Abstract
A ventriculoperitoneal shunt is a medical device used in the treatment of a medical
condition called hydrocephalus by draining cerebrospinal fluid from the ventricles to
the peritoneal cavity. A common cause of shunt failure, other than mechanical failure,
is infection. This study looks at the modelling of fluid and particulate flow through a
ventriculoperitoneal shunt in an environment with changing temperature. The main
aim of this study is to observe how a ventriculoperitoneal shunt would perform in a
situation that would create shunt occlusion that would possibly be accelerated an
infection. An experiment was run, where a mixture of water and gelatine powder was
pushed through a Medtronic CSF Flow Control Valve using a syringe pump at set
concentrations and volume flow rate at the inlet, to simulate the flow of CSF with blood
cells and protein in a real-life situation. The temperature of the water bath, in which
the shunt valve was immersed, varied between 37℃ and 41℃, increasing by 1℃ per
test run. The volume of the mixture at the outlet was recorded and the outlet volume
flow rate was calculated to determine if there is shunt occlusion. CFD models were
generated with the same inlet flow parameters as the experiment test bench. The
particulates used in these models were two types of white blood cells and albumin, a
type of protein. Validation of the model was done, and the individual models were run
to obtain a volume flow rate of the mixture at the outlet of the VP shunt which would
indicate if there was shunt occlusion. The most important result that was obtained from
both the experiment and the CFD model was that there is no definite relationship
between increasing temperature and particulate concentration, and a blockage within
the shunt valve. The volume flow rates of the water/gelatine mixture in the experiment
and the CSF mixture in the CFD model do not decrease in a manner that would
indicate shunt occlusion. The results obtained are valid in that the assumptions are
made that infection occurs because of an increase in the temperature of the CSF and
the surfaces of the shunt system, and an increase in the number of particulates
contained in the CSF due to an increase in the number of leukocytes needed to fight
an infection. Further studies that could be done include focusing on the biological
implications of an infection beyond heat transfer and particulate mechanics. Bacterial
growth along the walls of the catheters and the shunt valve could be modelled to gain
a more comprehensive understanding of the effects of infection on the potential of a blockage within the VP shunt, as well as the non-Newtonian behaviour of the fluid because of the presence of albumin in the CSF, which is a soluble particulate.