Abstract: An implantable stimulation electrode having differing stiffness characteristics along its length. An endocardial electrode (20) is disclosed which includes a spirally-wound, unifilar, continuous portion (50) extending the entire length of the electrode and a stiffening portion (52) which extends for only a portion of the electrode length. The spirals of the stiffening portion (52) and the continuous portion (50) are interleaved in a juxtapositional relationship with respect to each other to form a bifilar section (26), the remainder of the electrode being a unifilar section (28). In the bifilar section (26), each spiral is wound at twice the pitch of the spirals in the unifilar section (28). The bifilar section (26) has a greater stiffness than the unifilar section. In a specific embodiment disclosed, an atrial J electrode is formed in which the bifilar section includes the J portion of the electrode where stiffness is needed.

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.