Abstract: The present invention is an introducer catheter apparatus having a body with a first bore along a longitudinal axis and a second bore in fluid communication with the first bore and extending from the first bore to the exterior surface at the side of the body, a fluid delivering means disposed on the second bore as the exterior surface of the body and the fluid communication with the second bore, and a flexible hollow tube means disposed in the first bore, a deformable sealing means disposed in the first bore between the second end of the body and the position within the first bore where the second bore connects to the first bore and a retractable needle means extends through the body including the deformable sealing means and a flexible hollow tube means and the tip of said needle when therein disposed extends past a distal end of the flexible hollow tube means.

Abstract: The present invention is a sensing amplifier circuit for a tissue stimulator (72) for supplying or attenuating far field signal voltage artifacts comprising a full differential amplifier having a first (94, 136) and second (96, 142) stage amplifiers for respectively receiving a second and first signal voltage output from a sensing mean (80, 82), and a switch means for controlling an input of the second signal voltage output from said sensing means to the first stage amplifier (94, 136).

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).

Abstract: A method and apparatus for monitoring the status of a battery in an implantable device for a human, the device being a tissue stimulator, drug dispensing apparatus, or the like. More specifically, a battery monitoring apparatus is disclosed whereby a user is sensually stimulated whenever an implanted battery exhibits predetermined characteristics. In one embodiment, the internal resistance of a battery is periodically monitored by loading the battery at predetermined intervals. When the internal resistance exhibits a predetermined characteristic, a battery alarm circuit is activated which causes a small voltage differential to be applied under and across the skin of the user, thereby creating a mildly tingling sensation in his skin. This tingling sensation alerts the user that the battery needs to be replaced or recharged. A magnet is provided for externally disabling the monitoring apparatus after the user has been alerted that the battery needs replacement.

Abstract: A magnetic field concentration means and method for use in conjunction with an implanted device responsive to an externally generated magnetic field. More specifically, a magnetic field concentrator is disclosed which includes a metallic slug located between a magnetic field generator and a magnetic pick-up coil contained in the implanted device. The metallic slug concentrates magnetic lines of flux at the pick-up coil. In a specific embodiment, the implanted device is an intracranial pressure monitoring device (ICPM) which is located within an orifice formed in a recipient's skull. The magnetic field concentrator is positioned within the orifice and directly above the ICPM, thereby concentrating magnetic flux lines at the ICPM. Two configurations of the slug are disclosed, one being in the form of a cylinder and the other being in the form of a truncated cone.

Abstract: A battery monitoring means for an implantable tissue stimulator in which a signal related to the internal impedance of an implanted battery is telemetered to an external receiving means. More specifically, the implanted battery is loaded by a varible load until current flowing through the battery lowers its output voltage until it has a predetermined relationship with respect to a reference voltage. The current flowing through the battery to achieve the predetermined relationship is directly related to the internal impedance of the battery. A voltage related to the value of this current is then telemetered to the external receiving means. In a specific embodiment, the variable load is a field effect transistor (FET) connected as a source follower. The impedance of the FET is controlled by the output of an operational amplifier having as inputs the reference voltage and a voltage related to the output voltage of the battery.

Abstract: An apparatus and method for displaying and controlling parameters for a programmable living tissue stimulator system. Visual indicators corresponding to control parameters or signals for the tissue stimulator system are divided into a predetermined number of groups. One of these groups containing a parameter to be selected for the tissue stimulator system is selected, the selected group being identified by a visually identifiable indication. A parameter within that group is then selected for transmission to an implanted memory means which controls an implanted tissue stimulator. In a specific embodiment, a matrix of visual indicators consisting of R rows and S columns is provided, each visual indicator corresponding to a specific control signal. A means is provided whereby at least one visual indicator contained in a selected R row will blink on and off, the blinking indicators identifying control signals to be selected for the implanted memory means.

Abstract: An implantable body transducer having a self-contained calibration means. An exemplary embodiment comprises an implantable body pressure measuring transducer utilizing an L-C oscillator having a resonant circuit comprising a fixed L and a variable C, the variable C having a fixed capacitive electrode and a movable capacitive electrode in the form of a stiff pressure responsive diaphragm, the output frequency of the oscillator being a function of the pressure sensed by the diaphragm. The transducer incorporates a self-contained calibration means which contains predetermined calibration data with respect to the variable C. The predetermined calibration data is stored in a plurality of PROM storage elements which are sequentially addressed in accordance with the output of a counter, the PROM storage elements providing a serial bit stream which can be used to pulse-code modulate the L-C resonant circuit output.

Abstract: A battery life extender for use in an implantable tissue stimulator. The tissue stimulator comprises a battery which powers a volatile memory, control circuits and a pulse output circuit all of which are connected in parallel across the battery. The invention provides a means for controlling current through the output circuit as a function of a difference voltage between the battery output voltage and a reference voltage. The reference voltage and battery voltage comprise inputs to a differential amplifier which in turn provides an output control voltage which controls a field-effect transistor (FET) connected in series with the output circuit and battery. As this control voltage rises, current through the field-effect transistor is reduced, thereby reducing the amplitude of the pulses from the output circuit and the current drain from the battery.

Abstract: An implanted heart and tissue stimulator is provided which is externally programmable so that stimulating signals generated thereby can be changed to meet the changing requirements of the user. Provision is made for verifying and screening control parameter words which are transmitted from an external controller so that only correct parameters will be stored for use by the implanted stimulator. Provision for read out of stimulating signals and of the tissue response thereto is also provided.

