US3442269A - Defibrillator and control circuit - Google Patents

Description

United States Patent 3,442,269 DEFIBRILLATOR AND CONTROL CIRCUIT Walter S. Druz, Oakbrook, Ill., assignor to Zenith Radio Corporation, Chicago, Ill., a corporation of Delaware Filed Dec. 20, 1965, Ser. No. 515,018 Int. Cl. A61b 19/00 US. Cl. 128-419 6 Claims ABSTRACT OF THE DISCLOSURE There is described control circuitry for use in a defibrillator-cardioscope unit which circuitry displays substantial patient and equipment protective features. Specifically, means are provided for triggering the defibrillator with a synchronizing signal developed from and in a predetermined phase relation to the patients heart beat to deliver a single defibrillation impulse to the patient and for coincidentally inhibiting further effective operation of the triggering signal source. There is also provided a selector switch having a plurality of control positions for variously interrelating the operation of the defibrillator and the cardioscope to provide safe, simplified operation of the combined unit.

Specification The present invention relates to a defibrillator-cardioscope unit and, more particularly, to control circuitry displaying substantial patient and equipment protective features for use therein.

A defibrillator is a well-known medical electronic device useful in terminating fibrillation of the heart, that is, an uncontrolled or arhythmic expansion and contraction of various groups of heart muscles. This state may be induced by accidental electric shock or by severe stress as in the case of surgical operations, heart attacks, drownings or the like. When encountered, prompt and effective counter-measure must be taken if the patient is to survive. It is well-known that defibrillation, or reinstitution of rhythmic muscle operation in the heart, may be achieved by the application of a controlled electric shock thereto and a number of devices for this purpose have been proposed.

One device which has proven particularly well suited to this end in extensive clinical testing, and which is further adapted for portable emergency on-the-site use is illustrated and claimed in a copending application of Walter S. Druz, Ser. No. 291,703, filed July 1, 1963, now Patent No. 3,258,013, and assigned to the same assignee as the present invention. In the Druz application, there is shown an electronic defibrillator energized from a wholly self-contained battery power supply and comprising an inverter and a full-wave rectifier for converting low voltage battery energy to high voltage energy which is stored in a delay line pulsing circuit. The delay line circuit includes a plurality of capacitors for storing a predetermined electrical charge and inductive means for appropriate shaping of the waveform on discharge. In operation, the delay line is charged over a predetermined period of time to accumulate the necessary energy and then discharged over a relatively short time interval through a pair of electrodes placed at spaced locations on opposite sides of the patients heart.

For various reasons, it has been found desirable to associate in the same enclosure with the defibrillator a cardioscope and to interrelate in certain respects operaice tion of these devices. For instance, it is often desirable to visually monitor the patients heart beat before and after defibrillation. In certain cases of mild arhythmia of the heart such as in atrial fibrillation, i.e., a condition in which the atrial chambers of the heart beat at a rate different from that of the ventricles, the patient is not in mortal danger but to restore the heart to proper efiicient operation it is believed by many to be necessary to apply the defibrillation impulse in a predetermined time relation with the heart beat to avoid possible institution of severe fibrillation. Also, in correlating the equipment in these respects, it is essential, for obvious reasons, to avoid unduly complicating operation of the device for the technician and it is highly desirable to incorporate inherent patient and equipment safety features.

It is therefore an object of the present invention to provide control circuitry for operatively interrelating, in a predetermined fashion, a defibrillator and cardioscope.

It is a further object of the present invention to provide an improved defibrillator-cardioscope unit displaying significant patient and equipment safety features.

It is another object of the present invention to provide a control mechanism for correlating operation of a defibrillator and cardioscope which is relatively simple for the average technician to operate, even under the stress of an emergency.

