US3696807A - Medical electrode with relatively rigid electrolyte cup - Google Patents

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Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/25—Bioelectric electrodes therefor
  • A61B5/251—Means for maintaining electrode contact with the body
  • A61B5/257—Means for maintaining electrode contact with the body using adhesive means, e.g. adhesive pads or tapes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/25—Bioelectric electrodes therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
  • A61B2562/0209—Special features of electrodes classified in A61B5/24, A61B5/25, A61B5/283, A61B5/291, A61B5/296, A61B5/053
  • A61B2562/0217—Electrolyte containing

Definitions

• the electrode of this invention is designed for use with commercially available electrolytes in the form of electrode pastes or gels. It is known that the conductor portions of such electrodes should be spaced from the skin of the subject by the electrolyte to obtain the least resistance and to minimize motion artifacts or noise.
• Electrodes have been made with barriers to prevent contact between the skin and their conductor portions.
• the barriers are provided with small apertures to be filled with an electrolyte. Although such devices may minimize artifacts, they are difficult and thus costly to construct, and the imposition of the apertured barrier undesirably reduces conduction between the skin and the conductor portion of the electrode.
• Electrodes have been made without any barrier between the skin and the electrode conductor. For the most part these have been designed to provide electrical contact with only a very small skin area.
• One type of electrode provides for contact over a relatively large skin area.
• these electrodes have a relatively high profile, that is, a large height to diameter ratio.
• low profile electrodes are preferred to minimize the possibility of movement of the electrolyte, which may cause spurious signals, and to minimize the inconvenience experienced by the subjects wearing the electrodes.
• the electrode of this invention is provided with a relatively rigid, non-conductive, low profile cup member having a convexly curved rim and placed in an inverted position on the skin of the subject.
• the cup member is effectively clamped to the skin by an overlying elastic sheet having a pressure sensitive adhesive surrounding the cup member.
• the elastic sheet When attached to the skin, the elastic sheet resiliently presses the cup member against the skin to firmly hold the cup member in a fixed position. Separation of the elastic sheet from the cup member is prevented by a clamp plate positioned on top of the sheet.
• the conductor portion of the electrode includes a thin conductive plate located in the cavity between the cup member and the skin, the conductive plate abutting the base of the cup member.
• the entire cup member can be filled with an electrolyte to provide a broad. area of contact over theskin.
• the conductor comprises a snap fastener member projecting through the cup member, the carrier sheet and the clamp plate to hold these parts in assembled relation.
• the clamp plate is preferably constructed identically to the cup member, both being similar to cavity washers. The confronting margins of the cup member and the clamp plate squeeze an annular projection of the elastic sheet thereby to assist in holding the center portion of the elastic sheet under tension when the lower surface of the elastic sheet is adhered to the skin.
• the elastic sheet is desirably a sponge like material, preferably open cell polyvinylchloride, because such material may be stretched in all directions and has an elastic character.
• open cell polyvinylchloride sheet or the like it is desired that both the upper and lower surfaces have a relatively closed cell construction.
• a partially closed cell construction is desired on the lower surface to better form a barrier layer for receiving a pressure sensitive adhesive.
• the top surface is preferably closed cell because closed cell surfaces do not retain dirt as readily as open cell material.
• the relatively closed cell surfaces also contribute to the elasticity of the sheet which is necessary to maintain the cup member pressed against the skin.
• a sheet made from open cell polyvinylchloride with partially closed cell upper and lower surfaces also has the advantages of being inexpensive, soft to the touch and pleasing in appearance. Air readily passes through such material to ventilate the skin.
• FIG. 1 is a perspective view of an electrode made in accordance with this invention shown applied to the hand of a subject;
• FIG. 2 is a cross sectional view of the electrode, taken along line 2-2 of FIG. 1, applied to the skin;
• FIG. 3 is an exploded perspective view of an electrode in accordance with this invention and a protective sheet for the adhesive prior to assembly of these parts;
