Defibrillator circuit for producing a trapezoidal defibrillation pulse

• US 4,823,796 A
• Filed: 04/03/1987
• Issued: 04/25/1989
• Est. Priority Date: 04/03/1987
• Status: Expired due to Fees

• Current Assignee: Laerdal Manufacturing Corp.
• Original Assignee: Laerdal Manufacturing Corp.
• Inventors: Benson, Jonathan M.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US07/034,487
• Time in Patent Office: 753 Days
• Field of Search: 128/419 D
• US Class Current: 607/7
• CPC Class Codes: A61N 1/3904 External heart defibrillators [EHD]
• CPC Class Codes: A61N 1/3906 characterised by the form of the shockwave
• CPC Class Codes: A61N 1/3912 Output circuitry therefor, e.g. switches

Abstract

A pulse delivery control signal is applied to and removed from a master or pulse delivery electronic switch to respectively start and terminate the delivery of a trapezoidal waveform defibrillation pulse from charge storage capacitors to a patient. In one specific embodiment, a transfer charge storage circuit is coupled to a capacitor charging circuit for charging as the charge storage capacitors are charged. A transfer switch interconnects the transfer charge storage circuit to a first field-effect transistor switch. In response to a transfer signal, a transfer voltage signal is delivered from the transfer charge storage circuit, through the transfer switch and to the first field-effect transistor. In response, the first field-signal transistor applied the pulse delivery control signal to the master switch. A second field-effect transistor may be included for operating the master switch together with the first field-effect transistor. Voltage detection and energy selection circuits may be employed for detecting when the charge storage capacitors in the circuit are charged to a desired level and for establishing the level to which the capacitors are charged to thereby control the energy delivered by the defibrillation pulses.

Claims

1. A defibrillator circuit for applying trapezoidal defibrillation pulses to a patient comprising:

means for producing a defibrillation pulse delivery control signal;

capacitor charge storage means;

charging circuit means for charging the capacitor charge storage means;

defibrillation pulse discharge circuit means for coupling the capacitor charge storage means in series with the patient and for selectively delivering a trapezoidal-shaped defibrillation pulse from the capacitor charge storage means to the patient, the discharge circuit means including a first electronic defibrillation pulse delivery switch means in the series path, the first pulse delivery switch means comprising means for shifting to a first conducting state in response to a defibrillation pulse delivery control signal to permit the partial discharge of the capacitor charge storage means through the patient, the first pulse delivery switch means also comprising means for shifting to a second non-conducting state when the pulse delivery control signal is removed to block further discharge of the capacitor charge storage means through the patient, the discharge circuit means including defibrillation pulse delivery control means for selectively delivering the pulse delivery control signal to and removing the pulse delivery control signal from the first pulse delivery switch means to thereby respectively commence and terminate the application of a defibrillation pulse to the patient.

2. A defibrillation circuit according to claim 1 in which the first pulse delivery switch means comprises a Darlington pair of transistor means for shifting to the first conducting state is response to the defibrillation pulse delivery control signal and to the second non-conducting state when the pulse delivery control signal is removed.

3. A defibrillator circuit according to claim 1 in which the defibrillation pulse delivery control means includes means for generating a defibrillation pulse transfer signal and control circuit means responsive to the transfer signal for selectively applying the pulse delivery control signal to and removing the pulse delivery control signal from the first pulse delivery switch means to thereby respectively commence and terminate the application of a defibrillation pulse to the patient.

4. A defibrillator circuit according to claim 3 in which the control circuit means includes first transfer switch means operatively coupled to the first pulse delivery switch means for applying the pulse delivery control signal to the first pulse delivery switch means upon the application of the transfer signal to the first transfer switch means.

5. A defibrillator circuit according to claim 4 in which the first transfer switch means comprises a first field-effect transistor circuit means, the control circuit means also including a second field-effect transistor circuit means coupled to the first pulse delivery switch means and to the first field-effect transistor circuit means for driving the first pulse delivery switch means into a conducting state in response to the transfer signal.

6. A defibrillator circuit according to claim 4 in which the first pulse delivery switch means comprises a cascode switch.

7. A defibrillation circuit according to claim 3 in which the control circuit means includes first transfer switch means operatively coupled to the first pulse delivery switch means for applying the pulse delivery control signal to the first pulse delivery switch means in response to the transfer signal, transfer charge storage circuit means for providing a first transfer switch control signal, second transfer switch means responsive to the transfer signal for selectively coupling the transfer storage circuit means to the first transfer switch means to apply the first transfer switch control signal to the first transfer switch means, the first transfer switch means comprising means for applying the pulse delivery control signal to the first pulse delivery switch means in response to the first transfer switch control signal and thereby in response to the transfer signal.

