Monitoring of intracranial pressure (ICP) has been used in the management of patients with increased ICP, or in whom increased ICP was suspected. ICP depends on the relative constancy of total volume inside the skull, comprising cerebrospinal fluid (CSF), blood, and brain tissue. The changes of CSF volume affect the ventricular fluid pressure and defined it as volume pressure response (VPR). The shape or curve of the intracranial volume-pressure (V-P) relationship is well known in daily neurosurgical practice. If the P-V curve can be expressed by mathematic manner, then there should be an indicator to reflect the status of the curve. This study is conducted in order to understand the difference of each P-V curve in patients with increased intracranial pressure. The individual VPR values have been tested with three mathematical models (linear, parabolic and exponential regression equation).
