US2782786A - Electrocardiograph electrode with absorbent contact surface - Google Patents

Description

L. R. KRASNO Feb. 26, 1957 ELECTROCARDIOGRAPH ELECTRODE WITH ABSORBENT CONTACT SURFACE Filed Odt. 10, 1955 INVENTOR Louis R. Krasno ATTORNEYS forming a body of molded calcium sulphate.

United States Patent 6 ELECTROCARDIOGRAPH ELECTRODE WITH ABSORBENT CONTACT SURFACE Louis R. Krasno, Pensacola, Fla.

Application October 10, 1955, Serial No. 539,444

4 Claims. (Cl. 128-417) This invention relates to electrode structures and particularly to electrodes for establishing electrical contact with the skin of a patients body for electrocardiographic tests.

Heretofore it has been common practice to provide a rigid metal electrode for electrocardiographic purposes, to establish electrical contact with the skin of a patient.

A metal surface placed against dry skin does not estab-.

lish a satisfactory electrical contact and so it is the practice to coat the contact surface of the electrode with a suitable conductive paste and to secure the electrode to the patients body in a suitable manner. In many instances the chemical content of the paste and/ or concentrated pressure between the metal electrode and the patients skin causes irritation and in some cases actual damage. Also, unless the metal electrode is securely held in place, the paste used acts as a lubricant and the electrode tends to slide about. It has been proposed to establish electrical contact with a patients skin, for the purpose of electrotherapy by moistening a pad of fibrous material to be placed against the skin to establish electrical contact. Such pads of fibrous material, however, were not uniformly absorbent and are so readily distortable that the conductivity between the pad and the patients skin is not reliable or uniform.

According to the present invention electrical contact is established with a patients skin through a body of absorbent material, which body is substantially rigid. A highly satisfactory electrode has been constructed by Calcium sulphate is commonly known as plaster of Paris. This material may be readily molded to any desired shape without special equipment and when the material sets it forms a substantially rigid body highly absorbent and self sustaining. Such a body may have a suitable clip or terminal post imbedded therein or otherwise electrically connected thereto and constitute an electrode for engaging the patients skin. A supply of such electrodes may be made up in advance and allowed to dry completely. For use it is only necessary that the electrode be dipped inwater whereupon the absorbent body of plaster absorbs a sufiicient quantity of water to make it readily conductive to electricity without causing the electrode to dis integrate. Commercially available plaster of Paris (calcium sulphate) is usually provided with a minor proportion of sodium chloride (table salt) mixed therewith. The proportion of sodium chloride may be varied to produce a slow setting or fast setting plaster. When such a mixture is used for molding electrodes according to the present invention, the dipping of the electrode in water causes ionization of at least some calcium sulphate and thus renders the electrode conductive, in addition, some of the sodium chloride goes into solution and thus aids in rendering the absorbed moisture highly conductive. It is not necessary, however, that the electrode contain sodium chloride since the ionization of the calcium sulphate alone is suflicient to make the water suitably conductive. In any event, the electrode could be moistened in a saline solution if necessary. It is not necessary that water be used as the moistening agent. Any suitable conductive liquid, not irritating or harmful to the skin, may be used.

It is not necessary that calcium sulphate specifically be employed for the electrode since any suitable absorbent solid body may bevused.

Among the advantages of the present electrode is the fact that it may be produced by unskilled persons without special equipment, and furthermore that the contact surface may be scraped, carved or molded to any desired surface configuration to snugly embrace any desired portion of the patients body in snug surface contact throughout the area of the electrode without enforcing distortion Another object of this invention is to provide an electrode for the purpose described which is of extreme-simplicity in construction, and highly economical to produce. Still another object of this invention is to provide an electrocardiograph electrode having a contact surface and connecting means readily adaptable to many diverse types of electrical apparatus.

It is a further object of this invention to provide an electrode having uniform and dependable conductivity.

A still further object of this invention is to provide an electrode having a rigid contact portion readily modified to conform to different body contours.

