Variable flow implantable infusion apparatus

Abstract

Implantable variable flow infusion apparatus comprises a collapsible infusate chamber having an outlet conduit leading to the infusion site by way of series-connected fixed and variable fluid flow restrictors. The infusate in the chamber is maintained under substantially constant pressure by a nonelectric energy storage cell to establish flow from the chamber to the site. The variable restrictor is controlled by commands from a preprogrammed microprocessor and programmable memory powered by a small long-lived battery. The processor sets the variable restrictor to the proper setting to establish the correct infusate flow for the particular time of day. A pressure transducer connected across the fixed restrictor senses the pressure differential across the fixed restrictor which differential indicates actual infusate flow from the chamber. The processor samples the output from the transducer at infrequent sampling intervals and issues command signals to control the variable restrictor whenever the actual infusate flow rate differs from the preprogrammed rate so that the apparatus consumes a minimal amount of battery energy and can thus remain implanted in the body for a prolonged period. The processor can also be reprogrammed and monitored by telemetry.