In accordance with the invention, there is provided an electronic defibrillator-cardioscope, operable from a direct current energy source, which comprises first capacitor means for toring high voltage electrical energy supplied from a direct current source, a pair of defibrillator electrodes and switch means normally coupling the first capacitor means to the direct current source but actuable to couple the first capacitor means to the electrodes. The cardioscope portion of the system includes a cardiac signal amplifier for developing an amplified output of the beat of a patients heart and a synchronizing signal amplifier, coupled to the cardiac amplifier, for developing triggering signals in a predetermined phase relation to the beat of the patients heart. Control circuitry is provided in the form of actuating means, coupled to the synchronizing signal amplifier, and responsive to a triggering signal for operating the switch means and inhibiting means, responsive to the actuation of the switch means by the actuating means, for preventing further effective operation of the synchronizing signal amplifier.

In accordance with further aspects of the invention, there is provided a selector switch having a plurality of control positions for variously interrelating operation of the defibrillator and cardiscope, and apparatus for providing safe, simplified operation of the combined unit.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, the single figure of which is a schematic circuit diagram of a preferred embodiment of the defibrillator-cardioscope unit of the invention.

Referring now to the figure, there is shown in the upper left-hand portion of the drawing a portable battery operated defibrillator and in the upper right-hand portion of the drawing a cardioscope, these units being intercoupled in accordance with the invention by a four position selector switch (lower right-hand portion of drawing) and a control circuit shown within dashed outline 10.

More particularly, the illustrated defibrillator comprises an inverter 11 energized from a self-contained battery supply 12 through the closed contacts of an onoff switch 13. Switch 13, illustrated in its on position, is operated by a control knob 15 preferably located on the front control panel of the defibrillator-cardioscope en closure. Inverter 11 is also provided with an output to the primary of a step-up transformer lfi, the secondary winding of transformer E being coupled to a full-wave rectifier 17. Rectifier 17 is in turn normally coupled to an energy storage means 18 through a fixed contact 20 and a movable armature 21 of a switch means or relay 22 having its energizing coil 82 within control circuit 10. Preferably energy storage means 18 constitutes a delay line discharge pulsing circuit having first capacitor means for storing high voltage electrical energy and a plurality of inductors for appropriately shaping the discharge waveform from the storage capacitors. A pair of electrodes 23 and 24 are coupled respectively to a grounded output terminal 25 of delay line 18 and a fixed contact 27 of relay 22. The electrodes are adapted to be applied to the body of a patient at spaced locations on opposite sides of the heart during operation of the defibrillator. In the mode of operation of the defibrillator independent of the cardioscope portion of the unit, relay 22 is operated, to displace movable armature 21 to fixed contact 27 and apply the stored defibrillation energy across the electrodes, by closure of a pair of series connected normally open switches 29 and 30, the actuating members of which are conveniently positioned in the respective insulative handles of the electrodes 23 and 24, as schematically indicated by the dotted lines in the drawing.

The defibrillator also preferably includes a transistorized sensing circuit 32 having an input taken across output terminals 25 and 26 of delay line 18 and an output from a lead 33 to control circuit 10. As will be explained more fully hereinafter, sensing circuit 32 monitors the voltage across the output terminals of delay line 18 and develops a control signal to operate a relay, having an energizing coil 59 Within control circuit and a contact pair 35 coupled to inverter 11, for alternately enabling and disabling inverter 11 to maintain the charge stored in delay line 18 at a preselected value over a prolonged time interval.

The structural details of inverter 11, rectifier 17, delay line 18 and sensing circuit 32 are not illustrated as they are not of essential moment to the subject invention and for present purposes may be of any suitable, known construction. However, a preferred embodiment of these circuits for providing a defibrillation waveform of a unique and highly effective duration, energy content and waveshape is disclosed and claimed in the aforementioned Druz application.

The cardioscope portion of the unit comprises a cardiac signal amplifier 37 having an input from leads 39 and 40 which are coupled to electrodes positioned on opposite sides of the patients heart. For instance, one electrode may be applied to the left ankle of the patient while the other is applied to his right wrist. Amplifier 37 develops a balanced output with respect to a ground or reference potential which output is applied to the vertical deflection plates of a cathode ray tube display system Q. The horizontal deflection plates of the cathode ray tube are provided with a relatively low frequency scanning voltage from a horizontal sweep circuit 42. Details of circuit 42 and the electron beam focusing, intensity control apparatus, etc. for oscilloscope 4 1 are not shown for the sake of simplicity, but it is understood that this apparatus may be of conventional, known construction.

