US3469577A - Scalp contacting bioelectrode - Google Patents

Description

Sept. 30, 1969 J. A. R. KATER 3,469,577

SCALP CONTACTING BIOELECTRODE Filed March 2, 1967 3e 4o 36 4o 48 5 3 I 4 \50 I, A I

60 JIIOHN A. R. KATER Fla. 7 INVENTOR.

ATTORNEY United States Patent 3,469,577 SCALP CONTACTING BIOELECTRODE John A. R. Kater, Diamond Bar, Calif., assignor to Beckman Instruments, Inc., a corporation of California Filed Mar. 2, 1967, Ser. No. 620,011 Int. Cl. A61b /04; A61m 35/00 U.S. Cl. 128-21 9 Claims ABSTRACT OF THE DISCLOSURE A bioelectrode for attachment to the scalp of a subject without removing hair from the scalp. The bioelectrode is generally in the form of a ring, having a slot therein so that hair on the scalp can be readily passed through the slot into the opening in the ring. Means are provided for securing the ring to the air so that the ring is held in physical contact with the scalp.

This invention relates to means for establishing conductive contact with the scalp of a living subject and, more particularly, to a bioelectrode and method for applying the same to the scalp of a subject for electroencephalographic potential measurements.

In electroencephalography (EEG) a bioelectrode is attached to the scalp of the subject to establish conductive contact with the scalp in order to measure brain waves. Present techniques for attaching such electrodes to the scalp include glueing the electrode to the scalp with cement, collodion or other adhesives, the use of low melting paraffin and special head frames to hold the electrode to the scalp under light pressure. These methods are messy and cumbersome, the main obstacle being the hair on the scalp. Heretofore, the only alternative to the above method for applying electrodes to the scalp was the shaving of the scalp to remove the hair so that the electrodes could be applied directly to the scalp in a conventional manner utilizing thin adhesive discs. However, for obvious reasons many subjects do not care to have their heads shaven for electrode attachment purposes.

It is, therefore, the principal object of the present invention to provide improved method and means for establishing electrical contact with the scalp of a subject.

Another object of the invention is to provide an improved bioelectrode for attaching to the scalp of a subject without removing the hair from the scalp or requiring the use of cements, adhesives, paraflin or the like.

According to the principal aspect of the present invention, there is provided a bioelectrode having a central opening therethrough which is positioned in physical contact with the scalp of the subject with hair from the scalp passing through said opening. The opening in the bioelectrode is then filled with an electrolyte and the bioelectrode secured firmly to the scalp by either tying the hair passing through the opening in the bioelectrode into a knot above the bioelectrode or applying a cap to the bioelectrode clamping the hair between the cap and the bioelectrode. Thus, the hair of the subject is utilized as an anchor for the bioelectrode establishing firm contact between the bioelectrode and the scalp thereby reducing possible motion artifacts. Consequently, no hair need be removed from the scalp of the subject, nor are cements, adhesives or head frames required for maintaining the bioelectrode in firm contact with the scalp.

Other objects, aspects and advantages will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of one form of the bioelectrode of the invention.

FIG. 2 is a perspective view showing the bioelectrode of FIG. 1 secured to the scalp of a subject in accordance with the present invention;

FIG. 3 is a cross-sectional view of another form of the bioelectrode of the invention;

FIG. 4 is a perspective view of still a further form of the bioelectrode of the invention which comprises a circular member and a cap which are shown unassembled;

FIG. 5 is a cross-sectional view of the bioelectrode shown in FIG. 4 with the cap and circular member assembled;

FIG. 6 is a cross-sectional view of the bioelectrode illustrated in FIG. 5 shown attached to the scalp of a subject; and

FIG. 7 is a cross-sectional view of still a further form of the bioelectrode of the present invention.

Referring now to the drawings in detail, FIGS. 1 and 2 illustrate one form of the bioelectrode of the invention, generally designated by numeral 10. The bioelectrode comprises a generally circular member 12 having an opening 14 extending vertically through the membrane forming an electrolyte reservoir. The member 12 is preferably formed from silver foil which is flared out at the lower portion thereof to provide a flange 16 for contacting the scalp of a subject. The silver circular member 12 is chloridized so as to provide a silver chloride coating on the wall of the opening 14 which is the conductive element of the bioelectrode. An insulated wire 18 is connected to the element 12 for electrical connection to an electroencephalograph. An insulating coating 20 is provided on the outer surface of the element 12.

