Laboratory testing of the Spiegelberg brain pressure monitor: a technical report Commentary

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/°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.