One terminal of cardiac amplifier 37 also provides an input for a synchronizing signal amplifier, indicated generally within the dashed outline 44 of the drawing. Amplifier 44 includes a diode 46 for clipping the peak portion of the cardiac signal and substantially conventional transistor amplifying circuitry including -NPN amplifier transistors 48 and 112, the latter being coupled to an NPN emitter follower output transistor Q. The collector electrode of transistor 4 9 is returned as an input to cardiac signal amplifier 37 through a diode 51 to permit, under proper circumstances, display of the synchronizing signal conjointly with the cardiac signal on the screen of oscilloscope 4 1.

The defibrillator is controlled and the operation of the cardioscope and defibrillator are interrelated by control circuit 10 and a four position function selector switch. The selector switch is shown in the drawing to comprise a pair of wafer sections 53 and 54, respectively designated as the function selector wafer and the power control wafer, ganged on 'a common control shaft for operation from a single control knob 56 located on t he front control panel of the defibrillator-cardioscope enclosure. Each wafer is conventional in construction having a fixed outer segment with contact points spaced about its periphery and a movable inner segment, usually referred to as a rotor, carrying one or more contact segments, as shown.

Specifically, control circuit 10 comprises a NPN transistor ii having an input to its base electrode from lead 33 of voltage sensing circuit 32. The collector electrode of transistor includes the parallel combination of a capacitor 60 and a relay energizing coil 59 for operating contact pair 35, as indicated in the drawing by the dashed line joining contacts 35 and coil 59. The remaining terminal of coil 59 is returned to battery power supply 12 through a fixed contact 61 and a movable relay armature 62, normally positioned to engage contact 61. The emitter electrode of transistor Q is directly coupled to the collector electrode of a normally non-conductive PNP transistor 6 5 which in turn has its emitter electrode returned to battery 12 through a diode 64 coupled in series with the emitter-base junction of transistor 65 and poled in the same direction as this junction. A voltage dividing network comprising series connected resistors 66 and 67, having their common junction coupled to the base of transistor Q, is connected from battery supply 12 through a contact segment shunting adjacent contact points 68 and 69 of wafer switch 53 and through series electrode switches 29 and 30 to ground or a source of reference potential. Concurrent closure of switches 29 and 30 to apply a ground at one terminal of resistor 67 develops a bias potential at the base of transistor Q suflicient to render it conductive. Transistor 5 has an additional input to its base electrode through a resistor 70 coupled to the collector electrode of a normally nonconductive transistor switch E. The base electrode of transistor 2 is coupled to its grounded emitter electrode through a resistor 72 and to a contact point 74 on wafer switch 53 through a series resistor-capacitor network 76, 77.

The collector electrode of transistor in addition to being coupled to the emitter electrode of transistor g, is also coupled to ground through the parallel combination of a capacitor 79, a transient suppressing diode and an energizing coil 82 adapted to operate movable armature 21 of relay 22, as shown schematically in the drawing by the dashed line joining these elements. The collector of transistor 5 is coupled to further circuitry through the anode of diode 84. Specifically the cathode of diode 84 is coupled to the collector electrode of transistor 48 of synchronizing signal amplifier 44 by a capacitor 85 shunted to ground and a diode 86, poled to conduct with diode 84. The cathode of diode 84 is also coupled to a fixed relay contact 88 through a resistor 89 and to a contact point 91 on wafer switch 53 through the parallel combination of capacitor 93 an an energizing coil 94 for movable armature 62. An adjacent contact point 95 on wafer 53 is grounded.

The cardioscope portion of the combined unit is ikewise coupled to a plurality of contact points on wafers 53 and 54 of the function Selector switch. Specifically, horizontal sweep circuit 42 and cardiac signal amplifier 37 are coupled to a contact point 96 of power supply wafer 54 while synchronizing signal amplifier 44 is coupled to an adjacent contact point 97 thereon. A contact point 98 of wafer 54 is coupled to the positive terminal of battery 12. A signal output of sync amplifier 44, taken at the mid-point of a voltage dividing network 99 coupled to the emitter electrode of transistor Q, is connected to a contact point 100 of wafer 53. Contact point 100 is also coupled to ground through a normally closed contact of a manually operated switch 101, located on the front control panel of the defibrillator-cardioscope unit, to effectively suppress the sync signal output.

