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Claims  |
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What is claimed is:
1. An automated external defibrillator, comprising:
a case;
a pair of defibrillator electrodes electrically connected to one another
within a package and including lead wires with connectors extending from
the package being removably disposed within the case;
electrode terminals being disposed within the case and configured for
electrical interconnection to the lead wire connectors of the
defibrillator electrodes;
a battery compartment and battery terminals in the case, the battery
compartment and terminals configured for holding and interconnecting to
one or more batteries;
a high voltage circuit being disposed within the case and coupled to the
battery terminals and the electrode terminals, for generating
defibrillation pulses and applying the pulses to the electrode terminals;
a maintenance indicator on the case; and
a digital control system being disposed within the case and coupled to the
electrode terminals, battery terminals, high voltage circuit and
maintenance indicator, and including self-test means for periodically and
automatically performing a self-test of the functionality of one or more
defibrillator components, and for actuating the maintenance indicator if a
malfunctioning component is identified wherein the self-test means
includes means for checking the defibrillator electrodes by providing
selected communications through a circuit formed in part of the lead wires
and the electrically connected pair of electrodes.
2. An automated external defibrillator configured for use with a packaged
pair of electrodes electrically connected to one another within the
package and including lead wires with connectors extending from the
package, the defibrillator including:
a case;
electrode terminals being disposed within the case and configured for
electrical interconnection to defibrillator electrode connectors;
a battery compartment and battery terminals in the case, the battery
compartment and terminals configured for holding and interconnecting to
one or more batteries;
a high voltage circuit being disposed within the case and coupled to the
battery terminals and the electrode terminals, for generating
defibrillation pulses and applying the pulses to the electrode terminals;
an impedance measuring circuit being disposed within the case for measuring
the impedance between the electrode terminals;
a battery level monitoring circuit being disposed within the case for
measuring the charge state of the batteries;
indicator on the case; and
a digital control system being disposed within the case and coupled to the
electrode terminals, battery terminals, high voltage circuit, impedance
measuring circuit, battery level monitoring circuit and maintenance
indicator, including:
self-test initiating means for periodically and automatically initiating
defibrillator self-tests, including daily self-test initiating means for
initiating a first set of self-tests at least once each day, and further
including weekly self-test initiating means for initiating a second set of
self-tests which is different than the first set of self-tests at least
once each week;
battery test means for checking the charge state of the batteries during
self-tests, and for actuating the maintenance indicator when low battery
charge states are identified;
electrode connection test means for checking the electrical interconnection
of electrodes to the electrode terminals as a function of the measured
impedance between the electrode terminals during self-tests, and for
actuating the maintenance indicator when disconnected electrode states are
identified;
high voltage circuit test means for checking the functionality of the high
voltage circuit during self tests, and for actuating the maintenance
indicator when high voltage circuit test faults are identified;
electronic memory;
memory test means for checking the functionality of the electronic memory
during self-tests, and for actuating the maintenance indicator when memory
faults are identified.
3. An automated external defibrillator configured for use with a packaged
pair of electrodes electrically connected to one another within the
package and including lead wires with connectors extending from the
package, the defibrillator including:
a case;
electrode terminals being disposed within the case and configured for
electrical interconnection to defibrillator electrode connectors;
a battery compartment and battery terminals in the case, the battery
compartment and terminals configured for holding and interconnecting to
one or more batteries;
a high voltage circuit being disposed within the case and coupled to the
battery terminals and the electrode terminals, for generating
defibrillation pulses and applying the pulses to the electrode terminals;
an impedance measuring circuit being disposed within the case for measuring
the impedance between the electrode terminals;
a battery level monitoring circuit being disposed within the case for
measuring the charge state of the batteries;
indicator on the case; and
a digital control system being disposed within the case and coupled to the
electrode terminals, battery terminals, high voltage circuit, impedance
measuring circuit, battery level monitoring circuit and maintenance
indicator, including:
self-test initiating means for periodically and automatically initiating
defibrillator self-tests;
battery test means for checking the charge state of the batteries during
self-tests, and for actuating the maintenance indicator when low battery
charge states are identified;
electrode connection test means for checking the electrical interconnection
of electrodes to the electrode terminals as a function of the measured
impedance between the electrode terminals during self-tests, and for
actuating the maintenance indicator when disconnected electrode states are
identified;
electronic memory; and
memory test means for checking the functionality of the electronic memory
during self-test, and for actuating the maintenance indicator when memory
faults are identified.
