Importance

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Abstract

Apparatus and method for determining leakage, particularly of valves, in a pumping cassette. A cassette (70) includes a primary valve (34) and a secondary valve (36), which may be selectively activated to control the source of fluid input to the cassette. The cassette also includes an inlet valve (48) and an outlet valve (56) disposed on each side of a pumping chamber (52). Downstream of the outlet valve is disposed a pressure sensor (60) which produces a signal indicative of the pressure of fluid within the cassette at that point. The cassette also includes an air-in-line sensor (40), disposed between a manifold line (38) that connects the primary and secondary valve in fluid communication with an air trap reservoir (44). Leakage in the inlet or outlet valves is detected by closing both valves, pressurizing fluid in the pumping chamber for a predetermined period of time, and then opening the outlet valve. If a pressure pulse having an amplitude less than a predetermined level is detected downstream of the outlet valve when it is opened, either the inlet or outlet valve has leaked. The primary and secondary valves are checked for leakage either by pressurizing fluid in the pumping chamber and checking for retrograde flow of air trapped in the air trap reservoir through the air-in-line sensor, or by pressurizing fluid trapped in the cassette, holding the pressure for a period of time before closing the inlet valve, and then opening the outlet valve to detect a pressure pulse propagating downstream of the outlet valve, using the pressure sensor. If a pressure pulse of less than the predetermined magnitude is detected, one of the primary or secondary outlet valves is leaking. Both tests also detect leakage of other portions of the pumping cassette.

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