In explaining the operation of the circuit of the invention, it will initially be assumed that the defibrillator portion of the combined unit is in an on condition with the delay line undergoing charging and that the cardioscope is in an off condition. Thus, switch 13 is closed and control knob 56 is in its off position both as illustrated in the drawing and the various relays and switches are also in the positions depicted in the drawing. In this condition, direct current from battery 12 energizes a transistorized square-wave oscillator within inverter 11 to generate an alternating current voltage of square or rectangular waveform at a frequency of about 800 cycles per second. This voltage is amplified within inverter 11 by a push-pull power amplifier and the amplified alternating voltage output is stepped-up to a higher voltage by stepup transformer 1 (i and impressed on full-wave bridge rectifier 17 to supply direct current at a higher voltage than that of battery 12. This output from the high voltage direct current source comprising battery 12, inverter 11 and rectifier 17 is employed to charge the storage condensers of delay line 18 to a voltage which may exceed 3200 volts.

Transistorized sensing circuit 32 meters the voltage across the output terminals of delay line 18 and applies a control signal at the base of transistor Q. Conduction of transistor energizes relay coil 59 and operates its contacts 35 thereby alternately enabling and disabling operation of the inverter to maintain the voltage of the delay line at a constant preselected value over a long period of time despite leakage currents, etc. As taught in the aforementioned Druz application, closure of relay contacts 35 removes a reverse bias on the power amplifier transistors within unit 11 and permits them to operate in conventional fashion; however, any use of relay contacts 35 to permit inhibiting of the operation of the inverter is satisfactory for purposes of the present disclosure and accordingly the circuit is not illustrated in detail.

In closed chest utilization of the defibrillator, electrode 23 is placed on the right border of the sternum just below the sternal notch while electrode 24 is placed on the mid-clavicular line near the fifth interspace, with the heart approximately midway between. For internal use, following thoracectomy, the electrodes may be applied directly across the heart itself. Upon ascertaining that the energy stored in the delay line is at the requisite level determined by the attending physician, switches 29 and 30, located within the respective handles of electrodes 24 and 23, are closed to apply a ground potential through contact points 69 and 68 of wafer 53 to one terminal of resistor 67. The resultant decrease in base voltage of transistor tfi renders it conductive and applies essentially the battery 12 voltage across energizing coil 82 to displace its armature 21 to fixed contact 27 and discharge the energy stored within the delay line through the electrodes and the heart of the patient to accomplish defibrillation. Conduction of transistor {i5 als applies battery potential to the emitter electrode of transistor Q thereby inhibiting effective operation of the sensing circuit 32 to operate inverter 11 during the interval of defibrillation. It has been found that if inverter 11 is permitted to operate during this period, the resultant high open circuit voltage developed within the power amplifier and across rectifier bridge 17 might severely damage this apparatus. The circuit just described inherently inhibits such from occurring if coil 82 is energized to operate the defibrillator and thus provides an important and fail-safe equipment protection feature. Upon termination of the defibrillating impulse, the handle switches in electrodes 23 and 24 are released to restore the apparatus to its normal charging condition.

When the function selector control knob 56 is moved to its on position indicated in the drawing, the contact portion of wafer 54 is oriented to electrically couple contact points 98 and 96 to apply an operating potential to cardiac signal amplifier 37 and horizontal sweep circuit 42 and, although not shown in the drawing in the interest of simplicity, power is also applied to the electron gun structure of oscilloscope Q. With electrocardiograph electrodes 39 and 40 properly positioned in spaced locations on opposite sides of the patients heart, as hereinbefore described, a visual display of the electrical activity of a patients heart is provided on the screen of the oscilloscope. The operation of the defibrillator is still identical to that previously described and there is no interrelation of the operation of the defibrillator and cardioscope in this function position. In fact, control knob 15 of the defibrillator may be manipulated to remove power from the defibrillator without in any respect hindering operation of the cardioscope. Thus, the units may be operated totally independently of one another, and are provided with separate operating controls for this purpose in the interest of simplicity and safety.