4. An automated external defibrillator, having a case and having
defibrillator components, including a packaged pair of defibrillator
electrodes electrically connected to one another within the package and
including lead wires with connectors extending from the package, at least
two electrode terminals configured for electrical interconnection to the
defibrillator electrodes, at least one self-contained power supply
disposed within the case, a high voltage circuit electrically coupled to
the at least one self-contained power supply and to the defibrillator
electrode terminals, the high voltage circuit for generating
defibrillation pulses and applying the pulses to the electrode terminals,
and a digital control system coupled to the electrode terminals, the at
least one self-contained power supply, and the high voltage circuit, and
including self-test means controlled by the digital control system for
periodically and automatically performing a self-test of one or more
defibrillator components, and for providing a maintenance indication if a
malfunctioning component is identified, the digital control system further
controlling a rescue mode of operation, the rescue mode of operation
including at least the steps of coupling the high voltage circuit to the
battery terminals and the defibrillator electrode terminals, generating
the defibrillation pulses, and applying the pulses to the defibrillator
electrode terminals, comprising:
a voice circuit operably coupled to the digital control system, and
a speaker operably coupled to the voice circuit,
whereby the digital control system provides commands to the voice circuit,
and responsive thereto, the voice circuit generates audible voice prompts
emitted by the speaker.
5. An automated external defibrillator, having a case and having
defibrillator components, including at least electrode terminals
configured for electrical interconnection to defibrillator electrodes, at
least one self-contained power supply disposed within the case, a high
voltage circuit electrically coupled to the at least one self-contained
power supply and to the electrode terminals, the high voltage circuit for
generating defibrillation pulses and applying the pulses to the electrode
terminals, and a digital control system coupled to the electrode
terminals, the at least one self-contained power supply, and the high
voltage circuit, and including self-test means controlled by the digital
control system for periodically and automatically performing a self-test
of one or more defibrillator components, and for providing a maintenance
indication if a malfunctioning component is identified, the digital
control system further controlling a rescue mode of operation, the rescue
mode of operation including at least the steps of coupling the high
voltage circuit to the battery terminals and the electrode terminals,
generating the defibrillation pulses, and applying the pulses to the
electrode terminals, comprising:
a real time clock being operably communicatively coupled to the digital
control system, the real time clock providing communication to the digital
control system enabling the digital control system to maintain track of
the steps of the rescue mode of operation.
6. An automated external defibrillator, having a case and having
defibrillator components, including at least electrode terminals
configured for electrical interconnection to defibrillator electrodes, at
least one self-contained power supply disposed within the case, a high
voltage circuit electrically coupled to the at least one self-contained
power supply and to the electrode terminals, the high voltage circuit for
generating defibrillation pulses and applying the pulses to the electrode
terminals, and a digital control system coupled to the electrode
terminals, the at least one self-contained power supply, and the high
voltage circuit, and including self-test means controlled by the digital
control System for periodically and automatically performing a self-test
of one or more defibrillator components, and for providing a maintenance
indication if a malfunctioning component is identified, the digital
control system further controlling a rescue mode of operation, the rescue
mode of operation including at least the steps of coupling the high
voltage circuit to the battery terminals and the electrode terminals,
generating the defibrillation pulses, and applying the pulses the
electrode terminals, comprising:
a real time clock being operably communicatively coupled to the digital
control system, the real time clock providing a signal of predetermined
magnitude to the defibrillator electrodes and receiving a return signal
therefrom, whereby the magnitude of the return signal from the
defibrillator electrodes is an indicator of the operability of the
defibrillator electrodes.
7. An automated external defibrillator, having a case and having
defibrillator components, including at least electrode terminals
configured for electrical interconnection to defibrillator electrodes, at
least one self-contained power supply disposed within the case, a high
voltage circuit electrically coupled to the at least one self-contained
power supply and to the electrode terminals, the high voltage circuit for
generating defibrillation pulses and applying the pulses to the electrode
terminals, and a digital control system coupled to the electrode
terminals, the at least one self-contained power supply, and the high
voltage circuit, and including self-test means controlled by the digital
control system for periodically and automatically performing a self-test
of one or more defibrillator components, and for providing a maintenance
indication if a malfunctioning component is identified, the digital
control system further controlling a rescue mode of operation, the rescue
mode of operation including at least the steps of coupling the high
voltage circuit to the battery terminals and the electrode terminals,
generating the defibrillation pulses, and applying the pulses to the
electrode terminals, comprising:
a real time clock being operably coupled to the digital control system, the
real time clock providing a real time basis for storing data related to
the time of placement of the defibrillator electrodes on the patient, the
initiation of a cardiac rhythm analysis voice prompt, the patient's
cardiac rhythm, the initiation of a charging voice prompt, the completion
of a charge mode of operation of the high voltage circuit, and the
initiation of a charge to the defibrillator electrodes.
