A new method and software for quantitative analysis of continuous intracranial pressure recordings.

Objective: A computer software utilising a new method for quantitative analysis of intracranial pressure (ICP), was developed to provide a more accurate analysis of continuously recorded ICP. Intracranial pressure curves were analysed by the software to explore the relationship between mean ICP and the presence of ICP elevations.

Methods: The Sensometrics Pressure Analyser (version 1.2) software provides a quantitative analysis of the ICP curve, presenting the ICP recordings as a matrix of numbers of ICP elevations of different levels (e.g. 20 or 30 or 40 mmHg) and durations (e.g. 0.5, 5 or 10 minutes). The number of ICP elevations may be standardised by calculating the number of elevations during for instance a 10 hour period. The computer software was used to retrospectively analyse the ICP curves in our first consecutive 127 patients undergoing continuous 24 hours ICP monitoring during the two-year period from February 1997 to December 1998. The indications for ICP monitoring were suspected hydrocephalus, craniosynostosis or shunt failure.

Results: Analysis of the ICP curves revealed a rather weak relationship between mean ICP and the number of apparently abnormal ICP elevations (that is elevations of 20 mmHg or above). Abnormal ICP elevations were present in a relatively high proportion of cases with a normal mean ICP below 10 mmHg, or a borderline mean ICP between 10 and 15 mmHg. In addition, the ICP data of two cases are presented suggesting that mean ICP may be an inaccurate measure of ICP.

Conclusions: The results of analysing ICP curves by means of this method and software reveal that calculation of ICP elevations of different levels and durations may represent a more accurate description of the ICP curve than calculation of mean ICP. The method may enhance the clinical application of ICP monitoring.