In accordance with the principal feature of the present invention, the bioelectrode is secured to the scalp 21 of a living subject without the use of cements, adhesives, paraffin or head frame, and furthermore without the requirement of shaving the scalp of the subject, by passing a portion 22 of the hair of the scalp through the opening 14 in the bioelectrode in a fashion as shown in FIG. 2. The hair is readily passed through the opening 14 by providing a slot 23 in the member 12 which extends from the Opening 14 to the edge of the insulation layer 20. By providing such a slot, the hair need not be threaded through the opening 14 but need only be passed laterally through the slot 23 into the opening 14 when positioning the bioelectrode on the scalp. After the bioelectrode is positioned on the scalp, electrolyte is inserted into the opening 14 to provide an electrolytic path between the silver chloride coating on the member 12 and the scalp. Thereafter, the hair passing through the opening 14 is tied into a knot 24 at the upper portion of the bioelectrode firmly securing the bioelectrode to the scalp.

FIG. 3 shows an additional form of the bioelectrode of the invention, generally designated by numeral 25, which has a similar configuration to the electrode shown in FIG. 1. The bioelectrode 25 includes a circular member 26 formed of a non-conductive material such as plastic having essentially the same configuration as the member 12 in FIG. 1. An electrode component 28, such as a silversilver chloride pellet as described in US. Patent No. 3,111,478 is mounted on the wall of the opening 30 in the member 26. An insulated wire 32 is connected to the electrode component 28 by any suitable means and passes outwardly through the nonconductive member 26 for connection to an external circuit. As seen in FIG. 3, the electrode component 28 is mounted remote from the bottom flanged end 34 of the bioelectrode so that motion artifacts are minimized. The bioelectrode 25 has a vetrical slot therein, not shown, similar to the slot 23 in FIG. 1 so that it may be attached to the scalp of a subject in the same manner as described above in connection with bioelectrode 10.

An additional form of bioelectrode of the invention is illustrated in FIGS. 4 and 5 and generally designated by numeral 36. This bioelectrode comprises a circular member or ring 38 and a cap 40. The ring 38 has a central opening 42 therethrough and a slot 44 extending from the opening to the outer edge of the ring 38. The ring 38 is preferably formed of silver which has been chloridized to form a surface coating of silver chloride thus constituting the conductive element of the bioelectrode. The cap 40 is formed of an insulating material such as plastic and has a projection 46 which, as best seen in FIG. 5, has a length less than the height of the ring 38 so as to provide 'a portion of the opening 42 open to form a reservoir for receiving electrolyte. The projection 46 has a diameter essentially the same as that of the opening 42 so as to establish a friction fit between the two elements when assembled together. An insulated wire 48 is suitably attached to the ring 38 for connecting the ring to an external circuit.

In attaching the bioelectrode 36 to the scalp 21 of a subject, a portion of the hair of the subject is passed through the slot 44 into the passage 42 and laid across the upper annular surface or end 50 of the bioelectrode as best seen in FIG. 6. The passage 42 is then partially filled with an electrolyte. Thereafter, the cap 40 is frictionally engaged into the opening 42 of the ring 38 so as to clamp the hair passing through the passage 42 securely thereby firmly securing the bioelectrode to the scalp of the subject.

While the bioelectrode 36 is shown as employing a ring 38 formed entirely of the conductive material, it is understood that the ring 38 could be formed of a nonconductive material with an electrode component such as the component 28 illustrated in FIG. 3 mounted in the opening 42. Also, the metallic ring 38 of the bioelectrode 36 may be coated with an insulating layer except on the wall of the opening 42.

A bioelectrode 56 is illustrated in FIG. 7 having the same configuration as the bioelectrode 36 except that the ring member 38 is formed entirely of an insulating material and an electrode component 60 is mounted in the cap 62 so as to be exposed to electrolyte in the passage 64 in the ring '58. An insulated wire 66 is connected to the electrode component 60 and extends through the cap 62 for connection to an external circuit. The ring 58 has a vertical slot therethrough, not shown, to facilitate the passing of hair on the scalp through the passage 64 so as to secure the ring 58 to the scalp of a subject in the manner described above in connection with bioelectrode 36.

