Background: In clinical practice, fiberberoptic and piezo-electric ICP probes are often used for measuring intracranial pressure (ICP). A number of similar technologies, although performing well in bench test studies, have been shown to exhibit unacceptable zero drift, fragility or both during trials conducted under clinical conditions. Recently, a new technology has become available, the Neurovent-P (Raumedic AG + CO, Raumedic, Germany). As a pre-requisite for a clinical trial, we have conducted and report on bench test studies to confirm the manufacturer's long term zero-drift performance for this technology.
Method: In a test rig static tests (recording of 20 mmHg pressure) and dynamic tests, ranging from 5 to 50 mmHg have been performed.
Findings: 10 ICP probes have been tested for a total of 60 days. All the catheters, after the connection with the ICU monitor displayed a static pressure of 0 +/- 1 mmHg and did not required pre-insertion alteration. At five days, mean zero drift was 0.6 +/- 0.9 mmHg. Overall, zero drift ranged from 0 to 2 mmHg. At a fixed static pressure of 20 mmHg, the mean recorded value was 20.6 +/- 0.8 mmHg, ranging from 19 to 23 mmHg. A regression analysis of the relationship between the applied pressure and the recorded pressure during the dynamic tests of the 10 catheters yielded a correlation coefficient R2 of 0.997. Applying the Altman and Bland method to assess the bias and confidence limits for the Raumedic catheter responses during the dynamic tests against the applied gold-standard hydrostatic column pressures, the average bias of -0.66 +/- 0.85 mmHg, with 95% CLs of -2 mmHg and 1 mmHg.
Conclusions: Mean zero drift, after five days, was very small and long-term continuous recording of a stable pressure was very precise. The response at dynamic tests, i.e. the changes of pressure in a wide range, was excellent. The average bias of the Raumedic catheter compared with the hydrostatic column is very small. After this bench test, the next and most critical step will be to conduct a trial of this promising technology under more demanding clinical environment.