The monitoring of relative changes in compartmental compliances of brain.

The study aimed to develop a computational method for assessing relative changes in compartmental compliances within the brain: the arterial bed and the cerebrospinal space. The method utilizes the relationship between pulsatile components in the arterial blood volume, arterial blood pressure (ABP) and intracranial pressure (ICP). It was verified by using clinical recordings of intracranial pressure plateau waves, when massive vasodilatation accompanying plateau waves produces changes in brain compliances of the arterial bed (C(a)) and compliance of the cerebrospinal space (C(i)). Ten patients admitted after head injury with a median Glasgow Coma Score of 6 were studied retrospectively. ABP was directly monitored from the radial artery. Changes in the cerebral arterial blood volume were assessed using Transcranial Doppler (TCD) ultrasonography by digital integration of inflow blood velocity. During plateau waves, ICP increased (P = 0.001), CPP decreased (P = 0.001), ABP remained constant (P = 0.532), blood flow velocity decreased (P = 0.001). Calculated compliance of the arterial bed C(a) increased significantly (P = 0.001); compliance of the CSF space C(i) decreased (P = 0.001). We concluded that the method allows for continuous monitoring of relative changes in brain compartmental compliances. Plateau waves affect the balance between vascular and CSF compartments, which is reflected by the inverse change of compliance of the cerebral arterial bed and global compliance of the CSF space.