• FIG. 4 is a cross sectional view of an electrode made in accordance with this invention with a different type of protective member.
• An electrode generally designated 10 made in accordance with this invention is shown secured to the hand H of a subject in FIGS. 1 and 2.
• the electrode 10 consists of a circular, elastic pad or sheet 12 overlying a centrally located, inverted cup member 14, a clamp plate l6 located on top of the sheet 12 in alignment with the inverted cup member 14, and a metallic conductor formed from a male snap fastener member, generally designated 18.
• the annular area of the lower surface of the sheet 12 in surrounding relation to the cup member 14 is provided with a pressure sensitive adhesive layer 20 for attachment of the electrode 10 to the skin.
• electrical signals from the skin are amplified and sensed by apparatus (not shown) connected to the snap fastener member 18 by a conductive lead and cooperating snap fastener member, shown by phantom lines 18a.
• the electrical path is from the skin through an electrolyte confined in a chamber or cavity 42 enclosed by the cup member 14 and the skin, and thence throughthe snap fastener member 18.
• the cup member 14 is in the form of a cavity washer and has a circular flat base 22 surrounded by an annular flange 24 which is semicircular or U-shaped in cross section.
• the center of the cup base 22 is apertured as indicated'at 26.
• the cup member 14 is electrically non-conductive and can be vacuum formed from a relatively thin sheet of a suitable thermoplastic. such as vinyl, linear polyethylene, cellulose acetate butyrate, or the like.
• the clamp plate 16 is also non-conductive and is preferably identically constructed to the cup member 14 and accordingly includes a circular flat base 28 .with a U-shapedrim or flange 30 and has a central aperture 32.
• the shape of the clampv plate 16 is not critical but the shape illustrated is preferred because of the savings in manufacturing costs resulting from use of the same parts for both the cu member 14 and the clamp plate 16.
• The. male snap fastener member .18 comprises a lower circular plate portion. 34 from the center of which a hollow, open ended stud 36 is formed upwardly, and an upper plate 'portion- 38 having an upwardly protruding, hollowsocket 40.
• the cup member 14 and the clamp plate 16 are first centrally located and aligned on opposite sides of the sheet 12.
• the stud 36 is then inserted throughthe aperture 26, pierced through the center of the sheet 12 and then through the aperture 32 into the socket 40.
• the parts of the snap fastener member 18 are then pressed together whereupen the upper end of the stud 36 folds inwardly and its side walls collapses outwardly, causing the fastener member parts to be tightly wedged together.
• the snap fastener 18 is metal and, as well known to those skilled in the art, preferably has a coating or plating of silver or the like composition .to provide a satisfactory electrical interface with the electrolyte confined in the cavity or chamber 42.
• the adhesive layer 20 may be applied .to the lower surface of the sheet 12 either before or after assembly. After the parts are assembled and the adhesive layer 20 applied, a protective waxed paper sheet 44 having a central cutout 46 forthe cup member 14is applied to the bottom of thesheet 12. The electrode with the protective sheet 44 may then be stored until ready for use.
• An alternative arrangement is shown in FIG. 4 wherein the cup member 14 is loaded with the electrolyte at the time of assembly and a suitably formed plastic or paper protective sheet 48 is applied in covering relation to both. the lower surface of the sheet 12 and the cup member 14 to retain the electrolyte therein.
• the protective sheet 44 or the protective sheet 48 are easily removable at the time the electrode 10 is to be used.
• the metallic snap fastener 18 which is the only conductor portion of the electrode 10, should be supported away from contact with the skin.
• the area between the snap fastener 18 and the skin should be completely filled with the electrolyte. Further, the movement of the electrode relative to the skin and the electrolyte should be positively restricted.
• the electrode 10 of this invention has an unusually low profile. These characteristics result primarily from the use of the elastic sheet 12 and the design of the cup member 14.
• the semicircular or- U-shaped flange 24 forms a convexly curved rim defining the mouth of the cup member 14 and an outer wall, designated 50, diverging outwardly from the rim.
• the upper margin of the outer wall 50 is substantially coplanar with 1 the upper surface of the base 26..
• the central portion of the elastic sheet is tightly compressed between the confronting base surfaces of the cup member 14 and the clamp plate 16. Accordingly, prior to attachment of the electrode 10 to the skin, the sheet'12 and its adhesive layer 20 are axially spaced above the rim of the cup member 14.
