US3513850A - Direct current defibrillator with voltage-controlling means - Google Patents

Description

P. WEBER May 26, 1970 DIRECT CURRENT DEF'IBRILLATOR WITH VOLTAGE-CONTROLLING MEANS Filed July 25, 1967 SMN www

QRN I United States Patent O H Int. Cl. A6111 J/ U.S. Cl. 12S-421 6 Claims ABSTRACT OF THE DISCLOSURE A defibrillator that is useful for the treatment of certain heart disorders by the application of an electric shock voltage to the heart comprising circuitry which ensures that, while a shock voltage is being applied to the patient, the storage capacitors, whose discharge provides the shock voltage, are not simultaneously being charged. A control is provided which enables increasing or decreasing the shock voltage, if required, just before releasing it. Furthermore, the charged capacitors are automatically discharged across discharge resistors when the equipment is shut off, guaranteeing that a shock voltage cannot be accidentally applied to a patient, as soon as the equipment is reenergized and before he is ready for receiving the shock voltage. The shock voltages can be applied, by further improvements in circuitry, either asynchronously or synchronously with the heart beat.

BACKGROUND OF THE INVENTION This invention relates to direct current defibrillators, which are medical instruments for treating the human or animal heart by the application of an electric voltage shock to the heart. The dangerous condition of the heart wherein the heart muscle fibers are quivering or tremoring independently and without rhythm, in what is called the brillating state, can be arrested by this means, and the heart can fbe resuscitated and restored to its normal activity.

The electrical voltage shocks are generally applied by body electrodes, either arranged externally at the chest or internally, directly at the wall of the heart. It has been determined that voltages of from one to seven kilovolts may be applied for such an electric shock. These shock voltages can, moreover, be released either in a non-synchronized manner at any desired moment, or in a synchronized manner, that is, controlled by phases of the heart activity. In the ltater case, it is necessary to pick up the natural heart activity voltages in a manner known from the techniques of electrocardiographs, and to use a certain phase, especially the peak of the so-called R-phase of the heart voltage, to trigger the release of the electric shock voltage.

SUMMARY OF THE INVENTION The basic concepts of this invention arose from the perception that certain safety precautions used until now in connection with equipment for producing electric shocks become unnecessary if certain improvements are incorporated in the defibrillators. Namely, one especial l danger to the patients derives from the circumstance that 'ice the physician may find a suitable moment for releasing the shock voltage. During this time, the high voltage produced by the capacitor charge is an ever-present danger to the patient as well as to the attending physician. Therefore one of the aims of this invention is, essentially, to shorten the time duration when the storage capacitor is fully charged.

This problem of personnel safety is solved by means of the improvements of direct current defibrillators according to the invention. The invention features a separating control, including a switch inserted in the alternating (AC) voltage path for the capacitor charging, and a releasing control, including a switch for releasing the shock voltage into the shock transferring line. The separating control ensures that the capacitor is not being charged simultaneously with the application of a shock voltage to the patient. The releasing control determines the instants at which the shock voltages are applied to the patient. It should `be pointed out at this time that only a few, perhaps even only one, shock pulses are administered at any one treatment.

These two controls are actuated essentially in a synchronized manner but in a contrary sense. The contrary sense refers to the fact that when the switch associated with the releasing control is closed, the switch associated with the other control is opened, and vice versa, and both switches are coupled with a voltage-controlling device for the storage capacitor.

The first embodiment for making defbrillators more safe involves the release of a shock voltage not controlled by or synchronized with a phase of the heart activity voltage. lf synchronization is required, which involves a second embodiment, the releasing switch will not be actuated unconditionally synchronously with the separating switch, in a contrary sense, but conditionally, depending upon the arrival of a pulse of the heart activity voltage, t0 which pulse the shock is to be synchronized.

BRIEF DESCRIPTION OF THE DRAWING For a complete understanding of the invention, together with other objects and advantages thereof, reference may be had to the figure, showing the circuit diagram for the essential components of a defibrillator constructed according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An alternating current (AC) power supply is connected to two fixed contacts of normally-open switch 2. The other two fixed contacts of switch 2 are connected, through arms 4a and 4b of double-pole double-throw switch 4, to leads 1a and 1b connected toy variable transformer 30.