According to another feature of the invention, one or more hairs are pulled from the scalp of the subject at the point where the electrolyte reservoir of the bioelectrode overlies the scalp. This permits electrolyte to fill the root cavity which results in the source impedance being substantially reduced. When employing a bioelectrode of the type disclosed herein, a hair which passes through the opening in the bioelectrode is pulled out of the scalp either before or after filling the electrolyte reservoir with electrolyte. It has been found that by this method the source impedance is reduced, thereby improving the performance of the bioelectrode. Although several embodiments of the invention have been disclosed herein for purposes of illustration, it will be understood that various changes can be made in the form, details, arrangements and proportions of the various parts in such embodiments without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. A bioelectrode for attachment to the scalp of a subject without removing hair from the scalp comprising:

a circular member having a central opening therethrough with an annular end of said member being adapted to physically contact the scalp;

at least a portion of the wall of said opening being conductive and said opening being capable of containing an electrolyte for providing an electrolytic path between said conductive portion and the scalp; said member having a slot extending from said opening to the outer edge of said member whereby hair on .4 the scalp may be passed through said slot to said opening when said annular end of said member contacts the scalp;

lead wire means attached to said conductive portion for connection to an external circuit; and

securing means replaceably mounted on said circular member for rapidly and firmly securing hair passing through said central opening to said member.

2. A bioelectrode as set forth in claim 1 wherein said securing means comprises a cap frictionally engaging the other annular end of said circular member.

3. A bioelectrode for attachment to the scalp of a subect without removing hair from the scalp comprising:

a circular member formed of silver having a central opening therethrough with an annular end of said member being adapted to physically contact the scalp;

the wall of said central opening having a coating of silver chloride thereon and said opening being capable of containing an electrolyte for providing an electrolytic path between said silver chloride coating and the scalp;

said member having a slot extending from said opening to the outer edge of said member whereby hair on the scalp may be passed through said slot to said opening when said annular end of said member contacts the scalp; and

lead wire means attached to said circular member for connection to an external circuit.

4. A bioelectrode for attachment to the scalp of a subject without removing hair from the scalp comprising:

a circular member formed of nonconductive material having a central opening therethrough for containing an electrolyte with an annular end of said member being adapted to physically contact the scalp;

said member having a slot extending from said opening to the outer edge of said member whereby hair on the scalp may be passed through said slot to said opening when said annular end of said member contacts the scalp;

cap means frictionally engaging the other annular end of said member;

an electrode component mounted in said cap with a portion of said component being exposed to said opening in said member; and

lead wire means connected to said electrode component for connection to an external circuit.

5. A method of establishing conductive contact with the scalp of a subject without removing hair from the scalp comprising the steps of:

providing a circular member having an opening therethrough with at least a portion of the wall of said opening being conductive;

placing an end of said member in physical contact with said scalp with a portion of the hair on the scalp passing through the opening in said member;

filling said opening with an electrolyte; and

thereafter firmly securing said member to the hair passing through said opening.

6. A method as set forth in claim 5' wherein said member is secured to said hair by tying the hair in a knot at the other end of said member.

7. A method as set forth in claim 5 wherein said member is secured to said hair by frictionally engaging a cap on the other end of said member with the hair positioned between said cap and said other end.

8. A method of establishing conductive contact with the scalp of a subject without removing hair from the scalp comprising the steps of:

providing a circuit member formed of nonconductive material having an opening therethrough;

placing an end of said member in physical contact with said scalp with a portion of the hair on the scalp passing through the opening in said member and overlying the other end of said member;

filling said opening with an electrolyte;

providing a cap carrying an electrode component; and

frictionally engaging said cap on the other end of said member to clamp said hair therebetween with said electrode component contacting the electrolyte in said opening.

9. A method of establishing conductive contact with the skin of a subject comprising the steps of:

providing a bioelectrode comprising a body having a reservoir filled with electrolyte opening at one face of the body with a conductive member in said reservoir;

pulling at least one hair from the skin of the subject to reduce the source impedance; and

applying said bioelectrode to the skin with said reservoir overlying the point where said hair was removed.

References Cited UNITED STATES PATENTS 2,887,112 5/1959 Smith 128-417 3,157,181 11/1964 McCarty 128404 WILLIAM E. KAMM, Primary Examiner U.S. Cl. X.R. 128-417

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