Importance

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Abstract

A fluid flow monitoring method and device for a drug injector (10). More particularly, a flow monitoring device is disclosed for an implantable or externally located drug injector having a conduit (18) for carrying fluid from a reservoir (14) to a user's body. In an exemplary embodiment, the drug injector (10) is of the type having a first valve (22) located proximal to the reservoir (14) for blocking the flow of fluid through the conduit (18), a second valve (24) located distal to the reservoir (14) for blocking the flow of fluid through the conduit (18), and a pump (20) located between the first and second valves (22) and (24) for alternately increasing and decreasing the volume of a conduit portion (68) located between the first and second valves (22) and (24). The valves are controlled so that the first valve (22) is open and the second valve (24) closed when the pump (20) is increasing the volume of its associated conduit portion, thereby drawing fluid from the reservoir (14) into the conduit (18). The valves are further controlled so that the first valve (22) is closed and the second valve (24) open when the pump (20) is decreasing the volume of its associated conduit thereby forcing fluid from the conduit (18) into the user's body. The fluid flow monitoring device includes circuitry for generating signals related to the electrical resistance of the fluid across the first and second valves (22) and (24), and the conduit portion (68) whose volume is affected by the pump (20). These signals are utilized to continually determine the configuration of each valve and the volume of the conduit portion (68). This information can be utilized to calculate fluid flow through the conduit (18).

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First Claim