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Laboratory testing of the Spiegelberg brain pressure monitor: a technical report
M Czosnyka1, Z Czosnyka, J D Pickard
1The UK Shunt Evaluation Laboratory, Addenbrooke's Hospital, Cambridge, UK. MC141@MEDSCHL.CAM.AC.UK
Objectives:
The Spiegelberg brain pressure monitor is a low cost intracranial pressure monitoring system that has been used clinically for some 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 pressures have been tested simultanously in Camino and Spiegelberg transducers using a computerised rig.
Results:
Long term zero drift was less than 0.7 mm Hg in both transducers. The Spiegelberg monitor showed no temperature drift whereas the Camino monitor had a drift of around 0.3 mm Hg/degrees C. The Spiegelberg monitor underread mean pressures <40 mm Hg by <1 mm Hg, but the error increased to 4.7 mm Hg at 100 mm Hg. The frequency bandwidth of the Spiegelberg monitor was 4 Hz at a low pressure. 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 waveform.
Conclusion:
The Spiegelberg transducer had excellent accuracy for static intracranial pressure measurement, but complex waveform analysis may be biased by its limited dynamic response.