Abstract: A battery monitoring means for an implantable living tissue stimulator system in which various battery voltages are telemetered to an external receiving means, these voltages being related to the internal impedance of the implanted battery. More specifically, a battery loading circuit is provided which incorporates a switch means for loading the battery in accordance with a predetermined sequence. In a specific embodiment, first and second resistors are sequentially connected across the battery. The battery output voltage is telemetered to an external receiving means during this sequential connection. By knowing the values of the two resistors, the internal impedance of the battery can be calculated, this impedance being related to the remaining life of the implanted battery.

Abstract: A telemetry system for use in a living tissue stimulator system in which an externally located oscillator is controlled by impedance changes in an impedance reflecting circuit located in an implantable tissue stimulator. In a first embodiment the impedance reflecting circuit is an LC circuit thereby frequency modulating the externally located oscillator and in a second embodiment it is an LR circuit thereby amplitude modulating the externally located oscillator. More specifically, the externally located oscillator drives an LC circuit in which the inductor is positioned in magnetically coupled relationship to an inductor in the impedance reflecting circuit. The externally located oscillator is chosen so that its frequency and amplitude is partially determined by the impedance of the LC circuit and the magnetically coupled impedance reflecting circuit.

Abstract: An implantable AM receiver having a variable threshold which can detect signals above a changing noise level. An AM receiver is provided which provides a modulation envelope corresponding to the amplitude of a pulse-modulated RF signal radiated by an external device. A voltage signal is developed which is at least equal to the amplitude of the modulation envelope, but which decays at a predetermined rate if the modulation envelope drops to a value below the voltage signal. The voltage signal is then scaled to a predetermined percentage of a value corresponding to the value of the modulation envelope, and biased so that it cannot drop below a predetermined minimum level. The scaled voltage signal comprises the variable threshold and is compared by a comparator to the modulation envelope. If it is below the modulation envelope, the comparator outputs a voltage having a first state; if it is above the modulation envelope, the comparator outputs a voltage having a second state.

Abstract: In an implantable human tissue stimulator with a volatile memory an arrangement is provided to protect against the stimulating circuitry producing pulses as a function of unknown parameters in the memory, as a result of inadequate power to the memory from a rechargeable power source, e.g. a rechargeable battery. The arrangement includes voltage sensors, so that when the voltage from the battery drops below a selected level the stimulating circuitry is disconnected from the battery and only the memory is powered. If the voltage from the battery first drops, so that insufficient power is supplied to the memory and thereafter rises, as a result of recharging, to a level sufficient to power the memory, the memory is first reset with known parameter values. Only thereafter when the voltage level reaches the selected level, is the rest of the circuitry, including the stimulating circuitry, reconnected to the battery.

Abstract: A system is disclosed for controlling the charging of a rechargeable battery in an implanted human tissue stimulator by means of an external power source. Included in the stimulator are battery protection devices designed to sense the state of charge of the battery and limit the charging currrent amplitude so as not to exceed a selected maximum based on different criteria including battery state of charge signals from the implanted stimulator which are indicative of the current amplitude and battery state of charge from one of the protection devices are transmited to an external unit. Based on these signals the external unit is operated in one of a plurality of modes to cause the battery to be charged by a current with an optimum safe amplitude irrespective of determined failure of one or more of the battery protection devices.

Abstract: An implantable living tissue stimulator is described with a current conductive protective shield, to prevent the flow of currents to or from the stimulator circuitry via the electrically conductive body fluid. Also disclosed is an implantable living tissue stimulator of the rechargeable type in which the stimulator circuit components are surrounded by a pickup coil, designed to pick up an external magnetic field for recharging the power source, e.g., battery of the stimulator. One embodiment incorporates one or more ferrite slabs extending through the coil wound about the rest of the stimulator components, in order to increase the coil pick up efficiency and to divert the magnetic field from the stimulator metal components, such as a metal container in which the stimulator circuitry is hermetically sealed and thereby minimize the heating of the components and/or metal container.

Abstract: An implantable hermetically sealed living tissue stimulator which includes a coil in which current is induced by an external alternating magnetic field is disclosed. All the stimulator circuit components except for one or more electrode leads are hermetically sealed within a hermetic container formed of a biocompatible metal of a thickness T, and having an electrical resistivity .rho., where T/.rho. .ltoreq. 0.03, T being in mils and .rho. in microhm-cm. The metal thickness T is not more than 5 mils and preferably not more than 3 mils, and the electrical resistivity .rho. is not less than 75 microhm-cm and preferably not less than 100 microhm-cm, in order to reduce the portion of power induced in the stimulator by the magnetic field which is dissipated as heat in the hermetic metal container and to increase the portion of the induced power which penetrates the container and induces the current in the coil.

Abstract: A myocardial lead for applying electrical pulses to a myocardium includes a relatively large electrode body of a metal, exhibiting high stress fatigue and corrosion resistance properties, a short stud of a metal containing platinum is partially inserted into the electrode body, with the stud portion extending out of the body defining the electrode pin. The stud is electron beam welded to the body. The myocardial lead also includes a distal wire, which consists of a plurality of flexible wire coils of the same metal as the electrode body and are covered by a flexible rubber sleeve. At one end, the wire coils pass through a cavity in the electrode body, with the coils' portion extending therefrom being wrapped around the electrode body and welded thereto. The distal wire extends to a source of electrical pulses. A platinum winding is wrapped around the electrode pin and is attached at one end to the electrode body.