Valve mechanism for infusion fluid systems

A safety enhancement for use in an infusion fluid system for delivering and ensuring sterility and preventing contamination of a first fluid along a fluid path from a supply source that contains fresh, unused first fluid to a point of use in the infusion fluid system, the safety enhancement comprising:

• a first conduit defining the fluid path from the supply source to the point of use, the first conduit having a first branch that delivers fresh, unused first fluid to a location where the first fluid is filtered with a filter assembly and a second branch that delivers fresh, unused first fluid directly to a location where a second fluid or a third fluid is dialyzed, wherein the first conduit is split into the first and second branches at a location upstream of the filter assembly such that only the first fluid in the first branch passes through and is filtered with the filter assembly;
• a valve mechanism disposed along the first branch of the first conduit between a location where the first fluid is filtered and the point of use of the sterile first fluid such that the valve mechanism controls flow of the sterile first fluid in the first conduit, the valve mechanism being positionable between an open position in which the sterile first fluid flows through the first conduit to the point of use and a closed position in which the sterile first fluid is prevented from flowing through the valve mechanism to the point of use, wherein sterile, filtered first fluid is combined with the second fluid to form the third fluid at the point of use downstream of the valve mechanism;
• a controller that receives a first control signal representing a flow pressure of the fresh, unused first fluid at a location upstream of the valve mechanism and upstream of the filter assembly, the controller being in communication with the valve mechanism such that the controller opens the valve mechanism by sending an open control signal and closes the valve mechanism by sending a close control signal, the open control signal being sent when the first control signal exceeds a second control signal representing a reference flow pressure, the close control signal being sent under a preselected condition to prevent retrograde flow of one of the second and third fluids to a location upstream of the valve mechanism, thereby ensuring the supply source and an upstream portion of the first conduit remain substantially free of contamination by one of the second and third fluids.

A method of ensuring sterility and preventing contamination of a first fluid delivered through a first conduit from a supply source that contains fresh, unused fluid to a point of use where the first fluid is mixed with a second fluid to form a third fluid, wherein the first fluid is filtered with a substitution filter assembly before the point of use to produce sterile first fluid, the method comprising:

• disposing a valve mechanism along the first conduit, the substitution fluid filter assembly being upstream of the valve mechanism, the valve mechanism being positionable between an open position in which the first fluid flows through the first conduit to the point of use and a closed position in which the first fluid is prevented from flowing through the valve mechanism to the point of use;
• sensing a first flow pressure of the fresh, unused first fluid in the first conduit at a location upstream of the valve mechanism and upstream of the substitution fluid filter assembly;
• combining sterile, filtered first fluid with the second fluid at the point of use to form a third fluid downstream of the valve mechanism;
• opening the valve mechanism when the first flow pressure exceeds a reference flow pressure by a predetermined value;
• and closing the valve mechanism under a preselected condition to prevent the first fluid from flowing to the point of use, the closing of the valve mechanism also preventing retrograde flow of the second and third fluids from the point of use to a location upstream of the valve mechanism, thereby ensuring that the first fluid is sterile and substantially free of contamination, wherein the fluid in the first conduit is divided into a first stream that delivers fresh, unused, first fluid to the substitution fluid filter assembly where the first fluid is filtered and then delivered to the point of use and a second stream that delivers the first fluid to a device where the first fluid is used to filter the second fluid or the third fluid and the valve mechanism is disposed along
• the first stream of the first conduit between a location where the first fluid is filtered and the point of use of the sterile first fluid such that the valve mechanism acts on and controls flow of the sterile first fluid in the first conduit downstream of the location where the first fluid is filtered, where a location where the fluid is divided into the first and second streams is located upstream of the valve mechanism and substitution fluid filter assembly such that only the first stream is delivered to the substitution fluid filter assembly.