8. An automated external defibrillator, having a case and having
defibrillator components, including at least two electrode terminals
configured for electrical interconnection to defibrillator electrodes, at
least one self-contained power supply disposed within the case, a high
voltage circuit electrically coupled to the at least one self-contained
power supply and to the electrode terminals, the high voltage circuit for
generating defibrillation pulses and applying the pulses to the electrode
terminals, and a digital control system coupled to the electrode
terminals, the at least one self-contained power supply, and the high
voltage circuit, and including self-test means controlled by the digital
control system for periodically and automatically performing a self-test
of one or more defibrillator components, and for providing a maintenance
indication if a malfunctioning component is identified, the digital
control system further controlling a rescue mode of operation, the rescue
mode of operation including at least the steps of coupling the high
voltage circuit to the battery terminals and the electrode terminals,
generating the defibrillation pulses, and applying the pulses to the
electrode terminals, comprising:
a voice circuit operably coupled to the digital control system, and
a speaker operably coupled to the voice circuit,
whereby the digital control system provides commands to the voice circuit,
and responsive thereto, the voice circuit generates audible voice prompts
emitted by the speaker, and
the rescue mode of operation including a selected sequence of steps to be
performed by an operator, the digital control system providing a series of
voice prompts to the operator to assist the operator in performing the
selected sequence of steps.
9. The defibrillator of claim 8 wherein the voice prompts at least include
prompts to the steps of directing the operator to properly place the
defibrillator electrodes on the patient, assess the cardiac rhythms of the
patient, and deliver the high voltage defibrillating charge to the
patient.
10. An automated external defibrillator configured for use with a packaged
pair of electrodes electrically connected to one another within the
package and including lead wires with connectors extending from the
package, the defibrillator including:
a case;
electrode terminals being disposed within the case and configured for
electrical interconnection to defibrillator electrode connectors;
a battery compartment and battery terminals in the case, the battery
compartment and terminals configured for holding and interconnecting to
one or more batteries;
a high voltage circuit being disposed within the case and coupled to the
battery terminals and the electrode terminals, for generating
defibrillation pulses and applying the pulses to the electrode terminals;
an impedance measuring circuit being disposed within the case for measuring
the impedance between the electrode terminals by providing selected
communications through a circuit formed in part of the lead wires and the
electrically connected pair of electrodes;
a battery level monitoring circuit being disposed within the case for
measuring the charge state of the batteries;
indicator on the case; and
a digital control system being disposed within the case and coupled to the
electrode terminals, battery terminals, high voltage circuit, impedance
measuring circuit, battery level monitoring circuit and maintenance
indicator, including:
self-test initiating means for periodically and automatically initiating
defibrillator self-tests;
battery test means for checking the charge state of the batteries during
self-tests, and for actuating the maintenance indicator when low battery
charge states are identified;
electrode connection test means for checking the electrical interconnection
of electrodes to the electrode terminals as a function of the measured
impedance between the electrode terminals during self-tests, and for
actuating the maintenance indicator when disconnected electrode states are
identified.
11. The defibrillator of claim 10 wherein the digital control system
further includes high voltage circuit test means for checking the
functionality of the high voltage circuit during self-tests, and for
actuating the maintenance indicator when high voltage circuit faults are
identified.
12. The defibrillator of claim 10 wherein the maintenance indicator
includes an audible indicator.
13. The defibrillator of claim 10 wherein the digital control system
further includes:
electronic memory; and
memory test means for checking the functionality of the electronic memory
during self-tests, and for actuating the maintenance indicator when memory
faults are identified.
14. The defibrillator of claim 13 wherein the self-test initiating means
includes daily self-test initiating means for initiating a first set of
self-tests at least once each day.
