Centrifugal pumps are non-occlusive pumps and blood flow is dependent on generated pressure and fluid viscosity. The volume pumped per RPM is afterload and preload dependent.
Roller pumps are occlusive pumps which create a constant flow by positive displacement. Volume displacement is constant at a given revolutions per minute (RPM) independent of the pressure distal to the pump, and the flow remains constant unless the RPM setting is adjusted.
The disadvantages of using a roller pump is the potential of tubing rupture if the tubing is inadvertently clamped or kinked distal to the pump. Volume displacement is also constant regardless of the volume delivered to the pump, so cavitation can occur and air can be pumped. Roller pumps cause more heat generation, and high pressure on tubing, which can cause blood trauma and hemolysis
A major benefit of using a centrifugal pump over roller pump, in regards to hemolysis, is that there is no opportunity for variability for occlusion settings like with a roller pump. Inappropriate occlusion is a major factor that causes hemolysis with a roller pump. Because a centrifugal pump is not occlusive, and no operator adjustment is necessary, the risk of hemolysis goes down with a centrifugal pump.
Other advantages to using a centrifugal pump for CPB include auto flow regulation, no spallation, and low risk of tubing rupture due to inadvertent clamping of lines or kinks. In addition, the centrifugal pumps prevent pumping of macro air, as air generates less force than blood. If the pump head deprimes, flow stops.
The disadvantage associated with these pumps is the risk of back flow or retrograde flow from the patient when the pump revolutions decrease below a critical value determined by the patient’s blood pressure.
Terumo manufactures two centrifugal pumps based on the pump head design, the CAPIOX® Disposable Centrifugal Pump and the Sarns™ Disposable Centrifugal Pump. The Terumo® Advanced Perfusion System 1 pump uses the Sarns™ Centrifugal Pump and has several integrated safety features. The flow is determined using a non-invasive flow sensor which is integrated to the Terumo System 1 to provide audible and visual alerts for low flow situations and retrograde flow. The integrated Sarns Centrifugal Pump with the Terumo System 1 provides multiple options for safety features through different pump responses, which include “stop,” “Coast™,” and “message only.” Coast™ is unique to this system and when selected as a response to an event such as low level or air, it slows the centrifugal pump speed to 1500 rpm. This stops or slows forward flow, depending on the patient’s pressure, and provides the perfusionist valuable time to identify and correct the potential emergency situation.
