[Correlation between the gradient constant of the theoretical pressure volume diagram (PVD) and the pressure volume index (PVI) in relation to brain pulse amplitude-mean pressure function].

In 54 neurosurgical patients--suffering from intracranial tumors, hydrocephalus or different kinds of brain injury--a catheter was implanted in the lateral ventricle for continuously monitoring of the intracranial pressure (ICP). The intraventricular injection of defined amounts of sodium clearance (1-2 cm3) was followed by increased values of intracranial mean pressure--(pm) and pulse-amplitude- (PA). The recorded data showed a high significant correlation after regression analysis. After determination of the pressure-volume-index (PVI) and the theoretical pressure-volume-diagram it was examined whether there is a linear correlation between the parameters of the craniospinal space (id) reserves (constant of gradient, (PVI, K of PVD)) and the gradients (CA) of the linear PA-PM-function. A significant linear relationship, however of weak degree, could be found between these two parameters. The linear PA-PM-function, therefore, can only be understood in restricted circumstances as a direct parameter of the intracranial spacial reserves. The underlying facts of these problems are dealt within this paper.