Conductive adhesive medical electrode assemblies

• US 4,706,680 A
• Filed: 06/30/1986
• Issued: 11/17/1987
• Est. Priority Date: 06/30/1986
• Status: Expired due to Term

• Current Assignee: Nepera, Inc.
• Original Assignee: Nepera, Inc.
• Inventors: Keusch, Preston, Essmyer, John L.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US06/879,877
• Time in Patent Office: 505 Days
• Field of Search: 128/639-641, 128/798, 128/802, 128/803, 604/20, 604/290, 252/500
• US Class Current: 600/392
• CPC Class Codes: A61B 2018/00107 Coatings on the energy applicator
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/259 using conductive adhesive means, e.g. gels
• CPC Class Codes: A61B 5/266 containing electrolytes, conductive gels or pastes
• CPC Class Codes: A61B 5/274 using snap or button fasteners
• CPC Class Codes: A61B 5/28 for electrocardiography [ECG]

Abstract

A medical electrode adapted for providing electrical contact with a patient'"'"'s skin and comprising:

(a) a conductive member including means for connecting the medical electrode to an external electrical apparatus; and

(b) interfacing means comprising a solid sheet of a conductive viscoelastic hydrophilic gel which is a homogeneous aqueous mixture, substantially free of unbound water, monomers and cross-linking agents, consisting essentially of

(i) water;

(ii) an amount dissolved in the water of a water soluble electrolyte effective to reduce the transverse electrical resistance of the sheet to an impedance at 60 Hz of less than 1,000 ohms; and

(iii) an amount dispersed uniformly throughout the water of from about 2 to 35 wt % of a cross-linked polyethylene oxide, effective to form with the water a tacky surface viscoelastic adhesive solid;

which hydrophilic gel is produced by subjecting a liquid film of an aqueous solution having a viscosity of about 2-2,000×10³ cps of the electrolyte and a linear water soluble polyethylene oxide having a weight average molecular weight from about 0.05-10×10⁶ Daltons to an amount of high energy radiation effective to convert the liquid film to a sheet of adhesive viscoelastic solid.

Claims

1. In a medical electrode adapted for providing electrical contact with a patient'"'"'s skin and comprising:

(a) a conductive member including means for connecting the medical electrode to an external electrical apparatus; and

(b) interfacing means comprising a solid sheet of a conductive viscolastic hydrophilic gel, connected electrially with the conductive member and having a face adapted for interfacing electrically with and adhesively to the patient'"'"'s skin, which sheet is more cohesive than it is adhesive to the patient'"'"'s skin and is mechanically connected more firmly to the conductive member than it can be adhesively affixed to the patient'"'"'s skin, thereby enabling concurrent removal of the conductive member and the sheet from the skin after use without leaving a noticeable residue on the skin,

the improvement wherein the hydrophilic gel is a homogeneous aqueous mixture, substantially free of unbound water, monomers and cross-linking agents, consisting essentially of

(i) water;

(ii) an amount dissolved in the water of a water soluble electrolyte effective to reduce the transverse electrical resistance of the sheet to an impedence at 60 Hz of less than 1,000 ohms, and

(iii) an amount dispersed uniformly throughout the water of from about 2 to 35 wt % of a cross-linked polyethylene oxide, effective to form with the water a tacky surfaced viscoelastic solid,

which hydrophilic gel is produced by subjecting a liquid film of an aqueous solution, having a viscosity of about 2-2,000×

10³ cps, of the electrolyte and a linear water soluble polyethylene oxide having a weight average molecular weight from about 0.05-10×

10⁶ Daltons to an amount of high energy radiation effective to convert the liquid film to a sheet of the viscoelastic solid having an adhesive face which in the rolling ball tack test gives a rolling ball distance of less than about 10 mm and an adhesion energy force in the Adhesion Energy Density Determination Test of about 2 to 80 g-cm/cm² which adhesive sheets have greater cohesive strength than adhesive strength, whereby the sheet can be removed from a surface to which it is affixed without leaving a visible residue.

2. An electrode according to claim 1, wherein the hydrophilic gel contains immersed therein a low area-weight scrim.

3. An electrode according to claim 2, wherein the scrim is a sheet of non-woven polyethylene.

4. An electrode according to claim 1, wherein the electrolyte is a water soluble salt present in a concentration of about 0.1 to 15 wt %.

5. An electrode according to claim 4, wherein the water soluble salt is potassium chloride or sodium chloride.

6. An electrode according to claim 1, wherein the concentration of the polyethylene oxide in the hydrophilic gel is about 4 to 25 wt %.

7. An electrode according to claim 1, wherein the concentration of the polyethylene oxide in the hydrophilic gel is about 7 to 12 wt %.

8. An electrode according to claim 1, wherein the linear polyethylene oxide has a molecular weight of about 0.2 to 6×

10⁶ Daltons.

9. An electrode according to claim 1, wherein the face of the sheet adapted for interfacing with the patient'"'"'s skin is covered by a backing sheet which is peelably removable therefrom.

10. An electrode according to claim 1, wherein the hydrophilic gel contains immersed therein a low area-weight scrim;

wherein the electrolyte is a water soluble salt present in a concentration of about 0.1 to 15 wt %. wherein the linear polyethylene oxide has a molecular weight of about 0.5 to 5×

10⁶ Daltons and is present in the hydrogel at a concentration of about 4 to 25%; and

wherein the face of the sheet adapted for interfacing with the patient'"'"'s skin is covered by a backing sheet which is peelably removable therefrom.

11. An electrode according to claim 10, wherein the scrim is formed of a sheet of non-woven polyethylene and wherein the water soluble salt is potassium chloride or sodium chloride.