Estimation of the main factors affecting ICP dynamics by mathematical analysis of PVI tests.

A simplified model of intracranial dynamics is used to reproduce the intracranial pressure (ICP) time pattern in 20 patients with severe brain damage during PVI tests. A comparison of model responses and clinical tracings was achieved by minimizing a least square criterion function and adjusting just 5 parameters. These are: the CSF outflow resistance, the intracranial elastance coefficient, the autoregulation gain and time constant, and the basal values of arteriolar compliance. Based on the value of the autoregulation gain, the patients were classified into two groups: those with damaged autoregulation (8 out of 12) and those with preserved autoregulation (12 out of 20). Finally, analysis of the correlation between parameter estimates provided suggestions on the combination of a parameter changes which may have the greater impact on ICP in the individual cases. Once these parameters have been identified, they may become possible targets for therapeutic interventions.