The function of switch 4, which is a part of relay 7, and is controlled by relay coil 7a, will be described in more detail below.

The supply control 2c connects and disconnects both the alternating (AC) supply 32 and the direct current (DC) supply 36. Supply control 2c also controls switch 47, whose function will be described in more detail below.

A potentiometer having a tap with a variable position could be used instead of the variable transformer 30. Line 1c connected to transformer tap 31 and line 1b are connected across the terminals of a high voltage transformer 3, the primary winding of which is indicated by 3P and the secondary winding by 3S. Connected to this secondary winding 3S is a conventional voltage doubler circuit, including the rectifiers D1 and D2 and the storage capacitors C1 and C2.

Because the rectifier circuit is the conventional voltage doubler circuit, using both half-waves of the alternating voltage, it permits charging the storage capacitors C1 and C2 more quickly. This manner of wiring also prevents superimposed magnetization of the secondary Winding 3S of the transformers 3` by direct current; moreover, the transformer then requires only half the number of windings that is required when using a single-wave rectifier. The dielectric strength requirements for the transformer 3, therefore, can also be reduced.

Awoltage divider network connected to the charge storage lines 18a and 18h serves to control the rate of charge of the storage capacitors C1 and C2. The network consists essentially of the following: a voltage divider fixed resistor R1 connected to the junction of ignition capacitor 23, the tap 34 of variable resistor R2, and one lead 22a connected to a glow discharge tube 25. The other terminals of ignition capacitor 23, variable resistor R2, and glow discharge tube 25 are also connected to a common terminal point on lead 18b.

Line 22a contains, instead of the usual indicating device, such as a voltmeter, a glow discharge tube 25, which initates pulses which result in triggering pulses being sent along the two pairs of controlling lines 9 and 10. These pulses then actuate the separating switch 4 of the power supply lines. Between the controlling lines 9 and 10 is located a pulse amplifier 8, whose function will be fully described herein below.

In line 22b and across the tapped resistance of variable resistor R2 is the ignition capacitor 23. This capacitor 23 serves to produce a strong ignition current pulse, if its voltage due to the charge on its plates exceeds the breakdown voltage of the glow discharge tube 25. It is well known that a glow discharge tube is switched into its conducting state at a certain fixed voltage, the socalled ignition or break-down voltage. Therefore, it is necessary to adjust the partition of the voltage divider network in a manner corresponding to the desired relation between the value of this breakdown voltage and the amplitude of the desired electric shock voltage.

The first ignition spark, produced in the glow discharge tube 25 when the breakdown voltage is reached, causes a triggering pulse across the resistance of photoelectric device 11, which is conducted by lines 9 and 10 to pulse amplifier 8. Pulse amplifier 8 is supplied with direct current by DC power supply 36 through leads 8a and switch contacts 48a and 48-b controlled by supply control 2c. The amplified current pulse at the output of pulse amplifier 8 and flowing through the coil 7a of an auxiliary relay switch 7 causes the movable arms 4a and 4b of switch 4 to move to their downward attracted position (the position other than that shown in the figure). This interrupts the charging of the storage capacitors C1 and C2 during this time by interrupting the flow of current through lines 1a and 1b and the primary winding 3P of transformer 3.

Included in the block labelled pulse amplifier 8 is switching circuitry (not shown in the figure, but including, for example, a multivibrator), such that, after having been triggered once by glow discharge tube 25, pulse amplifier 8 feeds current through the coil 7a of relay 7, as long as switch arms 48a and 48b of switch 48 are in their downward position, i.e. as long as the supply control 2c is in its downward position. Thus, if it is desired to send another pulse through the patient, supply control 2c must first be actuated, and the alternating current (AC) power temporarily interrupted.

