Fluid Mechanics of the Stagnation Point Flow Chamber and Its Platelet Deposition

Abstract

The interaction of flow and thrombus generation often is a crucial question for the engineer working in the field of artificial organs. However, this interaction is only incompletely known, and quantitative data under well-defined experimental conditions are especially rare. These can be attained with the stagnation point flow chamber. This flow model applies platelet-rich plasma (PRP) as fluid. Its flow conditions are assessed with the help of computational fluid mechanics. In addition, the concept of the boundary layer is introduced, which permits assessment of the platelet flow along the wall. The results of the experiment indicate that platelets are deposited at a defined shear rate.

A Model Incorporating Some of the Mechanical and Biochemical Factors Underlying Clot Formation and Dissolution in Flowing Blood

“…The details surrounding the process of platelet activation, adhesion and aggregation can be found in Lasslo (1984), Yamazaki and Mustard (1987) and Anthony Ware and Coller (1995). Macroscopic studies of platelet adhesion, deposition and thrombus formation in annular flow chambers Baumgartner (1973) (or in the stagnation point flow chamber (Affeld et al (1995)) have shown that the rate and extent of platelet adhesion, platelet deposition and platelet thrombus (or mural thrombus) formation are affected by the flow conditions (shear rates) (Weiss et al, 1978;Tschopp et al, 1979;Turitto and Baumgartner, 1979;Turitto et al, 1980; see also Alevriadou et al (1993) for the effect of flow conditions on vWF mediated platelet aggregation), the presence of citrate , and surface properties (Baumgartner et al, 1976;Baumgartner, 1977; see also Hubbell and McIntire, 1986). Platelet activation itself (Kroll et al, 1996;Christodoulides et al, 1999), and sometimes lysis, is known to occur in response to prolonged exposure to high shear stresses (Wurzinger et al, 1985).…”

Computational Fluid Dynamic Analysis of the Flow around the Pivot Bearing of the Centrifugal Ventricular Assist Device (Effects of Design Variations of the Washout Hole, the Pivot and the Back Gap)

“…A slightly stagnant region occurred in close proximity to the pivot friction region when the pivot friction area was 0 or 1.6 mm 2 . However, this stagnant region disappeared when the pivot friction area was 3.6 or 8 mm 2 . On the other hand, the region except for that in close proximity to the pivot friction region was only slightly affected by the geometry in close proximity to the pivot bearing.…”

“…The wall shear stress increased from 0-5 Pa to 0-5, 15-20 and 75-80 Pa in the closest proximity to the pivot clearance as the Fig. 8 Surface area of the male pivot in contact with the blood pivot friction area was increased from 0 mm 2 to 1.6, 3.6 and 8 mm 2 , respectively. A slightly stagnant region occurred on the area histogram when the pivot friction area was 8 mm 2 .…”

“…8 Surface area of the male pivot in contact with the blood pivot friction area was increased from 0 mm 2 to 1.6, 3.6 and 8 mm 2 , respectively. A slightly stagnant region occurred on the area histogram when the pivot friction area was 8 mm 2 . However, this region was located far from the pivot friction area, as shown in Fig.…”

“…Thrombogenesis is closely related to low-shear flow or stagnation on the surface of the artificial material (1) . Therefore, many researchers have investigated the flow inside blood pumps using computational fluid dynamics (CFD) analysis in order to prevent thrombogenesis (2) -(6) . In our laboratory, we have developed a monopivot centrifugal pump as a ventricular assist device (7) .…”