Rechargeable tissue stimulating system

• US 3,942,535 A
• Filed: 07/26/1974
• Issued: 03/09/1976
• Est. Priority Date: 09/27/1973
• Status: Expired due to Term

• Current Assignee: Siemens-Elema AB (Siemens AG)
• Original Assignee: GD Searle LLC (Pfizer Inc.)
• Inventors: Schulman, Joseph H.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/491,974
• Time in Patent Office: 592 Days
• Field of Search: 128/2.05 S, 128/2.06 E, 128/2.1 A, 128/418, 128/419 C, 128/419 EP, 128/419 PG, 128/419 PS, 128/419 R, 128/420, 128/421, 128/422, 128/423 , 128/419 PT, 307/91, 320/31, 320/32, 320/37, 320/39, 328/84, 336/84
• US Class Current: 607/33
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A rechargeable tissue stimulating system with a telemetry controlled power source. A constant current power source acting through an induction coil externally located with respect to a living patient is used to induce current flow in a charging circuit located beneath the skin of the patient. The charging circuit, in turn, recharges a battery which powers an electronic generator used for applying electrical pulses to stimulate living tissue in order to maintain bodily functions in the patient. A telemetry circuit connected to the charging circuit provides a magnetic output signal controlling externally located means associated with the power source. Such external means in response to this signal modulate the strength of the charging magnetic field, as well as provide visual or audio indication of proper charging as well as the proper positioning of the external power source with respect to the implanted charging circuit, completion of the proper charging interval to restore the amount of current used, and improper charging.

Claims

1. A rechargeable tissue stimulating system comprising:

means for implantation in the body of a living subject for applying electrical pulses to stimulate living tissue in order to maintain bodily functions of said subject, said means including a rechargeable DC voltage source supplying the power for said pulses;

internal charging means for implantation beneath the skin of said subject and connected to said source for providing a charging current to said voltage source, said internal charging means including a first induction coil;

an external means for supplying power by induction to said internal charging means and including a second induction coil for setting up a magnetic field and for positioning external to a living subject and proximate to said first induction coil;

telemetry means connected to said internal charging means for detecting the magnitude of said charging current received by said DC voltage source and providing a magnetic output signal to said external power source indicative of the magnitude of said charging current; and

transducer means forming a part of said external means for supplying power for converting said magnetic output signal to an electrical signal, and including current control means responsive to said electrical signal for adjusting the strength of the magnetic field applied to said internal charging means in response to changes in said electrical signal, such that the magnitude of said charging current is maintained within predetermined limits.

2. The tissue stimulating system of Claim 1 in which said first induction coil includes first and second output leads, and wherein said internal charging means further comprises first and second diodes respectively in series with said first and second output leads to rectify the output of said first induction coil,

a current sampling resistor means connected in series to one of said diodes on the side opposite said first coil, and

a shunt current regulator connected between the other of said diodes on the side opposite said first coil, and to said current sampling resistor on the side opposite said one diode, said regulator including a current shunting transistor with the collector thereof in series with said current sampling resistor, the emitter thereof connecting with said other diode, said regulator also including a shunt resistor biasing the base of said transistor and connected across the emitter and base thereof.

3. The tissue stimulating system of claim 2, wherein the implantable charging circuit further comprises a third diode in series with either of said first and second diodes, to prevent said internal charging means from draining current from said DC voltage source in the event of a short in said internal charging means.

4. A rechargeable cardiac pacing system for maintaining stimulating pulses to the heart of a patient comprising:

means for positioning beneath the skin of a patient for applying stimulating pulses to the heart of the patients, including a rechargeable DC voltage source, and catheter means, said catheter means including electrodes connected to said pulse generating circuits;

means for internal positioning beneath the skin of a patient for recharging said DC voltage source and including a first induction coil;

an external means for supplying power by induction to said internal recharging means, said external means including a second induction coil for external positioning with respect to the patient proximate to the first induction coil;

telemetry means connected to said internal recharging means for detecting the magnitude of a charging current received by said DC voltage source, and for providing a magnetic output signal indicative thereof;

timing means responsive to said magnetic output signal and including means for storing a signal indicative of time elapsed during which the magnetic output signal indicates that the charging current is at least as great as a predetermined minimum operating level.

5. The cardiac pacing system of claim 4 wherein said means for storing comprises a register and said timing means further includes transducer means for converting said magnetic output signal to an electrical signal, a comparator for providing a timing signal when actuated by a magnetic output signal exceeding a predetermined minimum level, and time recorder means connected to actuate said register for recording time elapsed during which a timing signal is received thereby.

6. The cardiac pacing system of claim 5 wherein said timing means further includes a dividing means connected to said register operative to tabulate a number of identical charging periods of uniform duration in said register.

7. The cardiac pacing unit of claim 6 wherein said register is further provided with means for generating an audio output each time a charging period is recorded in said register.

8. The cardiac pacing system of claim 4 wherein said register decrements as well as increments and includes inputs corresponding thereto, with said time recorder means being connected to said decrementing input, and wherein said timing means further comprises clock means connected to said incrementing input, whereby said register counts the discharged time intervals during which said rechargeable DC source discharges during its normal use, as well as the charging time intervals during which said DC source receives said timing signal indicative of proper charging, said register offsetting said discharge and charge intervals against each other to indicate the remaining recommended recharging time needed to fully restore said DC source.

9. The cardiac pacing system of claim 8 in which said time recording means includes an oscillator and a first AND gate in which said oscillator is in series with one input of said gate, the second input of said gate receiving said timing signal, and in which said timing means also includes said oscillator as well as a second AND gate, with said oscillator being in series with one input of said second gate, and the output of said first gate being connected to the other input of said second gate, as well as in series with said decrementing register input, and the output of said second gate being in series with said incrementing input, whereby the occurrence of one of said timing signals inhibits the output of said clock means.

10. The cardiac pacing unit of claim 8 wherein said register includes means for furnishing a limit signal either upon the occurrence of a predetermined maximum increment, or upon the occurrence of a decrement to zero, and in which said timing means further includes limit alarm means connected to said register and responsive to said limit signal to warn of an unacceptable charge or discharge state.

11. The cardiac pacing system of claim 4 further including means for generating an audio signal actuated by operation of said means for supplying power and connected to said telemetry means, said audio signal generating means further including means for disabling said audio output in response to a magnetic output signal indicative of a charging current at least as great as a predetermined minimum operating level.