15. An automated external defibrillator, having a case and having
defibrillator components, including at least electrode terminals
configured for electrical interconnection to defibrillator electrodes, at
least one self-contained power supply disposed within the case, a high
voltage circuit electrically coupled to the at least one self-contained
power supply and to the electrode terminals, the high voltage circuit for
generating defibrillation pulses and applying the pulses to the electrode
terminals, and a digital control system coupled to the electrode
terminals, the at least one self-contained power supply, and the high
voltage circuit, and including self-test means controlled by the digital
control system for periodically and automatically performing a self-test
of one or more defibrillator components, and for providing a maintenance
indication if a malfunctioning component is identified, comprising:
the self-contained power supply having at least one primary battery for
powering the high voltage circuit and at least one backup battery.
16. The defibrillator of claim 15 wherein the at least one backup battery
comprises a battery rated at a lesser voltage than the at least one
primary battery.
17. The defibrillator of claim 15 wherein the at least one backup battery
comprises a battery rated at nine volts and the at least one primary
battery is rated at twelve volts.
18. The defibrillator of claim 15 wherein the digital control system
includes an operating program stored in a program memory, the operating
program utilizing the backup battery to perform self-tests when the
primary battery is determined to be in a low charge state.
19. The defibrillator of claim 15 wherein the self-test powered by the
backup battery provides a maintenance indication when the malfunctioning
primary battery is identified.
20. An automated external defibrillator, having a case and having
defibrillator components, including at least electrode terminals
configured for electrical interconnection to defibrillator electrodes, at
least one self-contained power supply disposed within the case, a high
voltage circuit electrically coupled to the at least one self-contained
power supply and to the electrode terminals, the high voltage circuit for
generating defibrillation pulses and applying the pulses to the electrode
terminals, and a digital control system coupled to the electrode
terminals, the at least one self-contained power supply, and the high
voltage circuit, and including self-test means controlled by the digital
control system for periodically and automatically performing a self-test
of one or more defibrillator components, and for providing a maintenance
indication if a malfunctioning component is identified, comprising:
the case having an openable and closeable lid, including means for
activating the self-test means when opening or closing said lid.
21. The defibrillator of claim 20 wherein the lid is communicatively
coupled to the digital control system, the means for activating the
self-test means including a means for communicating with the digital
control system which causes the digital control system to assess the
charge state of the at least one self-contained power supply and the
circuit integrity and the operability of the defibrillator electrodes when
the lid is opened or closed.
22. The defibrillator of claim 20 further including a switch operably
coupled to the case lid and operably communicatively coupled to the
digital control system, the switch providing a signal to the digital
control system representative of the open and closed conditions of the
case lid.
23. The defibrillator of claim 22 wherein the switch comprises a magnetic
reed relay switch.
24. The defibrillator of claim 22 wherein the digital control system
includes an operating program stored in a program memory, the operating
program controlling a rescue mode of operation, the rescue mode of
operation including at least the steps of coupling the high voltage
circuit to the battery terminals and the electrode terminals, generating
the defibrillation pulses, and applying the pulses to the electrode
terminals, the open signal of the lid switch acting to initiate the rescue
mode of operation.
25. The defibrillator of claim 24 wherein the lid is communicatively
coupled to the digital control system, the means for activating including
a means for communicating with the digital control system which causes the
digital control system to terminate the rescue mode of operation when the
lid is opened or closed. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to automated external
defibrillators. In particular, the present invention is an automated
external defibrillator with a self-test system for automatically and
periodically testing the operational status of the defibrillator, and for
providing service alerts if faults are identified.
2. Description of the Related Art
Automated external defibrillators or AEDs are used by police officers,
paramedics and other first-responder emergency medical technicians to
resuscitate cardiac arrest patients. It is important that the AEDs carried
by these technicians be continuously operational and ready for use on a
moments notice. To help ensure a high level of confidence that they will
be operational when needed, AEDs should be periodically checked and tested
by the technicians, and corrective maintenance performed if any faults are
identified. By way of example, AED functions and components that should be
periodically checked and tested include the charge state of the batteries,
the presence of electrodes and the ability of the device to charge and
deliver defibrillation pulses. The American Heart Association recommends
that AEDs be tested daily or at the beginning of a shift.
Unfortunately, for a variety of reasons the frequency at which AEDs are
tested by the technicians that will be using them varies. Since studies
have shown that the chances of successfully resuscitating a patient
decrease approximately ten percent per minute following cardiac arrest,
the consequences of first-responder medical technicians arriving at a
rescue location with a nonfunctional AED can be severe. There is,
therefore, a continuing need for AEDs capable of being reliably maintained
in a functional state.
