Cerebral hemodynamics during arterial and CO2 pressure changes: in vivo prediction by a mathematical model

The aim of this work was to analyze changes in cerebral hemodynamics and in tracranial pressure (ICP) evoked by mean systemic arterial pressure (SAP) a nd arterial CO2 pressure (Pa-CO2) challenges in patients with acute brain d amage. The study was performed by means of a new simple mathematical model of intracranial hemodynamics, particularly aimed at routine clinical invest igation. The model was validated by comparing its results with data from tr anscranial Doppler velocity in the middle cerebral artery (V-MCA) and ICP m easured in 44 tracings on 13 different patients during mean SAP and Pa-CO2 challenges. The validation consisted of individual identification of 6 para meters in all 44 tracings by means of a best fitting algorithm. The paramet ers chosen for the identification summarize the main aspects of intracrania l dynamics, i.e., cerebrospinal fluid circulation, intracranial elastance, and cerebrovascular control. The results suggest that the model is able to reproduce the measured time patterns of V-MCA and ICP in all 44 tracings by using values for the parameters that lie within the ranges reported in the pathophysiological literature. The meaning of parameter estimates is discu ssed, and comments on the main virtues and limitations of the present appro ach are offered.