Computer analysis of the main parameters extrapolated from the human intracranial basal artery blood flow

In the present work an original mathematical model of human intracranial dynamics is used to analyze the clinical significance of several parameters (systolic, diastolic, and mean blood flow, Gosling pulsatility index, and Pourcelot index) extrapolated from the intracranial basal artery blood flow waveform. In the model all the main phenomena characterizing intracranial dynamics (craniospinal pressure-volume relationship, arterial and venous intracranial compliance, cerebrospinal fluid production and absorption rates, cerebral autoregulation, terminal vein collapse) have been included according to anatomical and physiological data. From an analysis of the model simulation curves we can conclude that, if cerebral autoregulation is working well, only minor changes in blood flow patterns may be expected during moderate intracranial hypertension. However, when intracranial pressure is in the range of 40-60 mm Hg, the pulsatility and Pourcelot indexes exhibit a fairly linear dependence on ICP. However, this dependence may be less evident than expected because of changes in the ICP pulse amplitude. Finally, when the ICP exceeds about 70 mm Hg, the pulsatility index exhibits a disproportionate increase. This condition is associated with an evident increase in blood flow pulse amplitude. Moreover, with the present computer model not only the effect of intracranial pressure changes, but also that of several other biophysical factors (such as arterial compliance, craniospinal pressure-volume relationship, regulatory actions) on the intracranial artery blood flow shape can be analyzed and related to signals obtained using the Doppler transcranial technique.