• the sheet 12 In order to attach the electrode 10 to theskin, .the sheet 12 must be flexed downwardly, whereupon the annular portion of the sheet 12 immediately surrounding the outer wall 50 is stretched to span the area between the upper, marginal edge of the diverging outer wall 50 and the portion of the skin to which the adhesive layer 20is secured. Because of its elastic nature, the stretched portion of the sheet 12 resiliently presses the convexly curved rim formed by the flange 24 into the skin, creating a slight depression therein. As a result, the cup member 14 is firmly retained in sealing relation to the skin, thereby positively confining the electrolyte within the cavity or chamber 42. Also, movement of the cup member 14 and the electrolyte relative to the skin is avoided.
• the U-shaped flange has a sufficient depth to create a minimal, but adequate spacing between the skin and the conductive lower plate34' of the snap fastener member 18 within the cavity 42. Because movements of the cup member 14 are restricted, the spacing between the plate portion 34 and the skin. is maintained over long periods of use.
• the elastic sheet 12 is preferably formed from a foamed or open cell polyvinylchloride havingrelatively closed cell upper and lower surfaces. This type of material can be obtained at a low cost, is sufficiently flexible to conform to the skin, and has sufficient elasticity to press the cup member 14 against the skin without tearing or pulling away from,
• the two surfaces of foamed polyvinylchloride sheets are typically of a slightly different nature, one having a more closed cell construction than the other. Although these surfaces are interchangeable in the manufacture of the electrode 10, it is presently preferred that the more open cell surface be lowermost.
• the more open cell surface is sufficiently porous to provide for adequate aeration or ventilation of the skin it covers, which is especially important for use over extended periods of time.
• the more closed cell surface is preferably uppermost because this type of surface is resistant to soiling.
• thermoplastic materials mentioned above for use in forming the cup member 14 and the clamp plate 16 are ideal for this purpose because they are inexpensive, non-conductive, and can easily be vacuum formed to the desired shape.
• a thermoplastic sheet is adequately rigid when formed to the illustrated cup shape to prevent collapse of the outer wall 50 under the force of the stretched sheet 12. The axial spacing of the rim and the upper margin of the cup member 14 are thus maintained.
• a thermoplastic sheet also has a resiliency which assists in forming a good seal with the parts of the snap fastener member 18. Accordingly, the electrolyte is retained entirely within the chamber 42 and the hollow center of the snap fastener member 18.
• both the cup member 14 and the clamp plate 16 are identically constructed of sheet material, the confronting margins of their outer walls compress the elastic sheet 12 therebetween, as indicated at 52. Therefore, substantially the only portion of the sheet 12 which is stretched when applied to. the skin is that portion between the outer wall 50 and the skin.
• the electrode had an overall height on the order of only 0.3 inch with the depth of the cup member 14 on the order of 0.094 inch and the elastic sheet 12 having a thickness of 0.125 inch.
• the diameter of the elastic sheet 12 was 2%. inch.
• the cup member 14, and accordingly the clamp member 16, had an overall diameter of 0.875 inch with the diameter of the base 22 being 95 inch.
• the lower snap fastener plate 34 had a diameter of 0.406 inch. These dimensions are not critical.
• the overall diameter of the cup membercould be between approximately 5% inch and one inch with corresponding variations in the diameter of the cup base 22 and the snap fastener plate 34. Unless the cup member 14 is made deeper, approximately 1 inch is deemed to be the maximum acceptable cup diameter because the skin bounded by the rim of a larger diameter cup member would likely engage the conductive plate portion 34.
• the adhesive layer 20 was applied to the lower surface of the elastic sheet 12 to form the adhesive layer 20. Because the lower surface of the elastic sheet 12 is not completely impervious, some of the adhesive may have migrated harmlessly beyond the partially closed cell surface. A sufficiently small quantity of the adhesive was applied to avoid closing the lower surface to the passage of air. Of course, the adhesive layer could be obtained in other ways. However, the adhesive layer should be pressure sensitive so that the elastic sheet 12 is stretched as a natural result of the pressing of the sheet 12 onto the skin. Also, the adhesive layer should not be of such a nature that it adversely affects the skinconforrning flexiblity of the elastic sheet or that it closes the pores of the lower surface of the elastic sheet 12;