With the function control knob 56 rotated to the position designated sync in the drawing, the single contact strip on wafer 54 electrically couples contact points 96, 97 and 98, thus also supplying power to synchronizing signal amplifier 44. The contact section of wafer 53 previously connecting contacts 68 and 69 is rotated clear of these points thereby rendering defibrillator handle switches 29 and 30 ineffective. No other electrical contacts are made. In the sync position, operation is again identical to that described for the on position excepting only that synchronizing signal amplifier 44 is rendered operative and that the defibrillator can no longer be operated. Thus, the peak portion of the cardiac signal is clipped by diode 46, amplified by transistors :18 and 12 and applied as an additional input to cardiac signal amplifier 37 through a diode 51. Thus synchronizing pulse appears as a sharp spike on the R wave of the ECG waveform on the display screen of oscilloscope 51. Preferably the synchronizing signal pulse is phased with respect to the beat of the patients heart such as to occur either on the peak or trailing portion of the QRS complex of the electrocardiograph. The synchronizing pulse also would be developed at the midpoint of voltage divider .99 of the sync amplifier except for the ground potential applied to this .point through normally closed, manually operated switch 101. The synchronizing signal is ultimately calculated to trigger operation of the defibrillator in a timed relation to the patients heart beat, but for reasons of safety the sync position is provided to permit the technician to clearly establish that the synchronizing signal amplifier is working properly before coupling to the defibrillator.

Movement of the function control knob 56 to the convert position maintains the same electrical contacts on wafer 54 as previously described for the sync position; however, on Wafer 53, contact point 91 and grounded contact point are coupled by one contact segment while contact points 74 and are joined by a second segment. Thus, a ground is applied at one terminal of energizing coil 94 and a conductive connection is made from the midpoint of a voltage divider network 99 to the base electrode of normally non-conductive transistor switch 11. However, the synchronizing signals are still not effective to operate transistor 7 1 because of the ground shunt for these signals provided by switch 101.

Once the attending physician has determined that all is in order, the patients heart arhythmia may be electrically converted by depression of manually operated switch 101 to permit application of the next succeeding synchronizing signal pulse to the base of transistor 21 through coupling network 76, 77. This action renders transistor 3 conductive and transistor Qi is in turn rendered conductive to develop substantially the battery supply voltage at its collector electrode. Thus, coil 82 of relay 22 is energized to permit discharge of the energy stored within delay line 18 through defibrillator electrodes 23 and 24 and the patient, while transistor is inhibited from further effective operation, all as previously discussed. Also, because of the ground at contact point 91, coil 94 is energized from the battery supply potential at the collector of transistor Q and moves its associated armature 62 to fixed contact 88 thereby concurrently establishing a holding circuit for it self and applying a forward bias to diode 86. Forward biasing of diode 86 couples signal shunting capacitor 85 to the collector electrode of transistor 4 8 of sync amplifier 44 to inhibit further effective operation of the synchronizing signal amplifier. Since contact 62 is disengaged from contact 61, relay 59 cannot be energized and contacts 35 remain open, thereby preventing the delay line from recharging.

Diode 84 prevents application of the holding circuit potential to coil 82 and to the emitter of transistor Q. Thus, transistor 8 and coil 82 are restored to their normal condition after a time interval determined by the duration of the sync inpulse and the time constant of the associated control circuitry. However, the previously described holding circuit continues to preclude further effective operation of the synchronizing signal amplifier 44 and this amplifier can only be restored to its prior operative condition by manipulating control knob 56 back to the sync position. This is an important safety feature as successive coupling of the delay line to the patient would discharge energy from a partially charged delay line through the patient with the possible result of reinstituting fibrillation in the heart. Also, for safety, switch 101 is physically separated from the function selector switch and is also preferably seated in a shallow well on the front control panel of the unit to avoid accidental operation. Thus, there has been shown new and unique control circuitry for interrelating the operation of the cardioscope and defibrillator in a manner that provides for simplified operation by a technician, as is essential in emergency circumstances, and also provides maximum patient and equipment protective features which are operative substantially independent of the care or skill of the operator.

