Conductive adhesive medical electrode assemblies

Claim 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 2-2,000×10 3 cps, of the electrolyte and a linear water soluble polyethylene oxide having a weight average molecular weight from about 0.05-10×10 6 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/cm 2 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.