Patent ID: 8551044

Claim:
An implantable infusion apparatus, comprising: a housing defining a pressure chamber that contains a fluid having positive vapor pressure at normal body temperature; a first infusate reservoir defined within said pressure chamber and maintained at a positive pressure by said fluid that is external to said first infusate reservoir; a second infusate reservoir oppositely disposed to said first infusate reservoir and defined within said pressure chamber and maintained at a positive pressure by said fluid that is external to said second infusate reservoir, wherein said first and second infusate reservoirs are individually expandable to a selected portion respectively of a total available volume of the pressure chamber, the first infusate reservoir expanding in a first direction and the second infusate reservoir expanding in a second direction that is opposite the first direction; a metering assembly comprising a fixed volume accumulator having an inlet and an outlet, said accumulator comprising a chamber housing a flexible diaphragm that provides a barrier between a gas portion of the chamber and an infusate portion of the chamber; a first valve in fluid communication with said first infusate reservoir and said inlet of said accumulator; a second valve in fluid communication with said second infusate reservoir and said inlet of said accumulator; an outlet valve providing fluid communication through said outlet of said accumulator; and a control module programmed to actuate said first valve, said second valve, and said outlet valve.