Mass transfer in vascular access ports

Numerical simulations have been performed to evaluate the fluid flow and mass transfer processes that occur in a human-body vascular-access port. Such ports are used to facilitate the frequent introduction of cleansed blood and other drugs into the body from external sources. Each of the infusion ports studied here consists of a reservoir and an attached tube-like catheter which delivers the infused medium to its point of use. All told, three unique infusion ports were investigated. Each had a particular geometry characterized by the shape of the reservoir and the mode of attachment of the catheter to the reservoir. The numerical simulations were three-dimensional and unsteady. Both Newtonian and non-Newtonian constitutive equations were employed for the fluid flow solutions and for the subsequent mass transfer solutions. The initiation of fluid motion was the injection of a controlled volume of fluid into the reservoir. In some cases, the injected fluid was the same as that in the reservoir, and in others it was different. For all the investigated infusion systems, no hemolysis (red blood cell destruction) was in evidence when blood was passed through the catheter. Potential hemolysis was averted in two of the systems due to the very low fluid velocities. As witnessed by the mass transfer results, the use of the reservoir as a chamber to mix a secondary liquid with blood is a viable strategy.