Abstract: A medical device known as an implantable therapeutic substance delivery device is configured for implanting in humans to deliver a therapeutic substance such as pharmaceutical compositions, genetic materials, and biologics to treat a variety of medical conditions such as pain, spastisity, cancer, and many other conditions. The infusion device embodiment has active longevity projection that more accurately predicts an elective replacement period for the infusion device to increase the infusion device's effective life, reduce the need for a clinician to perform static longevity forecasts for therapy changes, facilitate elective replacement scheduling for the convenience of the patient and clinician, and many other improvements. The infusion device has a housing, a power source, a therapeutic substance reservoir, a therapeutic substance pump, and electronics. Many embodiments of the therapeutic substance delivery device with active longevity projection and its methods of operation are possible.

Abstract: Reservoir volume in a drug delivery device is sensed by providing a capacitor, the capacitance of which varies with bellows position or, alternatively, with the amount of propellant liquid absorbed in a dielectric material. In one embodiment, a capacitance is provided between a surface of the bellows, which acts as a first capacitor plate, and a conductive surface disposed proximate the bellows, which acts as a second capacitor plate. As the bellows moves from its extended full position to its collapsed empty position, the area of overlap, and therefore the capacitance between the first and second plates varies from a maximum value to a minimum value. In another embodiment, a variable capacitor is provided with an absorbent material. The absorbent material absorbs the liquid phase of the propellant in the pump housing and acts as a dielectric between two stationary conductive plates provided in the housing. The amount of liquid propellant absorbed in the absorbent material varies with the reservoir volume.

Abstract: An implantable system for treating a patient by an implantable electrical transducer and an implantable and rechargeable power source comprising a capacitive energy storage unit. A circuit is provided for recharging the power source without removing the power source from the patient. The power source preferably comprises a capacitor having a rating of at least 0.1 farads fabricated from carbonized phenol fibers.

Abstract: High frequency transmitter and receiver circuits are AC coupled for party line transmission over coaxial cable where the circuits are connectable to the cable by use of stinger taps and thereby eliminate the need to interrupt service when connecting the circuits to the cable. The transmitter circuit includes oppositely polled current sources which are alternately switched to the coaxial cable via the stinger tap or to a dummy load by current switches connected to data inputs via buffer circuits. A transmit enable circuit controls the current sources to be active or inactive and to prevent unbalances from saturating either current sources. The receiver includes a high input impedance biasing network and buffer amplifier that maintain the high input impedance even when power is off. Capacitance at the tap is reduced by a capacitor drive circuit which feeds input signal back to transmitter blocking diodes and to the trunk tap.