Venous blood reservoir with increased level and volume sensitivity

An apparatus for preventing emptying of a blood reservoir comprising:

• a collapsible peristaltic pump including a frame, a plurality of rollers, carrier means for carrying said rollers in spaced apart relation along a predetermined path, and a pump conduit having an inlet end, an outlet end and a passageway defined therethrough, said conduit being at least partially collapsible to fully occlude at least a portion of said passageway in a free condition where pressure within said passageway is substantially equal to pressure acting on the outside of said conduit, said conduit being at least partially inflated and said passageway being open where pressure within said passageway is greater than pressure acting on the outside of said conduit;
• a blood reservoir including an inlet port permitting the inflow of blood into said reservoir and an outlet port permitting the outflow of blood from said reservoir, said reservoir further including a primary reservoir which smoothly transitions into an outlet reservoir located beneath said primary reservoir, said primary reservoir defining an upper cavity having a first average cross sectional flow area and adapted to receive and contain a first volume of blood therein, said outlet reservoir defining a lower cavity having a second average cross sectional flow area which is not more than one-half of the first average cross sectional flow area, said lower cavity having an upper level and a lower level adapted to receive and contain a second volume of blood therein which is less than said first volume of blood, said second volume of blood being a working volume usable with said pump when said primary reservoir is empty, said outlet reservoir thereby exhibiting an increased sensitivity to changes of blood volume therein relative to said primary reservoir as a result of said second average cross sectional flow of said outlet reservoir, said lower level defining said predetermined safety level below which operation of said pump is prevented;
• a connecting length of conduit coupled between said outlet port and said inlet end of said pump conduit;
• and
• blood flow stop means for stopping the flow of blood out of said reservoir to said pump when the volume of blood in said outlet reservoir reaches said safety level.