While a particular embodiment of the invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made Without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. An electronic defibrillator operable from a direct current energy source comprising:

first capacitor means for storing high voltage electrical energy supplied from said direct current source;

a. pair of defibrillator electrodes;

switch means normally coupling said first capacitor means to said direct current source but operable to couple said first capacitor means to said electrodes;

a cardiac signal amplifier having an input circuit adapted to be coupled to a patient for developing an amplified output of electrical activity of the beat of the patients heart;

a synchronizing signal amplifier having an input circuit coupled to said cardiac amplifier and having an output circuit, for developing triggering signals in a predetermined phase relation to the beats of the patients heart;

a manually operable control switch in said output circuit of said synchronizing signal amplifier;

actuating means coupled to said output circuit and responsive to a predetermined one of said triggering signals following operation of said control switch for operating said switch means to deliver a single defibrillatory impulse to the patient;

inhibiting means including a circuit coupled to said control switch and responsive to said predetermined triggering signal for disabling said synchronizing signal amplifier and preventing reactuation of said switch means, whereby the patient is protected against undesired application of additional defibrillatory impulses;

and reset means operable to release said inhibiting means. 2. The combination according to claim 1 and further comprising manually controlled means normally precluding response of said actuating means to said triggering signals but operable to permit response of said actuating means thereto, and wherein said inhibiting means includes a triggering signal bypass capacitor, a diode, and means for forward-biasing said diode during operation of said inhibiting means to couple said triggering signal bypass capacitor to said synchronizing signal amplifier.

3. The combination according to claim 1 and further comprising a cathode ray tube display system having one display axis coupled to both said cardiac signal amplifier and said synchronizing signal amplifier for providing a visual display of the electrical activity of the beats of the patients heart and the phase relation of said triggering signals thereto.

4. The combination according to claim 3 and further comprising a defibrillator-cardioscope selector switch having one operating position for coupling said amplifiers only to said cathode ray tube display system and a second operating position for in addition coupling said synchronizing signal amplifier to said actuating means, and means including a manually operable switch for normally preventing response of said actuating means to said triggering signals but operable to permit response thereto. 5. In an electronic defibrillator of the type employing first capacitor means for storing high voltage electrical energy supplied from a direct current energy source and a pair of electrodes for discharging said stored energy through a patient, the improvement comprising:

sensing and control circuit means, including a first transistor switch having emitter, base and collector electrodes, a relay having contacts coupled to said energy source and having an energizing coil coupled to said collector electrode and operative upon conduction of said first transistor switch, and voltage sensing apparatus coupled between said first capacitor means and said base electrode to apply a signal to said base electrode related to the voltage across said first capacitor means, for alternately enabling and disabling said direct current source in response to the value of the voltage across said first capacitor means for maintaining the energy stored in said first capacitor means at a preselected level; switch means normally coupling said first capacitor means to said direct current energy source but actuable to couple said first capacitor means to said pair of electrodes;

and actuating means, including a second transistor switch, for applying a signal of a predetermined potential to both said emitter electrode of said first transistor and to said switch means for concurrently inhibiting operation of said first transistor switch and for actuating said switch means.

6. The combination according to claim 5 and further comprising a cardiac signal amplifier having an input circuit adapted to be coupled to a patient for developing an amplified output of the electrical activity of the beats of the patients heart, a synchronizing signal amplifier coupled to said cardiac amplifier for developing triggering signals bearing a predetermined phase relation to the beats of the patients heart, means for applying a triggering signal to said actuating means for operating said actuating means, and inhibiting means coupled to said actuating means and responsive to said predetermined potential upon operation of said actuating means for 10 preventing further effective operation of said synchronizing signal amplifier.

References Cited UNITED STATES PATENTS 3,236,239 2/1966 Berkovits 128-419 WILLIAM E. KAMM, Primary Examiner.

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