CSF outflow resistance and pressure-volume index determined by steady-state and bolus infusions

Intraventricular or lumbar CSF pressure was measured in 58 adult hydrocephalic patients. CSF outflow resistance (Rcsf) and pressure-volume index (PVI) were determined by steady-state and bolus infusion techniques, using mathematical models with and without a constant term. Comparison of the various Rcsf and PVI values indicates that the most reliable Rcsf is obtained by steady-state infusion. The best approximation of the PVI is obtained by bolus infusions, provided the pressure decay curve is excluded. Mathematically a model with a constant term is to be preferred.