• the diameter of the illustrated elastic sheet 12 is approximately two and one-half times the diameter of the cup member 14. It is preferred that the diameter of the carrier sheet 12 is on the order of two to three times the diameter of the cup member 14 to provide a broad skin contact area for the pressure sensitive adhesive layer 20. Because the carrier sheet 12 is flexible. it readily conforms to movements of the skin. Although the cup member 14 is relatively inflexible, it is sufficiently firmly held against the skin by the tension in the stretched portion of the carrier sheet 12 that the electrode of this invention can be used on subjects engaged in strenuous exercise.
• a medical electrode for attachment to the skin, means defining a collapse resistant cup for an electrolyte, said means including a U-shaped flange forming a convexly curved rim for engagement with the skin and an outer wall having a marginal edge axially spaced from said rim, an elastic sheet overlying said outer wall and having an adhesive on its lower surface adjacent said outer wall, means holding a portion of said sheet in engagement with said marginal edge of said outer wall whereby said sheet may be adhesively secured to the skin by stretching portions thereof immediately adjacent said outer wall, and whereby said stretched portions of said sheet resiliently press said outer wall and, accordingly, said rim into engagement with the skin.
• said means defining said cup comprises a thin sheet of plastic formed in the shape of a cavity washer.
• a medical electrode of the type having an inverted, non-conducting and collapse resistant cup member for containing an electrolyte and a conductor located within said cup member remote from its mouth
• the mouth of said cup member is defined by a U-shaped flange having a convvexly curved rim adapted to engage the skin of a subject, said flange having an outer wall with an upper margin spaced from said rim
• said electrode further includes an elastic sheet overlying and projecting beyond said upper margin, an adhesive on lower surface portions of said elastic sheet beyond said upper margin for attaching said elastic sheet to the skin, said outer wall supporting said elastic sheet remote from the skin whereby portions of said elastic sheet immediately adjacent said outer wall are stretched when said elastic sheet is moved into engagement with the skin, the stretched portions of said elastic sheet biasing said rim into firm engagement with the skin.
• said conductor consists of interfitting parts pressed together and having upper and lower plates engaging said clamp plate and said cup member, respectively, holding them in mutually fixed relation with said elastic sheet clamped therebetween.
• clamp plate is constructed identically to said cup member and wherein said clamp plate and said cup member are aligned on opposite sides of said elastic sheet.
• said elastic sheet is made from an open cell thermoplastic having relatively closed cell upper and lower surfaces.
• thermoplastic is polyvinylchloride
• a low profile non-conducting, relatively rigid, collapse resistant cup member having a base and a rim, apertured elastic sheet means connected to said cup member overlying said rim, an adhesive on the lower surface of said sheet means adjacent and in surrounding relation to said rim, a snap fastener projecting through said base and supported. by said base remote from said rim, said snap fastener projecting through an aperture in said sheet means, and a removable protective cover for said adhesive.

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• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Medical Informatics (AREA)
• Biophysics (AREA)
• Pathology (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Physics & Mathematics (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Electrotherapy Devices (AREA)

Abstract

Description

Claims (16)

Applications Claiming Priority (1)

Publications (1)

Family

ID=21749323

Family Applications (1)

Country Status (7)

Cited By (8)

Families Citing this family (3)

Citations (6)

Family Cites Families (3)

• 1970
  • 1970-02-13 US US11208A patent/US3696807A/en not_active Expired - Lifetime
• 1971
  • 1971-01-18 CA CA102,974A patent/CA989942A/en not_active Expired
  • 1971-02-10 DE DE2106124A patent/DE2106124C3/en not_active Expired
  • 1971-02-10 DE DE19717104831U patent/DE7104831U/en not_active Expired
  • 1971-02-12 FR FR7104825A patent/FR2078546A5/fr not_active Expired
  • 1971-04-19 GB GB2100271A patent/GB1324133A/en not_active Expired
• 1973
  • 1973-05-09 JP JP1973054480U patent/JPS5251751Y2/ja not_active Expired
• 1975
  • 1975-01-28 BE BE1006429A patent/BE824845Q/en not_active IP Right Cessation

Patent Citations (6)

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