Connected across the voltage divider net-work are the leads 18a and 18b, which are each connected to a fixed contact of a switch 270, which is a part of relay 27. Connected across the two other fixed contacts of switch 270 is the application circuit, including leads 17a and 17b and the two application electrodes 29a and 29b. The electrodes are joined to the body of the patient 33 in proximity to the heart or internally directly at the heart, thus the application circuit is completed by the body or by the heart of the patient. Generally, the application circuit also includes a choke impedance coil 28 which damps the rise of the current pulse when the shock voltage is released for application. Experience has shown that inclusion of choke coil 28 results in a more efiicacious shock voltage waveform.

It will be observed that, after the storage capacitors C1 and C2 have been fully charged, a shock voltage pulse cannot be transmitted to the patient until the alternating current shock relay coil 12 has been energized. This shock relay 12 is energized either synchronously or asynchronously, depending upon the purpose, and under the control, of the attending physician. For asynchronous operation, the arms of switches 38 and 13 would be in positions other than those shown in the figure, while switch arm 45aof switch 45 would be in the position shown. For synchronous operation, the arms of switches 38 and 13 would be in the positions shown in the figure, while switch arm 45a of switch 45 would be in a position alternate to that shown in the figure.

Two alternative embodiments are shown in the figure. The first embodiment, which involves release of the shock voltage without regard to synchronization lwith the heart beat, will occur with arm 13a of switch 13 in the position alternate to that shown in the figure. The invention contains as an essential part a controlling circuit energized through lines 5. Alternating current (AC) power from AC supply 32 is supplied to lines 5 through the separating switch 4 when it arms 4a and 4b are in positions alternate to those shown in the figure, that is, when relay 7 is energized and the arms 4a and 4b make contact with terminals 5a and 5b, respectively. In the first ernbodiment, the controlling circuit fed by lines 5 serves to close the contacts of the electric shock releasing switch 270 automatically by the energization of an alternating current shock relay coil 12 with the changing of position of switch arms 4a and 4b of the separating switch 4.

In the second embodiment of the invention, relay coil 12 of releasing relay 27 is energized, and the shock voltage is synchronously released by a phase of the heart action voltage. This occurs rwith switch arm 113a of manually-operated switch 13 in the position shown in the figure. Which alternative embodiment 'will be used has to be decided by the physician. Thus, the current feeding relay coil 12 will flow through line 5, switch arm 13a, contact point 13e, lead 15d, and switch 45 when closed by relay coil 45h after being triggered by a heart action pulse through trigger device 15.

Separating switch 4 and releasing switch 27, therefore, are coupled together in such a manner that they are actuated or controlled by the voltage controlling circuit essentially in what may be called a contrary sense. That is, when the arms 4a and 4b of switch 4 make contact as shown in the figure, and cause a charge to accumulate on the plates of capacitors C1 and C2, the switch arms 27a and 27b of switch 270 are open, also as shown in the figure., and prevent a simultaneous discharge of the Storage capacitors C1 and C2. But releasing switch 27 is closed only if the arms 4a and 4b of switch 4 are at contacts 5a and 5b at this time, since it is not desired to simultaneously charge the storage capacitors. In order to ensure that the tlwo switches 4 and 27 cooperate in this manner, contacts 5a and 5b of the separating switch 4 serve as operating contacts of the controlling circuit, through lines 5, for the releasing switch 270. The lines 5 also being connectable to the AC supply 32, the supply current is conducted either only into the primary coil 3P of the high voltage transformer 3 or only into the controlling circuit through lines 5.

In order to be able to choose between these two methods of controlling the release of a shock voltage to the body of the patient, that is, either synchronized or not synchronized with the heart beat, a manually-operated single-pole, double-throw synchronization switch 13 is inserted into the controlling circuit. By means of this synchronization switch 13, the output of the triggering' device 15, synchronously triggered by pulses derived from the heart voltage, may complete the circuit to the controlling lines.

If the 4controlling circuit through lines 5 is energized directly to the AC shock relay coil 12, with the arm 13a of switch 13 in a position other than that shown in the figure, relay 12 can be actuated only after the charging of the storage capacitors C1 and C2 has terminated, and then it instantly causes the closing of the releasing switch 27. Switch 13 is actuated when desired by the attending physician.

