Volume/pressure relationship of the cerebrospinal space in humans.

Using constant flow rate infusions and compensating for the fluid formed and eliminated, the net volume/pressure (V/p) relationship of the cerebrospinal fluid (CSF) space in humans was investigated in more than 200 patients. Of these, 16 patients constitute a normal reference material. Reference values for the variables characterizing the V/p relationship are reported. The V/p relationship was found to be nonexponential, which is not consistent with the pressure-volume index theory. The reactivity of the vascular bed during induced CSF volume changes had to be taken into account when analyzing the results. There were reasons to believe that the major volume changes during the recording of the V/p relationship took place in the spinal part of the CSF space and that the pressure of minimal elastance corresponded to the spinal epidural venous pressure.