Multipurpose medical stimulation electrode

• US 5,205,297 A
• Filed: 04/28/1989
• Issued: 04/27/1993
• Est. Priority Date: 03/25/1988
• Status: Expired due to Term

• Current Assignee: LecTec Corporation, Covidien AG (Medtronic Plc)
• Original Assignee: LecTec Corporation
• Inventors: Montecalvo, David A., Rolf, David
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Casler, Brian L.
• Application Number:
  US07/344,698
• Time in Patent Office: 1,460 Days
• Field of Search: 128/639-641, 128/798, 128/802-803, 604/20, 252/500, 522/79, 522/86, 522/152
• US Class Current: 607/152
• CPC Class Codes: A61B 8/4281 characterised by sound-transmitting media or devices for coupling the transducer to the tissue
• CPC Class Codes: A61N 1/0452 Specially adapted for transcutaneous muscle stimulation [TMS]
• CPC Class Codes: A61N 1/0456 Specially adapted for transcutaneous electrical nerve stimulation [TENS]
• CPC Class Codes: A61N 1/046 Specially adapted for shock therapy, e.g. defibrillation
• CPC Class Codes: A61N 1/048 Electrodes characterised by a specific connection between lead and electrode
• CPC Class Codes: A61N 1/0496 characterised by using specific chemical compositions, e.g. hydrogel compositions, adhesives

Abstract

A multipurpose medical stimulating electrode is described for use in external cardiac pacing, Transcutaneous Electrical Nerve Stimulation and neuromuscular stimulation which includes a protective cover layer at the top extending over and bonded to the upper surface of an electrically conductive layer, e.g. carbon filled silicone rubber having a resistivity of about 100 ohm centimeters on the lower surface of which is coated a selfsupporting skin contacting hydrogel layer comprising a matrix having a sticky surface adapted to make a good electrical contact with the skin and having a resistivity of greater than 1,000 and less than 10,000 ohm centimeters. The matrix is composed of natural or synthetic hydrocolloid, e.g. polyacrylamide, and/or natural gum such as karaya gum, water and a humectant comprising a polyhydric alcohol and optionally with Mg(OAc)₂ as a gelation inhibitor and electrolyte.

Claims

1. A multipurpose medical stimulating electrode comprising,

an electrically conductive backing having a resistivity on the order of about 1 to 1,000 ohm/square and an electrically conductive self-supporting hydrogel matrix coated thereupon, said matrix being adapted to make contact with the skin of a patient and being sufficiently flexible to conform to the contours of the body, said matrix comprising, a hydrophilic polymer, water in an amount of about 10% to 70% of the matrix and a humectant and said matrix

a) being substantially free of acid or of a salt of a strong acid,

b) having a resistivity greater than the resistivity of the backing and

c) having a resistivity between about 2,000 and 10,000 ohm-centimeters to thereby reduce current concentration i localized areas and prevent a runaway condition wherein a disproportionate amount of current passes through a localized area of the skin of the patient where electrical resistance has declined for inhibiting the perception of pain by the patient and the matrix has uniformly distributed therein a gelation inhibitor in an amount sufficient to inhibit gelation of the matrix prior to forming the matrix into a coating layer.

2. The electrode of claim 1 wherein the gelation inhibitor comprises Mg(OAc)₂.

3. A multipurpose medical stimulation electrode for external use in contact with the skin of a patient for carrying out cardiac pacing, neuromuscular stimulation, or transcutaneous electrical stimulation comprising, an electrically conductive flexible backing, an electrically conductive pin socket in conductive relationship with the backing and extending upwardly therefrom, said pin socket having a pin receptor opening therein for establishing electrical connection between the electrode and a flexible conductor having an electrically conductive terminal constructed and arranged to slide into the pin receptor opening, a self-supporting nonfluid hydrogel matrix connected to the backing and having an exposed surface adapted to directly contact the skin of the patient and to conform to the body contours, said hydrogel comprising a hydrophilic polymer hydrated with water and a humectant and a minor amount of an ionizable gelation inhibitor in an amount sufficient to reduce the viscosity of the gel to prevent premature gelation thereof during coating of the matrix onto a support in forming said electrode, said ionizable gelation inhibitor also contributing to the electrical conductivity of the matrix and said matrix

a) being substantially free of acid or of a salt of a strong acid,

b) having a resistivity greater than the resistivity of the backing and

c) having a resistivity between about 2,000 and 6,000 ohm-centimeters to prevent current buildup through specific localized portions of the matrix, thereby avoiding a runaway condition of high current flow in localized areas of the skin for inhibiting the sensation of pain by the patient.

4. The electrode of claim 3 wherein a pressure-sensitive adhesive layer is provided to extend around the periphery of the matrix to bond the electrode to the skin and to seal the hydrogel matrix from the atmosphere on all sides.

5. The electrode of claim 3 wherein the matrix comprises a synthetic hydrocolloid comprising polyacrylamide in the amount by weight of between about 10% to about 40% water, at least one humectant in the amount by weight of about 10% to about 50%, and the gelation inhibitor is Mg(OAc)₂ in the amount by weight of about 1% to about 12%.

6. The electrode of claim 3 wherein the electrode comprises by weight about 10% to 40% of a natural hydrocolloid gum, about 10% to 40% by weight of polyacrylamide, an adhesive comprising vinyl acetate in the amount by weight of about 1% to 10%.

7. The electrode of claim 3 wherein the electrically conductive backing comprises a conductive silicone rubber layer having a resistivity between about 1 and 1,000 ohms/square, said pin socket comprises an integral upwardly extending projection on the upper surface of the rubber layer and said pin socket has a horizontally disposed opening therein to define said pin receptor.

8. The electrode of claim 3 wherein the matrix contains karaya gum dispersed uniformly therein in the amount of from about 10% to 40% by weight of the matrix.

9. The electrode of claim 5 in combination with a flexible electrical conductor having a male pin-style terminal at one end and a selected one of a plurality of different terminals at the other end, said pin receptor opening of the pin socket receiving said male pin-style terminal and each of said different terminals at the other end of the flexible connector being interfaced with an electrical stimulator.

10. The electrode product of claim 3 wherein said matrix is manufactured by a process characterized by coating said matrix upon a sheet of flexible supporting material while said matrix is in a chilled condition.

11. The electrode product of claim 10 wherein said matrix is manufactured by a process characterized by chilling the matrix to between about -25°

C. and 20°

C. prior to being coated onto the supporting material.

12. A multipurpose medical stimulating electrode comprising,

an electrically conductive backing having a resistivity on the order of about 1 to 1,000 ohm/square and an electrically conductive self-supporting hydrogel matrix coated thereupon, said matrix being adapted to make contact with the skin of a patient and being sufficiently flexible to conform to the contours of the body, said matrix comprising, a hydrophilic polymer, water in an amount of about 10% to 70% of the matrix and a humectant and said matrix

a) being substantially free of acid or of a salt of a strong acid,

b) having a resistivity greater than the resistivity of the backing and

c) having a resistivity between about 2,000 and 10,000 ohm-centimeters to thereby reduce current concentration in localized areas and prevent a run-away condition wherein a disproportionate amount of current passes through a localized area of the skin of the patient where electrical resistance has declined for inhibiting the perception of pain by the patient and Mg(OAC)₂ is present in an amount sufficient to prevent premature gelation of the matrix prior to coating the matrix onto the electrically conductive backing.