegelberg monitor was 4 Hz at a low pre ssure. Underreading of the amplitude increased with the mean pressure, with a delay of about 0.1 s in the detection of the peaks of pulse wa veform. Conclusion-The Spiegelberg transducer had excellent accuracy f or static intracranial pressure measurement, but complex waveform anal ysis may be biased by its limited dynamic response.