A new impeller blood pump design: in vitro and in vivo studies

Abstract

The most important design considerations in the development of a new centrifugal blood pump revolve around reductions in size and blood contact surface area, together with the production of physiological flow characteristics without undue trauma to blood proteins and formed elements. This report describes the functional testing of a centrifugal pump which weighs 240g (including a 190g motor), capable of generating a flow of 4I per minute against a pressure head of 100mmHg. Flow can be induced in both pulsatile and nonpulsatile modes. In vitro testing was conducted by comparison with a locally manufactured roller pump (Shanghai) and a Sarns 7000 pump for nonpulsatile evaluation, whilst pulsatile tests made use of a locally manufactured diaphragm pump and a Polystan pulsatile pump. Haemolysis studies showed the centrifugal pump produced only 20% and 30% red cell damage compared with the Shanghai and Sarns roller pumps respectively and in the pulsatile mode it produced only 17% and 8% of the haemolysis created by the diaphragm and Polystan pumps respectively. For in vivo testing the pump was used as an LVAD in dogs and goats and operated in both pulsatile and nonpulsatile flow modalities. Assisted flow was controlled at 40% to 50% of total flow and in nonpulsatile perfusions lasting up to 32 hours, and pulsatile perfusions lasting up to 21 hours, only very small changes were measured in haematological parameters. This study indicates that small centrifugal pumps may offer considerable advantages over the more conventional diaphragm and roller pumps with respect to pumping efficiency and blood trauma, and that careful impeller design is central to achieving optimal pump characteristics.