A computational assessment or even quantification of shear induced hemolysis in the predesign phase of artificial organs (e.g., cardiac assist devices) would largely decrease efforts and costs of design and development. In this article, a general approach of hemolysis analysis by means of computational fluid dynamics (CFD) is discussed. A validated computational model of a microaxial blood pump is used for detailed analysis of shear stress distribution. Several methods are presented that allow for a qualitative assessment of shear stress distribution and related exposure times using a Lagrangian approach and mass distribution in combination with shear stress analysis. The results show that CFD offers a convenient tool for the general assessment of shear-induced hemolysis. The determination of critical regions and an estimation of the amount of blood subject to potential damage in relation to the total mass flow are shown to be feasible. However, awareness of limitations and potential flaws in CFD based hemolysis assessments is crucial.
Hemodynamic activation of vWF and increased plasma ADAMTS-13 activity may have reduced high-molecular-weight vWF multimers and thereby impaired the vWF-platelet aggregation pathway. Additional delineation of these pathways may improve management of left ventricular assist device-associated bleeding.
A detailed knowledge of the flow field in a blood pump is indispensable in order to increase the efficiency of the pump and to reduce the shear-induced hemolysis. Thus, three different impeller designs were developed and tested by means of computational fluid dynamics (CFD) and digital particle image velocimetry (DPIV). The results show a good agreement of CFD and DPIV data. An optimization of the impeller could be achieved by following the concept of turbulent drag reduction for the axisymmetric center body.
The Hemopump is a useful left ventricular assist device. Because it is a rotary blood pump, the pump performance is not constant and is dependent on the cardiac cycle. We measured the static flow delivered by the pump at varying pressure heads (delta P) in a mock circulation. These data are compared to the pump performance in vivo. On the basis of these results, 5 sheep were instrumented for continuous Hemopump flow measurement as well as left ventricular and aortic pressure measurements. The Hemopump flow was relayed instantaneously to the pressure head. Low filling and ventricular failing (through intravenous administration of a beta-blocker) conditions were applied. The in vivo measured flows also are pressure head dependent, but the flow curve shows hysteresis resulting in a loop during each cardiac cycle. The in vivo peak flows (delta P = 0) are similar to the in vitro data. The in vivo means flows (delta = 50 mm Hg) are similar to the in vitro data for the lower pump speeds but are less than that at the higher pump speeds (3.74 +/- 0.55 L/min in vivo at Speed 7 versus 4.6 L/min in vitro). Low filling interrupts the delta P-flow loop and reduces flow. In the failing ventricle, delta P increases and flow is reduced. The cannula leaks and results in aortic insufficiency (0.36 +/- 0.05 L/min) when the pump is turned off. Several conclusions have been drawn from these tests: Cardiac activity is beneficial for the pump performance as well as when the aortic pressure curve is nonpulsatile; the longer the systolic phase, the higher the pump flow; the pump should never be turned off in clinical use, and filling is important for the pump's performance.
A lab type is best described by its value as a result of its handcrafted uniqueness in small numbers. Logically, there is not one lab type like another, and the fact that it has been realized does not mean that this special effort can be easily reproduced. Furthermore, most lab types have undergone stand alone test runs revealing fingerprints rather than universal results at a 20% effort to 80% effect ratio. A product development, on the other hand, is best described by an 80% effort to 20% effect ratio in terms of measurable results. Products are producible and cost effective goods which are well documented and have undergone numerous test runs and test procedures assuring safety and quality, a basic requirement for market approval and cost effective marking. Based on the intravascular pump technology, comprising a sensorized axial flow pump with an integrated micromotor, the iterative dependence of the product development on lab types is demonstrated showing in particular the importance of having highly developed lab types before initiating the product development. By example, we demonstrated that high product quality has a greater impact on the reduction of blood damage than numerous redesigns. Reengineering issues are addressed, which are part of the product development process. Furthermore, the previously mentioned technology serves as a platform leading directly from the perioperative biventricular system to a 7 day pump as well as a miniaturized 12 Fr version.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.