If it is desired to control the release of the electric shock voltage by a phase of the heart action voltage, a triggering device 15 is inserted to be used in conjunction Lwith the controlling lines 5, thus causing the actuation of the triggering device 15 only after having received a pulse, for example corresponding to the peak of the R-phase of the heart voltage. The heart voltages are picked up by electrodes at the body of the patient 33 and conducted through monitoring leads 16 to a monitoring amplifier 15a of the kind used with electrocardiographs. From the amplified signals, triggering device 15 derives a pulse in a desired time relationship to a marked phase of the heart voltage, for example the R-peak. This pulse is fed to the coil 45b of rela\y 45, so that switch arm 45a closes line 15d, thus feeding current through the AC shock relay 12, so that the AC shock relay coil 12 is fed with current. Direct current from direct current supply source 36 is fed through lines 37. Switch 38 must be closed if the monitoring amplifier 15a and trigger device 15 are to be energized.

It may be desired and useful to couple the adjustable arm 34 of the output voltage controller circuit with the adjustable arm 31 of the variable transformer 30 connected to the alternating current supply lines, in order to be able to control both synchronously, for example by means of the actuating knob 35a. If it is desired to increase or decrease the value of shock voltage developed across the storage capacitors C1 and C2, and across the charge storage lines 18a and 1811, with line 181) being a reference point, consideration must be given to the relation or ratio of the resistors R1 and R2 of the volt-l age divider of the voltage controller.

An increase in the charging voltage across the series combination of charging condensers C1 and C2, caused by an increase in the voltage betlween arm 31 and the common reference point, line 1b, of the primary AC circuit, causes an increase in the rate at which these condensers are charged and decreases the time for reaching the breakdown voltage across glow discharge tube 25, In order that the charging times remain substantially equal and independent of the adjusted shock voltage with increasing total charge voltages, the voltage developed across the active part of R2 must be decreased. This is accomplished by moving lever 34 downwards, thereby decreasing the active part of R2. The coupling member 35, controlled by actuating knob 35a, between both these adjusting elements, one for the variable transformer 31 and the other for variable resistor R2, therefore, must actuate the taps 31 and 34a in a contrary sense with respect to each other.

In the prior art, the shock voltage had to be built up first, and then the shock voltage was released, this taking a few seconds of time. By means of the construction of the defibrillator according to the invention, the shock voltage can be released a short time after supply control 2c is actuated. The time interval after charging the storage capacitors during 'which time there is an element of danger for the attending personnel, can be shortened, for example, to from l to 2 seconds.

It is particularly advantageous that the value of the desired shock voltage can be chosen and adjusted by the variable arm 31 of transformer 30 before the storage capacitors C1 and C2 have been charged. Changing of capacitors C1 and C2 is started by bringing movable arms 2a and 2b of switch 2 from the positions shown in the ligure to their other position, thus completing the AC circuit through supply lines 1a and 1b. Not only is the moment for releasing the shock voltage, therefore, determined by the attending physician but also the charging of the capacitors does not have to start sooner than this moment. This procedure also has the advantage that at any time before releasing the debrillation or shock voltage by actuating switch 2, the physician can still choose other values of energy or voltage, without the necessity that the storage capacitors C1 and C2 rst have to be discharged and then again recharged.

The time delay of the shock voltage caused by duration of the necessary charging of the storage capacitors, by about one second at the utmost, is not a serious disadvantage. Moreover, since the AC shock relay 12 can be synchronously controlled by natural heart action, and with an average heart pulse frequency of approximately 60 perminute, the shock voltage appears under any circumstances only about once each second. The short charging time moreover also makes possible a series of shock voltages within a short time by actuating the supply control 2c of switch 2 in the desired rhythm or motion.

If for any reason, after charging the storage capacitors C1 and C2, the shock voltage should not be released, short-circuiting lines 41 and 43 shunting capacitor C1, and short-circuiting lines 41 and 42 shunting capacitor C2 can be closed by switch arms 47a and 47h of switch 47, also actuated by supply control 2c. The physician need only to stop to press or push this control 2c so that the movable arms 47a and 471) would be returned to the position shown. Thus the dangerous charge would be internally discharged through resistances 39 and 40.

