• Pulsatile flow may be defined as flow which is subject to
periodic variations in velocity
• Roller pumps normally deliver pulsatile flow, but the pulses are
of such low amplitude and high frequency, depending on the degree of occlusion,
number of rollers on the pump head and the RPM. This normally produced
pulsatile flow by roller pumps is usually rapidly eliminated by damping in the
arterial tree
• Accelerated-cycle roller pumps have been designed to produce
pulsatile flow. The roller travel speed is first accelerated, then slowed to
give pulsatility [“hurry-up-and-wait” mode of operation].
• The amplitude, frequency and duration of the pulse wave can be
varied from the control console. The system may be triggered internally or by
the ECG.
• It is adjustable in stroke volume by controlling the
speed when it is on and by changing to larger or smaller internal diameter
tubes in the pump head.
• Pulse rate is controlled by the number of “off” periods
per minute
• During the acceleration of the roller pump phase, high inlet
suction and severe tubing wall contact could be haemolytic
• During the acceleration of the roller pump phase, excessive
shear stresses (and high Reynold number) may occur in region of arterial
cannulae