SUMMARY OF THE INVENTION
The present invention is an improved automated external defibrillator
(AED). One embodiment of the defibrillator includes a digital control
system with self-test means for periodically and automatically performing
self-tests of one or more defibrillator components. If a malfunctioning
component is identified, the self-test means actuates an audible alarm or
other maintenance indicator to alert an operator. Tested functions include
the presence and interconnection of defibrillator electrodes, battery
charge state, the functionality of the high voltage circuit and the
functionality of the digital control system. Some functions are
self-tested daily, while others are self-tested weekly.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an automated external defibrillator (AED)
in accordance with the present invention, with the electrode compartment
lid closed.
FIG. 2 is a perspective view of the AED shown in FIG. 1, with the electrode
compartment lid opened and the packaged electrodes positioned therein.
FIG. 3 is a perspective view of the AED shown in FIG. 2, with the
electrodes removed from the electrode compartment and the package.
FIG. 4 is a detailed view of the diagnostic display panel in the electrode
compartment.
FIG. 5 is a detailed view of the unpackaged electrodes positioned on the
release liner.
FIG. 6 is a block diagram of the electrical system of the AED shown in FIG.
1.
FIG. 7 is an illustration of the instruction and safety label on the inside
surface of the electrode compartment lid.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A semi-automatic, automated external defibrillator (AED) 10 in accordance
with the present invention is illustrated generally in FIGS. 1-3. As
shown, defibrillator 10 includes a plastic case 12 with a carrying handle
14 on the top portion. A battery compartment (not visible) in the bottom
portion of the defibrillator 10 is enclosed by a semi-transparent battery
cover 16. An illuminatable rescue switch 18, visual maintenance indicator
20, data communication port 22 and charging port 24 are located on the
outside of case 12 for easy access by an operator.
Case 12 also includes an electrode compartment 26 between handle 14 and
battery cover 16. The electrode compartment 26 is enclosed by lid 28 which
is mounted to the case 12 by hinges (not visible). A friction-type
releasable latch including pins 30 holds lid 28 closed when defibrillator
10 is not in use. The finger-receiving recess 31 in the lid 28 is grasped
to open the lid and access the electrode compartment 26. An electrode
connector 32, speaker 34 and diagnostic display panel 36 are located on
case 12 within the electrode compartment 26. As shown in FIG. 4,
diagnostic display panel 36 includes visual "Call for Service" indicator
light 38, "Check Electrode" indicator light 40, "Check 9 Volt Battery"
indicator light 42, "Check 12 Volt Battery" indicator light 44 and "Power"
indicator light 46. Resume switch 48 and resume indicator light 49 are
also located on diagnostic panel 36. An instruction and safety label such
as that shown in FIG. 7 is located on the inside surface of electrode
compartment lid 28.
A pair of defibrillator electrodes 50 which can be used with defibrillator
10 are shown in FIGS. 3 and 5. Electrodes 50 each include a flexible
polymer backing layer 52 and a patient-engaging layer 54 of conductive
adhesive which overlays the backing layer. A current-dispersing flexible
conductive sheet (not visible) is located between the backing layer 52 and
patient-engaging layer 54. Insulated lead wires 56 extend from each
electrode 50, and have a first end connected to the conductive sheet and a
second end connected to connector 58. Connector 58 is configured to
releasably mate with the electrode connector 32 in electrode compartment
26. Electrodes 50 are sealed within a polymer or polymer-metal laminate
package 60 such as that shown in FIG. 2. Lead wires 56 and connector 58
extend from package 60. The layers 54 of electrodes 50 are affixed in a
face-to-face orientation to opposite sides of a release liner 61 within
package 60. The release liner 61 is perforated with a number of apertures,
so the electrodes 50 are electrically coupled to one another within the
package 60. A relatively low resistance electrical circuit is thereby
established between the ends of the lead wires 56 at connector 58. As
shown in FIG. 2, electrode package 60 is positioned within electrode
compartment 26, and connector 58 plugged into the connector 32 in the
compartment, to maintain defibrillator 10 in a ready-to-use state.
Packaged electrodes 50 having the above-described characteristics are
disclosed in the Gilman et al. U.S. Pat. No. 5,402,884, and are
commercially available from Survivalink of Minnetonka, Minn.
FIG. 6 is a block diagram of the electrical system 70 of defibrillator 10.
