The purpose of using Computational Fluid Dynamics (CFD) in designing perfusion equipment is to maximize blood handling within the context of achieving design goals for specific devices. In the current case, the goals were: to reduce priming volume and blood damage due to fluid shear in the Medtronic Maxima Forte® oxygenator; to reduce blood damage due to shear in the new Medtronic Bio-Medicus Bio-Pump®; and to maintain low shear and promote good mixing in the Maxima Forte Hardshell Reservoir.
CFD allows prediction of, among other phenomena, regions of high shear and regions of stagnation that are detrimental within blood handling devices. These predictions allow a directed approach to design of blood handling devices that is more effective than a prototype-and-test approach in establishing efficient yet safe designs.
In the case of the Maxima Forte oxygenator, CFD indicated that a very low volume inlet manifold was not only achievable, but also necessary to eliminate large areas of recirculation.
The design of the transition manifold between the heat exchanger and the gas exchange bundle resulted from a sequence of CFD models: the final design, which is incorporated in the Maxima Forte oxygenator, being arrived at by balancing priming volume and fluid shear.
In the design of the Maxima Forte Hardshell Reservoir, CFD was used to verify effective mixing between the cardiotomy and venous blood, and to choose between design alternatives while maintaining low fluid shear.
In optimizing the new Medtronic Bio-Medicus Bio-Pump, CFD was used to identify the pump’s cutwater as a location of high fluid shear, and to decide between five design alternatives to minimize shear on the cutwater. In-vitro feasibility testing indicates that the cumulative effect of design changes identified by using CFD results in reduction of hemolysis of 22% (p = 0.000014) over the BP-80 Bio-Pump.
CFD is a powerful predictive design tools that, when used suitably with experiment, can be used to improve the design of all perfusion equipment directly involving flowing blood.