US2410499A - Stimulator - Google Patents

Description

Nov. 5, 1946.

. J. c. HINSEY ET ALI- STVIMULATOR Filed May 16, 1945' 5 Sheets-Sheet 1 l mw fl m, e G e MH z m fi 50 ma Nov; 5, 1946.

J. C. HINSEY EIAL STIMULATOR Filed May 16, 1945 3 Sheets-Sheet 3 5 wueml'om n .v mug. m mw Q an A c 3 W W/Q W Jase Patented Nov. 5, 1946 U ITED STATES PATENT 'Geoheg'an, Mamair'oneck,

N. Y., assignors to the Government 'of'the United States Application May 16, 1945, Serial No. 594,046

3 Claims. Thisinvention relates generally to stimulating apparatus but more particularly to a neurological stimulator designed primarily for use in the operating room when it is desired to stimulate various parts of the nervous system eitheras a means of exploration or in experimental work. 7 H

One object of the invention is to provide a stimulator in which the nature and strength of the stimulus can be accurately controlled and duplicated whenever necessary; f I

An'other object of the invention is to provide a stimulator which operates on an alternating current of constant frequency and wave form.

Another object of the invention is to provide a device of the class described which provides a stimulus of constant uniform strength. v

V A further object of the invention is to provide a stimulating device of the class described which is of simple construction and which may be easily operated with a maximum of safety.

With these and other objects in view, the invention consists of the construction and the combination of parts as well as of the detail an'dar-Q rangement of parts as will be more particularly set forth in the specification relative to the .accompanying drawings.

Referring to the drawings in which like parts are in'dicated'by similar reference characters;

Figure 1 is a perspective view showing the entire apparatus mounted in a container havin side compartments forthe connecting cords;

Figure 2 is a plan View showing the under surface of the lower panel and thefarrangement of thevarious electrical elements thereon;

Figure 3 is a perspective view o f'the fuse housing showing the fuses, a lower portion of the power switch and filters; and

Figure 4 is a diagrammatic View showing the electrical circuits of the apparatus.

Briefly stated, the device comprises a stimulator which is operated by the ordinary house current, and which furnishes uniform stimulation at a predetermined voltage, wave form and frequency.

It is frequently'important thatthe surgeon know the effective strength of the 'stimulushe is delivering, for example, if he stimulates a motor nerve central to an inj ry and fails to elicit a response from the muscles it is important that he know whether this failure of response is due to nerve injury or to an inadequate stimulus; It is further important that the stimulus be such that its nature and strength can be accuratelyrecorded'and duplicated by other workers.

Much of the previous Work of stimulation has been done with the Harvard Inductorium. "With 2 this apparatus, wave form and frequency are subject to wide variation from day to day and even from minute to minute. The voltage delivered varies widely with the resistance of the tissues stimulated and may also change materially as the battery ages. Thyratron and similar stim ulators supply relatively uniform frequency and wave form over awshort period but do not hold their calibration well. In addition, the voltage delivered under no-load conditions is apt to be much higher than that under actual stimulating conditions and for accurate results the voltage must be measured by means of a-cathode'ray oscillograph orvacuum tube voltmeter during-stimulation. Sixty cycle sine wave stimulators have: been used previous to this invention but in general, while they maybe safe for use by someone familiar with their construction, they are notsafe for use routinely by surgeons not familiar with electrical apparatus.

Effectiveness of a stimulus depends upon frequency, wave form and voltage delivered at the electrodes during stimulation. Frequently, reported results of stim'ula'ting various parts of the nervous system are of little or no value'to other workers because the conditions of stimulation are not stated completely or accurately. For example, the v'oltage may be stated withoutmention' of whether it was measured atno-load, or during stimulation, and in the case of stimulators with high source-impedance, there may be a wide difference between the two. .Where a sine wave stimulus was used, it is frequently not clear whether it was measured in root mean square volts, or peak-to-peak volts. It is seldom convenient to measure an characteristics of the stimulus in the operating room. The instrument described herein, which is designed to operate from 100120 volt, 50-60 cycle power-lines, derives the stimulus directly from the power source, and the voltmeter for the range in use (which reads in R. M. S volts) is connected directly across the electrodes. It is necessary, therefore, only to read the voltmeter during stimulation to present a clear statement of the stimulus employed. Anappropriate statement would bev as follows: The stimulus employed was a sixty cyclesine wave at 1.6 R. IVLS. volts, measured under load.

The instrument has a low source-impedance so that the voltage under load will: ordinarilydeviate only slightly from'the no-load. setting.

