Single needle alternating flow blood pump system

In blood pump including a guide for receiving a liquid-carrying tube, a rotor carrying rollers for bearing against said tube, and rotor drive means for rotating said rotor, the improvement comprising an attachment for said pump adapting said pump for use in a system for alternately withdrawing and returning blood via a single path, said attachment including:

• mounting means for attachment relative to said blood pump,
• an actuating arm pivotable with respect to said mounting means and having a first portion disposed in a path generated by a portion of said rotor whereby rotation of said rotor to a predetermined position pivots said arm from a first position to a second position,
• a spring normally biasing said arm into said first position to be actuated by said rotor,
• a clamping member disposed adjacent said arm and receiving a length of tubing between said arm and said clamping member such that said arm in its first position compresses said tubing against said clamping member and in said second position unclamping said tubing,
• said tubing communicating with said liquid-carrying tube,
• switching means operated by movement of said arm to said second position, said switching means being connected for interrupting power to said drive means for said pump, whereby said arm is effective for unclamping said tubing while said power is interrupted,
• and means for subsequently restoring power to said drive means for reinitiating pumping by said pump.