Stretchable electrode and method of making physiologic measurements

Abstract

A stretchable electrode for use in physiologic measurements on a human body, such as peripheral impedance plethysmography, is disclosed. One embodiment of the stretchable electrode comprises an uninsulated stainless steel wire braid formed into a tubular conductor surrounding an elastic core and attached to an elastic substrate or base. Other embodiments of the stretchable electrode include a garter spring, a flat braided or woven conductor and an undulating wire. The electrode may be placed about a limb of a human body and elastically stretched so that the conductor is in substantially continuous circumferential electrical contact with the skin of the limb. A method of attaching the stretchable electrode to the limb of a human body is also disclosed.

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         6 . An electrode for making electrical contact with the skin comprising an uninsulated metal conductor adapted to make electrical contact with the skin, said conductor having a longitudinal axis and being elastically stretchable along said axis, wherein said metal conductor is a garter spring. 
     
     
         7 . An electrode for making electrical contact with the skin comprising an uninsulated metal conductor adapted to make electrical contact with the skin, said conductor having a longitudinal axis and being elastically stretchable along said axis, wherein said metal conductor comprises an undulating wire. 
     
     
         8 . An electrode for making electrical contact with the skin comprising an uninsulated metal conductor adapted to make electrical contact with the skin, said conductor having a longitudinal axis and being elastically stretchable along said axis, wherein said metal conductor is a substantially flat band formed of braided or woven wires attached to an elastic substrate. 
     
     
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         17 . A stretchable electrode adapted for encircling a body portion of a subject and making substantially continuous circumferential electrical contact with the skin of the body portion, comprising an uninsulated metal conductor having a longitudinal axis, said conductor being elastically stretchable along said axis, wherein said metal conductor comprises a stainless steel garter spring. 
     
     
         18 . A stretchable electrode adapted for encircling a body portion of a subject and making substantially continuous circumferential electrical contact with the skin of the body portion, comprising an uninsulated metal conductor having a longitudinal axis, said conductor being elastically stretchable along said axis, wherein said metal conductor is a substantially flat band formed of braided or woven wires attached to an elastic substrate. 
     
     
         19 . A stretchable electrode adapted for encircling a body portion of a subject and making substantially continuous circumferential electrical contact with the skin of the body portion, comprising an uninsulated metal conductor having a longitudinal axis, said conductor being elastically stretchable along said axis, wherein said metal conductor is made of a stainless steel wire braid formed into a tube surrounding an elastic core and means connected to said conductor for fastening said electrode about the body portion with the metal conductor in its elastically stretched condition, and wherein said band is disposed between two layers of a conductive adhesive hydrogel. 
     
     
         20 . A stretchable electrode adapted for encircling a body portion of a subject and making substantially continuous circumferential electrical contact with the skin of the body portion, comprising an uninsulated metal conductor having a longitudinal axis, said conductor being elastically stretchable along said axis, wherein said metal conductor is made of a stainless steel wire braid formed into a tube surrounding an elastic core and means connected to said conductor for fastening said electrode about the body portion with the metal conductor in its elastically stretched condition, and wherein said band is embedded in a sheet of conductive adhesive hydrogel. 
     
     
         21 . A stretchable electrode adapted for encircling a body portion of a subject and making substantially continuous circumferential electrical contact with the skin of the body portion, comprising an uninsulated metal conductor having a longitudinal axis, said conductor being elastically stretchable along said axis, wherein said metal conductor comprises an undulating wire. 
     
     
         22 . The electrode of  claim 21 , wherein said undulating wire is disposed between two layers of a conductive adhesive hydrogel. 
     
     
         23 . The electrode of  claim 21 , wherein said undulating wire is embedded in a sheet of conductive adhesive hydrogel. 
     
     
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         27 . An electrode for making physiologic measurements of the human body comprising an uninsulated metal wire formed into an undulating shape about an undulation axis so as to be elastically stretchable in a plane containing said axis, and means for attaching the undulating metal wire to a portion of the body in an elastically stretched condition with the uninsulated wire in substantially continuous electrical contact with the skin of the body portion. 
     
     
         28 . The electrode of  claim 27 , wherein said undulating metal wire is made of stainless steel and said attaching means comprises a moisture impervious substrate to which the undulating metal wire is fastened. 
     
     
         29 . The electrode of  claim 27 , wherein said undulating metal wire is embedded in or between one or more layers of an elastic, electrically conductive adhesive hydrogel. 
     
     
         30 . The electrode of  claim 27 , including four of said uninsulated undulating wires arranged in parallel on said attaching means in a quadripolar array for making peripheral plethysmograph measurements, said attaching means fastening said wires and substrate about a limb of the body with the wires in an elastically stretched condition. 
     
     
         31 . A method of attaching a conductive electrode about a limb of a human body comprising the steps of:
 providing an elastically stretchable conductor having an axial length and two ends;   placing the conductor circumferentially about the limb with the ends thereof in overlapping relation;   elastically stretching the conductor so that the conductor is in substantially continuous circumferential electrical contact with the skin of the limb; and   fastening the conductor about the limb with the conductor in an elastically stretched condition.   
     
     
         32 . The method of  claim 31 , comprising the further step of moistening the conductor prior to placing the conductor about the limb.