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Abstract

A cassette for controlling the flow of IV fluid from a patient to a source. The cassette preferably includes, along the fluid passage through the cassette, first and second membrane-based valves on either side of a pressure-conduction chamber, and a stopcock-type valve. The stopcock valve is preferably located downstream of the second membrane-based valve, which is preferably located downstream of the pressure-conduction chamber. The stopcock control valve preferably has two rigid cylindrical members with complementary surfaces, wherein one member includes a tapered groove defined on its complementary surface. The two complementary surfaces define a space therebetween, instead of having an interference fit, and a resilient sealing member is disposed in this space. When the first and second rigid members are in an open position with respect to each other, the sealing member defines an aperture through which fluid communication is provided between the fluid-path portions defined respectively by the two rigid members. When the first and second rigid members are in the closed position with respect to each other, the sealing member provides a seal preventing flow between the fluid-path portions. The membrane defining the valving chamber of the second membrane-based valve is preferably large and resilient, so that the valving chamber may provide a supply of pressurized intravenous fluid to the patient, when the valve is closed and the stopcock valve provides a restriction downstream of the valve. The pressure-conduction chamber preferably has a membrane that is stable in the empty-chamber position but relatively unstable in the filled-chamber position.

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First Claim