Mechanical Pumps for Extracorporeal Circulation

Development of a mechanical blood pump intended to replace temporarily the function of the human heart has been the focus of physiologic and engineering research since the early 1900s. The criteria established to define the ideal blood pump during these early developmental stages are still valid. 1–3 The ideal blood pump should have a controllable pulse rate and stroke volume. It should be capable of producing a wide range of outputs which are linearly proportional to the pulse rate, but independent of the resistance to fluid flow in the perfusion circuit, including the resistance in infusion cannulas. Blood handling should occur at low velocities in order to reduce the kinetic energy transferred to the blood and thus reduce hemolysis. The pump should avoid blood stagnation, turbulence, and cavitation, and all pump parts in contact with the blood should be disposable. As a safety feature, the pump, which would be electrically controlled and operated for routine use, should have manual and/or battery operation available in the event of a power failure. Finally, the pump should include a monitoring system which can determine the actual pump speed so that this actual speed can be continuously compared to the desired pump speed set by the speed control. Table 11.1 summarizes the proposed characteristics of the ideal blood pump.