The photoelectrical coupling between the voltage controller and the controlling lines 9 and 10 has the advantage that the controlling lines are, from the standpoint of a direct electrical connection, separated or isolated from the charge storage and discharging lines 18a and 18b conducting a current at a relatively high voltage, thus making provisions for a simple and inexpensive isolation between the two. Therefore, the application lines 17a and 1711, which apply the shock voltage, are also laid out in a oating manner, and the electrodes 29a and 29b need not be grounded to any specific reference point, thereby eliminating a possible shock hazard.

There is another advantage in this circuit insofar that the rectiers D1 and D2 remain connected to the application lines 17a and 17b even after the shock voltage has been released. This feature ensures that the voltage across the storage capacitors C1 and C2 does not transiently change polarity during the discharging phase. This guarantees that the shock pulses are purely of one polarity. If this would not be the case, aperiodic oscillations could occur, if the external resistance represented by the patient 33 was below a certain minimum value. An oscillating discharge during the application of the shock voltages is very undesirable from a physiological standpoint. Therefore, the construction of direct current debrillators according to this invention leads to essential progress and is very advantageous in several aspects.

It is to be understood that the above-disclosed arrangements are illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention, which is to be limited only by the appended claims.

What is claimed is:

1. A direct current defibrillator, for producing shock pulses to be applied to a patient, comprising:

alternating current supply means;

electrode means adapted to be connected to said patient for applying shock pulses to said patient;

shock voltage means for developing shock pulses to be applied to said patient, said shock voltage means including storage capacitor means for storing said shock pulses;

switching means, having an input and first and second outputs, said input connected to said alternating current supply means and said rst output connected to said shock voltage means for transferring the alternating current from said alternating current supply means to said shock voltage means;

controlling means connected to said shock voltage means, said controlling means responsive to a desired charged state of said storage capacitor means and for disconnecting said switching means from between said alternating current supply means and said shock voltage means; and

application means respectively connected to said second output of said switching means and said shock voltage means for applying said shock pulses to said electrode means.

2. A direct current delibrillator as recited in claim 1 wherein said controlling means comprise:

pulse means for developing pulses in response to the desired charging of said storage capacitor means;

a photo-electric device positioned adjacent said pulse means for detecting the pulseinitiated by said pulse means;

a pulse amplifier connected to the output of said photoelectric device for amplifying the detected output pulses of said photo-electric device; and

relay means connected to the output of said pulse amplier for actuating said switching means.

3. A direct current debrillator as recited in claim 2 wherein said pulse means includes a glow discharge tube.

4.V A direct current defibrillator as recited in claim 1 wherein said shock voltage means further includes a tapped transformer, a resistive tapped divider across said storage capacitor means, and a common control wherein the respective taps of said tapped transformer and said resistive tapped divider are connected to said common control so that the respective voltage from each respective tap to their respective reference points change inversely upon adjustment of said common control.

5. A direct current debrillator as recited in claim 1 wherein said application means comprises:

responsive means adapted to Ibe connected to said patient for detecting peak voltage in successive cycles of heart muscle activity; and

means connected between said switching means and said responsive means for permitting application of said shock pulses to said patient in relation to said detected peak voltages.

6. A direct current defibrillator as recited in claim 5 wherein said means includes selective means for permitting selective application of said shock pulses to said patient in either a synchronous or asynchronous relationship to said detected peak voltages.

References Cited UNITED STATES PATENTS 3,236,239 2/1966 Berkovits 128-419 3,258,013 6/1966 Druz 12S-419 WILLIAM E. KAMM, Primary Examiner 3"050 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,513,850 Dated May 26 1970 Inventor(s) Paul weber It is certified that error appears in the above-idetifiled patent and that said Letters Patent are hereby corrected as shown below:

r- Column l, line Sl: "ltoter" should be --latter Column 4, line 28: "it" should be -its Column V4, line 40: "11:13u" should be -l3a SIGNED MTD SEALED sEP 15m (SEAL) Attest:

Edward M. Fletcher I1'- Timm r. JR. Attestmg Offir Gomissioner of Patents

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