To assure safety in the operation of the device, the line voltage is passed through twotransformers before application to the patient to pre-. vent direct contact with the line even'inthe event standpoint of accidental shock than are most electrical instruments used in operating rooms. The device is adapted for use with a high and a, low range of voltages. The low range will be adequate for most work, and should be used The high range is intended wherever possible. primarily for stimulation of the sensory cortex where 15-20 volts may sometimes be required.

The high range should not be used on thefmotor cortex.

. To furnish power supply, the instrument may be plugged directly into any 100-120 volt, 50-60 cycle A. 0, outlet. It may be operated from 200-240 volt supplies by the use of an appropriate step-down auto-transformer. The power supply ground is used to dissipate static charges. The instrument should, therefore, be used on power supplies which have one side grounded, and the step-down transformer, if used, should be of the auto-transformer type.

The instrument is protected by one-ampere fuses, mounted beneath thepanel. These should blow only if the instrument itself develops a defeet, or if it is plugged into the wrong type of power supply. Access to the fuses may be obtained by removing the six front-panel screws, and lifting the panel out of the case Spare fuses are provided, and will be found; in clips near the working fuses.

i The apparatus includes an input circuit and an output circuit which are inductively coupled bytwo transformers. Referring to Fig. 4, which shows a-diagrammatic outline of the circuits, the numerals 10 and 11 indicate the terminals of a plug l2 which is adapted to be inserted into a wall socketor other connection tocouple the apparatus to the usual 110 volt A. 0. current supply. The terminal I is connected through the conductor- H to fuse 14 which in turn is connected through conductor l to the terminal l5 of the primary coil [6 of the transformer IT. The other plug terminal H is connected through conductor l8, fuse l9, conductor 20, switch 2| and conductor 22 to the terminal 23 of the primary coil I5. The numeral 24 indicates the secondary coil of the transformer IT. The terminals 25 and 26 of the secondary coil 24 are connected through conductors 21 and 28 to terminals 21' and 28' of primary coil 29 of the transformer 30. The trans; former 30 is provided with a split secondary coil 3| which is provided with terminals 32, 33 and 34 and which functions to effect a greater. and a lesser degree of stimulation aswill be further described. The major portion 0f the Split secondary coil 3| is connected to terminals 32 and 33 which in turn are connected respectively to switch terminals 35 and 3B. The terminal 34 of the minor portion of the split secondary coil 3| is connected to the fixed resistance 31.

To place a portion of the secondary coil 3| or the entire secondary coil in' the stimulating circuit a switch 38 is provided. This switch is of the cam operated type and provided with two blades 45 and 44 whichareadapted to contact simultaneously. either the terminals 36 and 39, or terminals 35 and 40. t v

The fixed resistance 31. is connected between the terminal 34 of the secondary coil, 3| andthe terminal 4| of a variable resistance 42 of a'rheo- 7 resistance 81 and condenser 88, is inserted in the 4 stat 43 (see Fig. 2). The other end of the variable resistance 42 is connected to the switch blade 44. The switch blades 44 and 45 of the switch 38 are connected by a conductor 45 which in turn is connected through conductor 41 to switch blade 48 of the magnetic switch or relay 49 as will be further explained.

It will be noted that the switch blade 44 is adapted to contact the switch terminals and 36, and switch blade is adapted to contact switch terminals 39'and 40. These blades 44 and 45 operate simultaneously so that by setting the blades on the desired pair of contact terminals the circuit may be completed through either the terminals'36 and 39 or the terminals 35 and 4B.

The switch blade 5|! of the rheostat 43 is connected through conductor 5| to switch blade 52 of an electromagnetic switch or relay 49. The switch blades '48 and 52 of the relay, when actuated by energization of magnet 53 thereof, contact terminals 54 and 55, and connect the leads 4! and 5| through conductors 56 and 51 to the two applicator electrodes 58 and 59 of the handpiece 60. The conductors 56 and 51 are bridged by a resistance and a resistance 5'! is connected from conductor 51 to conductor 5|.

The magnetic switch on relay 49 comprises a central magnetic core wrapped by a coil 5| connected to the terminals 62 and 63. The terminal 52 is connected through conductor 54 to the terminal 65 of the push button switch 66 and the terminal 63 is connected through the conductor 61 and thence through conductors 68 and 21 to terminal 25 of the secondary winding 24 of the transformer IT. The other terminal 63 of the switch 66 is connected to terminal 26 of the secondary winding 24 of the transformer IT by means of conductors I0 and 28.

In order to energize the magnet53, the button 1! of the push button switch is pressed inwardly thus spreading apart the contact members'l2 and '13, which are connected by conductor 13', until they are in contact with the stationarycontact members 14 and 15, allowing current to pass through the conductively connected contact members 12 and I3 to thus complete, the circuit from the power lines 21 and 28- through the coil 6|. J

The filament terminals I1 and 18 of a pilot lamp 19 are connected to the conductors 68 and 1'0 so that the lamp remains lighted so long as the instrument is plugged into a source of power and the power switch is turned on.