Additional objects and advantages will appear to those skilled in the art as the description proceeds in connection with the accompanying drawings wherein:

Fig. 1 is a perspective view of an electrode embodying the present invention;

Fig. 2 is a view of the electrode of Fig. 1 shown applied to the arm of a patient;

Figs. 3 and 4 are similar perspective views of modified forms of electrode illustrating the use thereof with handles for manually holding the electrodes in place;

Fig. 5 is a partial sectional view of a still further form of electrode embodying the present invention; and,

Fig. 6 is a vertical sectional view, with certain parts shown in elevation illustrating a still further embodiment of the invention.

Referring first to Fig. 1, the electrode body 2 comprises a molded rectangular body of suitable absorbent material such as plaster of Paris having an electrical con-.

nector clip 4 secured thereto by having a portion thereof imbedded in the material of the body 2. The body 2 is further provided with an attachment member-"6 located substantially centrally thereof and comprising a peg int 1 bedded in the body of the electrode and having a reduced shank portion 8 and an enlarged head 10. Theittta'chment member 6 is preferably of no'nconductive material a ea-res whereby it may be held by any suitable instrumentality agsiast'me body or apatint without afie'cting the electrical characteristics thereof. As stated, the body 2 may be of molded plaster of Paris, which is highly absorbent. When it is desired to use the electrode for electrocardiographic purposes the body 2 is dipped into any suitable supply of water (or other suitable liquid conductor) whereupon the body absorbs a considerable quantity of the water throughout. With the saturated plaster ,body placed against the skin ofa patient, very'good 'electrieal contact is made with the patients skin and the electrode may be connected, by means of conductor 12,. to the'desired indicating or recording apparatus, in' the usual m r Fig. 1 shows a rectangular block of absorbent material and a large supply of such blocks maybe madeup in advance. Whenit is desired to'apply the electrode to. a portion of the patients bod'y that does not present a substantially fiat surface for contact, the contact surface of the electrode (that surface at the bottom of the block shown in Fig. 1) may be scraped or carved toa shape complementary to the desired portion of the patients anatomy and placed thereon to make goodfsurface contact throughout asubstantial area without unduly'distort g the patients fleshor applying high localized pressure at any point.

Fig. 2 merely illustrates the adaptability of the ,elec: trode of Fig. l'for application to any portion ofthe'patients body. As shown in that figure the electrode 2"is held against the patients forearm 14 by means of'the resilient clip 16. The clip 16, which is preferably "of nonconducting material, is of generally bowed shape hay: ingQa slot 18 in one. Qfldthefeof and .a resilient armfzo at the other end. The slot 18 may be positioned to embrace the shank portion 8 of the attachmientb, with the resilient arm 20 extending around the'pat'ients forearm to'engage the opposite side thereof and thus securely hold the electrode 2against the patieritsQskin. Clearly,'aj clip like that of Fig.'2 may be made of a y size necessary to hold he electrode'against .any selected portion'of theiphtients Figs. 3 and 4 illustrate alternativeforms of electrode wherein, in .Fig. 3 the absorbentbody 22 has imbedded. therein a portion of a binding post 24. The binding post 24 is provided with a reduced shank portion adapted to frictionally receive a slot in the shank26 of a handle 28. Preferably the shank :26 and/or handle 28 are ofnonconductive material. The terminal post 24 isfurther provided with a transverse opening 30 to receive a conductor,

such as the conductor 12 of Fig. 2, and a clamping screw 3 2 for securely clamping the'conductor in the" binding post. In the form of Fig. '3 theelectrodeniay Be held against the patients skin by means of thelhan'dle 28 or it may be heldi'n the manner indicated inFig'. 2. It'is to be understood that any suitable clip' 'oriother holding means may be provided to hold the, electrode :of the present invention against the patients bodysincethe invention is not limited tofany specific type ofsecuring or holding means.

Fig. 4 shows a further form. the electrode may take wherein the absorbent body is of frustoconical shape whereby the contactsurface 3 6may bevery small and infact mayleyenl approacli alcontact point where it is desired'to perform tests over a very small'area of the patientsskin. The. binding post 24and the handle 26- 28 of? this form, may be identical. to, those .shown in Fig. 3.

