Comparison of Modified Chandler, Roller Pump, and Ball Valve Circulation Models for In Vitro Testing in High Blood Flow Conditions: Application in Thrombogenicity Testing of Different Materials for Vascular Applications

Three different models, a modified Chandler loop, roller pump, and a new ball valve model (Hemobile), were compared with regard to intrinsic damage of blood components and activation of platelets. The Hemobile was used for testing of polymer tubes. High flow was not possible with the Chandler loop. The roller pump and the Hemobile could be adjusted to high flow, but he pump induced hemolysis. Platelet numbers were reduced in the roller pump and Chandler loop ( ), but remained high in the Hemobile. Platelet aggregation was reduced in all models. The Hemobile was applied for testing vascular graft materials, and allowed different circuits circulated simultaneously at 37°C. ePTFE, Dyneema Purity UHMWPE fiber and PET fiber based tubes, all showed hemolysis below 0.2% and reduced platelet count and function. Binding of fibrin and platelets was higer on PET, inflammatory markers were lowest on Dyneema Purity UHMWPE. We concluded that the Hemobile minimally affects blood and could be adjusted to high blood flows, simulating arterial shear stress. The Hemobile was used to measure hemocompatibility of graft material and showed Dyneema Purity UHMWPE fiber in many ways more hemocompatible than ePTFE and PET. 1. Introduction The use of medical devices for temporary use or implantation in the blood circulation has resulted in an increased demand for evaluation of complications brought about by these devices. This resulted also in-better defined ISO requirements for testing [1] One important and relevant aspect of testing of medical devices is the condition of blood exposed to the device. Anticoagulation and flow conditions must be as similar as possible as in the clinical setting in order to achieve relevant test results. For some devices, including grafts, stents, and catheters, this implies similar anticoagulation treatment as used in clinical situations, but also high flow through or around the device to obtain relevant shear stress conditions [2, 3]. However, in some reports, blood was treated with other anticoagulants than in clinical situations. In addition, test devices were incubated under static conditions [4–7]. Flow models for testing may consist of animal models or in vitro test systems. Animal models should be avoided if equally quality results may be obtained in other ways. In addition, animal blood has essential differences compared with human blood, particularly with regard to clotting and platelet function. Two types of in vitro flow models (often with human blood) have been used extensively: the modified Chandler loop and the roller pump