The conductors 4'1v and 5| which are adapted to be connected to the electrodes to furnish the desired stimulation may be bridged by either of two voltmeters which are designated by the numerals and BL'depending on the setting of blade 45 of switch 38. Of these voltmeters, 8| is for a high range measurement and 80for a low range. When bridging voltmeter 8| across the lines 47 and 5|, the connections are through conductor 45, switch blade 45, conductor 82, volt meter 8|, conductor 83 to conductor 5|, and when bridging voltmeter" 80 across the lines 41 and 5| the connections are through conductor 46, switch blade 45, conductor 84, voltmeter 80, conductor 85 to conductor 5|.

Five filters, each consisting of a condenser anda resistance are used to filter out high frequency currents which may be picked up by the line: from generators, X-ray, radio apparatus, and similar;

sources of interference. Filter 83, consisting of return line designated by the numerals 89 and 99; filter 9|, consisting of resistance 92 and condenser 93, is inserted between conductor I5 and conductor 90; and filter 9Q, consisting of resistance 95 and condenser 96, is inserted between conductors 22 and 99. Filters are also inserted in the output circuit in proximity to the stimulating electrodes and the relay. Filter 91, consisting of resistance 98 and condenser 99, bridges conductors 67 and 5|, it being connected to conductor 91 by conductor I09, and filter Iill, which comprises resistance I02 and condenser I133, is inserted between conductors I! and I09, the latter being connected to conductor 6?. The foregoing resistances along with resistances 56' and 51 provide a leakage path for dissipation of static charges so that such charges cannot collect on the electrodes.

A foot switch (not shown) may also be used to control the circuit of the electrodes. Terminals I64 and I05 for connection of a foot switch are therefore provided.

The apparatus is contained within a casing I06 which is'divided into a main central compartment It? and two small side compartments I98 and I69 which are provided for retention of the input and electrode conductors l3 and I8, and 56 and 51, respectively. The various elements of the apparatus are attached either to an upper panel H9, a lower panel II I or the side walls H2 and H3 which, with the lower panel and the front and a side wall of the casing, form a small insulated compartment to enclose the fuses I4 and I9, power switch 2|, and filters 9i and 84. The spaced upper and lower panels H9 and I I I, as shown in Fig. 3, provide for the better arrangement and protection of the wiring between the various parts of the apparatus.

The casing or cabinet is provided with a hinged lid, a carrying handle, and locks so that the apparatus may be readily transported and protected.

Having thus described our invention, what we claim as new and wish to secure by Letters Patent is:

1. A stimulator of the class described comprising an input circuit, high frequency filters associated with said input circuit and means for connecting said circuit to a source of alternating current of predetermined voltage, wave form, and frequency, having one side grounded, a transformer circuit including input and output transformers provided with primary and secondary coils, an output circuit, high frequency filters associated with said output circuit, applicator electrodes included in said circuit, means for selecconnected with said transformer circuit, an electromagnetic switch and a manually operated switch included in said output circuit adapted to control the operation of said electrodes.

2. A stimulator of the class described comprising an input circuit, high frequency filtering means associated with said input circuit and means for connecting said circuit to a source of alternating current of predetermined voltage, wave form, and frequency, having one side grounded, a transformer circuit including input and output transformers provided with primary and secondary coils, an output circuit, high frequency filtering means associated with said output circuit, applicator electrodes included in said circuit, a switch circuit connected to said transformer circuit,'a two-way switch connected to said output circuit, said switch adapted to selectively connect said output circuit with groups of secondary coils of said output transformer, a high frequency filter associated with said switch circuit, meters for measuring high and low range voltages bridging said coil groups, an electromagnetic switch, and a manually operated switch included in said output circuit adapted to control theo-peration of said electrodes.

3. A stimulator of the class described comprising an input circuit, high frequency filters associated with said input circuit and means for connecting said circuit to a source of alternating current of predetermined voltage, wave form, and frequency, a transformer circuit including an input transformer provided with a primary and a secondary coil and an output transformer provided with a primary and a split secondary coil, said split secondary coil being adapted to provide a greater and a lesser degree of stimulation, an output circuit, high frequency filters associated with said output circuit, applicator electrodes included in said circuit, means for selectively connecting said'output circuit with groups of secondary coils of said output transformer, meters for measuring high and. low range voltages bridging said coil groups, a switch circuit connected with said transformer circuit, an electromagnetic switch and a manually operated switch included in said output circuit adapted to control the operation of said electrodes. 1

JOSEPH C. I-HNSEY. WILLIAM A. GEOHEGAN.

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