.8 tion an body- 38 of absorbent, material is carried bya suction cup},40 on theinner .side thereof and.presents .,a.concayecontact face 42 tofthe patients skinwheninplacelhereon. -The suction cup 40 is .preferablyof.metalandprovided witha connecting tube44 communicating .with the interior thereof andupon which a Iubbenor .the i like bulb 46 is telescopicallfmounted.

. '5 's'howsastill further adaptation of the inyen" The metal tube 44 may also support a conductor clamp 48, as shown, in electrically conductive contact with the tube 44 and cup 40. The electrode of Fig. 5 is held against the patients skin by suction. In use, the suction cup 40 is first dipped in water so that the absorbent body 38 becomes moist and conductive and then the bulb 46 is collapsed to expel a large portion of the air therefrom. While the bulb is held in collapsed condition the periph cry of the suction cup 40 is placed against the patients skin and while being held there, the bulb 46 is released to expand and establish a partial vacuum within cup 40. The partial vacuum in the cup 40 and bulb 46 serves to hold the electrode securely against the patients skin as long as desired. Since the porous or absorbent body 38 is not impervious to air, it is necessary that the peripheral edge of the suction cup 40 be in actual contact with the patients skin to provide a suitable hermetic seal therewith.' For that reason the outer periphery of the concave contact surface 42 substantially coincides with the peripheral edge 50. It is desirable that no abrupt change in direction exist at the juncture of the edge 50 and surface 42 which abrupt changes in direction would result in undue distortion of the patients skin and possible damage thereto. By providing the concave surface 42, the patients skin and flesh may be drawn slightly inwardly of thecup 40 into firm surfaced contact with the moist absorbent body 38 and thus establish good electrical contact'therewith'. i Y

""Fi'g'. 6Isho'ws a still further embodiment wherein an absorbent body' 52 is supported by asupporting cup 54. The: supporting cup 54 has a binding post 24'pe'rmanently mounted thereon and provided'with areduced shank .56 adapted to 'frict'ionally receive the slotted portion ofa suitable holding means 58 (shown in dotted lines). .The absorbent body 52 may be placed in the supporting cup 5 4'ivhilein a plastic state and molded therein to define a contact' s'urface '60 of any desired configuration. After the material is" set the electrode is ready for use in the described manner. The form shown in Fig. 6 olferssoine advantages in; that the absorbent body 52 may be molded in place therein without Qthfe necessity of providing any mold, such aswould be necessary for the forms of Figs. 1 through 5. The provision of the absorbent body'52 of Fig. 6 maybe accomplished at any place without molds or tools by merelyforming the usual plaster of Paris mixture with water, placing it in the supporting cup 54 an'd'molding'the contact surface by hand.

While a limited number of embodiments of the invention have been "shown and described herein it isto be understood that these embodiments are merely illustrative and that the invention is not limited thereto. It is contemplated that the invention encompass all modifications falling fairly within the scope of the appended claims. v

.1. An electrocardiograph electrode comprising; a substantially rigid, porous and self-sustaining body of calcium sulphate, and an electrically conductive connector secured to said body, said body having an exposed face for contact witha te'st'surface." V

2. An electrocardiograph electrode comprising; an electrically conductivelrig'id supporting body having means thereon for connection to an electrical conductor, said electrode having a" contact surface thereon for engagement with' a surface't'o be electrically connected thereto, said contact surface be'ing defined' by a substantially rigid body of calcium "sulphate secured to said conductive supporting body.

3." An electrode as defined in claim 2, wherein said supporting body comprises ainetal suction cup with means for creating a partial vacuum" therein, said body of material being an annular body inside said suction cup and having a concave contact surface withiits outer periphery substantially coincident with the open peripheraledg'e' of said suction cup.

References Cited in the file of this patent UNITED STATES PATENTS Horton June 23, 1896 Moses Apr. 13, 1911 Speter May 25, 1926 Jensen May 29, 1951 Welsh Jan. 1, 1952 Leech Dec. 16, 1952 FOREIGN PATENTS Switzerland Apr. 15, 1951

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