Flow control system

A perfusion system comprising:

• an extracorporeal venous reservoir;
• a flexible tube configured as a venous blood line for allowing blood from a patient to be drained through the flexible tube into the extracorporeal venous reservoir;
• a pump configured to circulate blood from the extracorporeal venous reservoir via a main blood line towards an outlet;
• two rotatable bobbins, each bobbin comprising a tube-engaging surface portion, wherein the tube-engaging surface portions define boundaries of a free space between the bobbins through which the flexible tube may extend, and wherein at least one tube-engaging surface portion has a shape that changes around at least part of a circumference of the bobbin, such that axial rotation of the bobbins rolls the bobbins along the flexible tube and modifies the free space to allow the flexible tube provided in the free space to be squeezed by an amount dependent on the rotation of the bobbins, so as to deform the tube sufficiently to affect flow through the tube;
• a flow sensor configured to determine a flow value indicative of a flow rate through the flexible tube;
• and
• a controller configured to process the flow value and programmed with control logic configured to:
• generate, for a given setup of the tube and the bobbins, a mapping between a maximum flow rate through the tube and either (i) a degree of bobbin rotation, or (ii) a position along the tube-engaging surface portion;
• receive, as an input, a flow rate restriction threshold;
• convert the flow rate restriction threshold to either (i) an amount of bobbin rotation, or (ii) a position along the tube-engaging surface portion;
• rotate the bobbins according to either (i) the amount of bobbin rotation, or (ii) the position along the tube-engaging surface portion;
• and
• switch to a closed-loop control in which the flow value from the flow sensor is used to adjust the amount of bobbin rotation to maintain a flow rate that does not exceed the flow rate restriction threshold.