Importance

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Abstract

An IV pump actuates a disposable cassette having two parallel fluid paths that include first and second pumping chambers. The disposable cassette (12) has a housing(14) that includes a back portion (152) in which is defined a fluid path (60) between an inlet port (16) and an outlet port (18). An elastomeric membrane (150) is sealed between the back portion and a front portion (52). The elastomeric membrane is exposed through the front portion at a first pumping chamber (82), a second pumping chamber (84), inlet valves (70, 76), and outlet valves (86, 92). The inlet valves operate in a fully open mode, a fully closed mode, and a cracking mode. The cracking mode of the inlet valve occurs as the elastomeric membrane is initially forced further into the pumping chamber. If the pressure of the fluid in the pumping chamber exceeds a predetermined cracking pressure, the inlet valve is forced open so that the fluid flows from the pumping chamber back toward the inlet port. The inlet valve then fully closes and fluid flows through the outlet valve. Since fluid is forced alternatively from the first and second pumping chambers, the flow from the outlet port is substantially continuous. During the pumping stroke, operation of the inlet valves in the cracking mode compensates for variations in the proximal pressure. The outlet valves can also be operated in a cracking mode to compensate for variations in the pressure distal to the cassette.

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First Claim