8. A defibrillator circuit according to claim 7 in which the transfer charge storage circuit means is coupled to the charging circuit means for charging by the charging circuit means as the capacitor charge storage means is charged.

9. A defibrillator circuit according to claim 8 in which the discharge circuit means includes second defibrillation pulse delivery switch means in the series path including the capacitor charge storage means and patient, the second pulse delivery switch means comprising means for closing the series path through the second pulse delivery switch means prior to the application of the pulse delivery control signal to the first pulse delivery switch means and for opening the series path through the second pulse delivery switch means following the application of the pulse delivery control signal to the first pulse delivery switch means.

10. A defibrillator circuit according to claim 1 including energy selection circuit means for selecting the energy to be delivered to a patient by the trapezoidal-shaped defibrillation pulse.

11. A defibrillator circuit according to claim 1 including voltage detection circuit means having means for establishing a reference threshold voltage, the voltage detection circuit means comprising means for comparing the voltage on the capacitor charge storage means to the reference threshold voltage and for indicating that the voltage on such capacitor charge storage means has reached the threshold.

12. A defibrillator circuit according to claim 11 in which the voltage detection circuit means comprises a voltage divider circuit coupled from the charge storage means to ground potential, a detection circuit field-effect transistor having its gate coupled to the voltage divider circuit and its drain coupled to the charge storage means, a zener diode having its cathode coupled to the source of the detection circuit field-effect transistor and its anode coupled to ground potential, and means for detecting and indicating current flow through the detection circuit field-effect transistor and thereby the charging of the charge storage means to the threshold voltage.

13. A defibrillator circuit according to claim 11 including energy selection circuit means for selecting energy to be delivered to a patient by the trapezoidal-shaped defibrillation pulse in response to the pulse delivery control signal, the energy selection circuit means comprising means for selectively varying the reference threshold voltage to thereby select the energy to be delivered to a patient.

14. A defibrillator circuit according to claim 13 in which the energy selection circuit means comprises means for generating a digital signal corresponding to the desired energy, encoder means for receiving the digital signal and for producing an encoder output signal, digital to analog converter means for receiving the encoder output signal and for producing an analog output signal which represents the threshold voltage, whereby variations in the digital signal result in a variation of the threshold voltage and in the energy delivered to a patient by the trapezoidal-shaped defibrillation pulse.

15. A defibrillator circuit for applying trapezoidal defibrillation pulses to a patient comprising:

capacitor charge storage means;

charging circuit means for charging the capacitor charge storage means;

defibrillation pulse discharge circuit means for coupling the capacitor charge storage means in series with the patient and for selectively delivering a trapezoidal-shaped defibrillation pulse from the capacitor charge storage means to the patient;

voltage detection circuit means having means for establishing a reference threshold voltage, the voltage detection circuit means comprising means for comparing the voltage on the capacitor charge storage means to the reference threshold voltage and for indicating that the voltage on such capacitor charge storage means has reached the threshold and thereby that the defibrillator circuit is ready to deliver a defibrillation pulse of a desired energy; and

energy selection circuit means for selecting the energy to be delivered to a patient by the trapezoidal-shaped defibrillation pulse, the energy selection circuit means comprising means for selectively varying the reference threshold voltage to thereby select the energy to be delivered to the patient;

the energy selection circuit means comprising means for generating a digital signal corresponding to the desired energy, encoder means for receiving the digital signal and for producing an encoder output signal, digital to analog converter means for receiving the encoder output signal and for producing an analog output signal which represents the threshold voltage, whereby variations in the digital signal result in a variation of the threshold voltage and in the energy delivered to the patient by the trapezoidal-shaped defibrillation pulse.