The overall operation of defibrillator 10 is controlled by a digital
microprocessor-based control system 72 which includes a processor 74
interfaced to program memory 76, data memory 77, event memory 78 and real
time clock 79. The operating program executed by processor 74 is stored in
program memory 76. Data memory 77 is used by processor 74 as a scratch pad
memory during the execution of the operating program. Electrical power is
provided by a rechargeable twelve volt lead-acid cartridge battery 80 and
a nine volt battery 82 which are removably positioned within the battery
compartment and connected to power generation circuit 84. During normal
operation, power generation circuit 84 generates regulated .+-.5 V, 3.3 V
and 12 V (actually about 13.3 V) supplies with the power provided by the
twelve volt battery 80. Nine volt battery 82 functions as a back-up
battery to power components of electrical system 70 during the execution
of self-tests and to activate maintenance indicators and alarms (as
described below) if the twelve volt battery 80 is low on charge. Although
not separately shown in FIG. 6, power generation circuit 84 includes
voltage level sensing circuits which are coupled to processor The voltage
level sensing circuits provide low battery level signals to processor 74
whenever the voltage levels of batteries 80 or 82 are less than
predetermined values such as 12.3 V and 8 V, respectively.
The .+-.5 V supply is used to power the control system 72 and most other
electrical components of electrical system 70. The 3.3 V supply is coupled
to nonvolatile event memory 78 in which, as is described in greater detail
below, data representative of the patient's cardiac rhythm and the rescue
mode operation of defibrillator 10 are stored. A high voltage generation
circuit 86 is connected to receive the 12 V supply. Charging port 24 is
coupled to power generation circuit 84, enabling twelve volt battery 80 to
be connected to a twelve volt vehicle battery (not shown) or a 120VAC
charger (also not shown) and recharged while mounted within the
defibrillator 12. Alternatively battery 80 can be removed from
defibrillator 10 and charged in a stand-alone charger (not shown).
Defibrillator 10 cannot be operated when a charger is connected to charge
port 24. Circuitry (not separately shown) within power generation circuit
84 senses the interconnection of port 24 to a charger, and provides a
charger connected signal to processor 74 when a connected charger is
sensed.
Power generation circuit 84 is also connected to power control circuit 88
and processor 74. Power control circuit 88 is connected to lid switch 90,
watch dog timer 92, real time clock 79 and processor 74. Lid switch 90 is
a magnetic reed relay switch in one embodiment, and provides signals to
processor 74 indicating whether lid 28 is open or closed. Data
communication port 22 is coupled to processor 74 for two-way serial data
transfer using an RS-232 protocol. Rescue switch 18, maintenance indicator
20, rescue switch light 19, resume switch 48, indicator lights 38, 40, 42,
44, 46 and 49 of diagnostic display panel 36, voice circuit 94 and
piezoelectric audible alarm 96 are also connected to processor 74. Voice
circuit 94 is connected to the speaker 34. In response to voice prompt
control signals from processor 74, circuit 94 and speaker 34 generate the
audible voice prompts described below.
High voltage generation circuit 86 is also connected to and controlled by
processor 74. Circuits such as 86 are generally known, and disclosed, for
example, in the commonly assigned Persson et al. U.S. Pat. No. 5,405,361,
which is hereby incorporated by reference. In response to charge control
signals provided by the processor 74, high voltage generation circuit 86
is operated in a charge mode during which one set of semiconductor
switches (not separately shown) cause a plurality of capacitors (also not
shown), to be charged in parallel to the 12 V potential supplied by power
generation circuit 84. Once charged, and in response to discharge control
signals provided by processor 74, high voltage generation circuit 86 is
operated in a discharge mode during which the capacitors are discharged in
series by another set of semiconductor switches (not separately shown) to
produce the high voltage defibrillation pulses. The defibrillation pulses
are applied to the patient through electrode connector 32 which is
connected to the high voltage generation circuit 86. Under certain
circumstances described below, processor 74 causes high voltage generation
circuit 86 to be discharged through an internal resistive load 98 rather
than connector 32.
Impedance measuring circuit 100 is connected to electrode connector 32 and
real time clock 79, and is interfaced to processor 74 through
analog-to-digital (A/D) converter 102. The impedance measuring circuit 100
receives a clock signal having a predetermined magnitude from clock 79,
and applies the signal to electrodes 50 through connector 32. The
magnitude of the clock signal received back from the electrodes 50 through
connector 32 is monitored by impedance measuring circuit 100. An impedance
signal representative of the impedance present across electrode connector
32 is then generated by circuit 100 as a function of the ratio of the
magnitudes of the applied and received clock signals (i.e., the
attenuation of the applied signal). For example | | |