16. A defibrillator circuit for applying trapezoidal defibrillation pulses to a patient comprising:

capacitor charge storage means;

charging circuit means for charging the capacitor charge storage means;

defibrillation pulse discharge circuit means for coupling the capacitor charge storage means in series with the patient and for selectively delivering a trapezoidal-shaped defibrillation pulse from the capacitor charge storage means to the patient;

voltage detection circuit means having means for establishing a reference threshold voltage, the voltage detection circuit means comprising means for comparing the voltage on the capacitor charge storage means to the reference threshold voltage and for indicating that the voltage on such capacitor charge storage means has reached the threshold and thereby that the defibrililator circuit is ready to deliver a defibrillation pulse of a desired energy;

energy selection circuit means for selecting the energy to be delivered to a patient by the trapezoidal-shaped defibrillation pulse, the energy selection circuit means comprising means for selectively varying the reference threshold voltage to thereby select the energy to be delivered to the patient; and

the voltage detection circuit means comprising means for establishing a ground potential, a voltage divider circuit coupled from the charge storage means to ground potential, a detection circuit field-effect transistor having its gate coupled to the voltage divider circuit and its drain coupled to the charge storage means, a zener diode having its cathode coupled to the source of the detection circuit field-effect transistor and its anode coupled to ground potential, and means for detecting and indicating current flow through the detection circuit field-effect transistor and thereby the charging of the charge storage means to the threshold voltage.

17. A defibrillator circuit for applying trapezoidal defibrillation pulses to a patient comprising:

capacitor charge storage means;

charging circuit means for charging the capacitor charge storage means;

defibrillation pulse discharge circuit means for coupling the capacitor charge storage means in series with the patient and for selectively delivering a trapezoidal shaped defibrillation pulse from the capacitor charge storage means to the patient, the discharge circuit means including a first electronic defibrillation pulse delivery switch means in the series path, the first pulse delivery switch means comprising means for shifting to a first conducting state in response to a control signal to permit the partial discharge of the capacitor charge storage means through the patient, the first pulse delivery switch means also comprising means for shifting to a second non-conducting state when the pulse delivery control signal is removed to block further discharge of the capacitor charge storage means through the patient;

the discharge circuit means including defibrillation pulse delivery control means for selectively applying the pulse delivery control signal to and removing the pulse delivery control signal from the first pulse delivery switch means to thereby respectively commence and terminate the application of a defibrillation pulse to the patient, the defibrillation pulse delivery control means including first field-effect transistor circuit means coupled to the first pulse delivery switch means for applying the pulse delivery control signal to the first pulse delivery switch means upon the application of a transfer voltage signal to the first field-effect transistor circuit means, transfer charge storage circuit means for providing the transfer voltage signal, transfer switch means for selectively coupling the transfer charge storage means to the first field-effect transistor circuit means to apply the transfer voltage signal to the first field-effect transistor circuit means so as to apply the pulse delivery control signal to the first pulse delivery switch means, the control circuit means also including second field-effect transistor circuit means coupled to the first pulse delivery switch means and to the first field-effect transistor circuit means for applying the pulse delivery control signal to the first pulse delivery switch means to drive the first pulse delivery switch means into a conducting state upon application of the transfer voltage signal to the first field-effect transistor circuit means.

18. A defibrillator circuit according to claim 17 in which the transfer charge storage means is coupled to the charging circuit means for charging by the charging circuit means as the capacitor charge storage means is charged.

19. A defibrillator circuit according to claim 18 in which the discharge circuit means includes second pulse delivery switch means in the series path including the capacitor charge storage means and patient, the second pulse delivery switch means comprising means for closing the series path through the second pulse delivery switch means prior to the application of the pulse delivery control signal to the first pulse delivery switch means and for opening the series path through the second pulse delivery switch means following the application of the pulse delivery control signal to the first pulse delivery switch means.

20. A defibrillator circuit according to claim 19 in which the first pulse delivery switch means comprises a cascode switch.

21. A defibrillator circuit according to claim 18 including voltage detection circuit means for comparing the voltage on the capacitor charge storage means to a reference threshold voltage and for indicating the voltage on such capacitor charged storage means has reached the threshold.

22. A defibrillator circuit according to claim 21 including energy selection circuit means for selecting the energy to be delivered to a patient by the trapezoidal-shaped defibrillation pulse.

23. A defibrillator circuit according to claim 22 including abort circuit means for discharging the capacitor storage means in the event treatment of a patient with defibrillation pulses is unnecessary.

24. A defibrillator circuit according to claim 23 in which the discharge circuit means includes second pulse delivery switch means in the series path including the capacitor charge storage means and patient, the second pulse delivery switch means comprising means for closing the series path through the second pulse delivery switch means prior to the application of the pulse delivery control signal to the first pulse delivery switch means and for opening the series path through the second pulse delivery switch means following the application of the pulse delivery control signal to the first pulse delivery switch means.