Oxygen measuring electrode assembly

Claim 1

A polarographic electrode assembly for transcutaneous measurement of partial oxygen pressure in arterial blood, comprising: (a) an electrode part, including as an electrode unit: an anode having a ring-shaped working surface; cathode means constituting a cathode having working surface means constituting a working surface disposed within an imaginary circumscribing circle and perimetrically surrounded by said ring-shaped working surface of said anode, with radial spacing between said anode working surface and said cathode working surface means; and an electrode holder of insulative material, said electrode holder holding said anode and said cathode means, maintaining said radial spacing, and providing an electrically and thermally insulated relationship for said anode and said cathode means relative to one another; (b) a membrane holder part, including: an oxygen-permeable hydrophobic electrode membrane having an outer peripheral margin; and a cylindrical tubular membrane holder having an axially inner annular end face and an axially outer annular end face with a longitudinal bore extending between them; means fixedly circumferentially holding said outer peripheral margin of said electrode membrane on said axially inner end face of said cylindrical tubular membrane holder with a predetermined, circumferentially substantially uniform tension and with said electrode membrane extending across said longitudinal bore; and (c) a skin heating part, including: an integral, heating conducting metal block having a radially inner relatively thin disk-shaped portion and a radially outer, relatively thick annular peripheral portion, each of these portions having an axially outer side and an axially inner side, the two axially inner sides being substantially axially aligned so as to provide one substantially flat surface incorporating both of them, but the axially outer side of said relatively thin disk-shaped portion lying substantially axially inwardly of said axially outer side of said relatively thick annular peripheral portion, so as to provide an electrolyte well having said axially outer side of said relatively thin disk-shaped portion as its bottom and a radially inwardly facing generally cylindrical surface of said relatively thick annular peripheral portion as its sidewall; means providing a generally central hole axially through said relatively thin disk-shaped portion of said integral, heat conducting block, said through hole communicating with said well and being of a size and shape large enough to expose therethrough substantially all of said working surface means of said cathode means when said electrode unit is telescopically axially received in said well; said substantially flat surface being adapted to be presented in confronting relation to the skin of a subject who is to be monitored, said substantially flat surface being larger in area than said through hole; and an electric heater and a temperature-detecting element, both being mounted on said skin heating part so as to form a unitary subassembly therewith; said electrode unit being axially telescopically removably received in the bore of said membrane holder part and both said electrode unit and said membrane holder part being axially telescopically removably received in said well of said skin heating part, with both said anode working surface and said cathode working surface means closely confronting said electrode membrane; said electrode membrane extending across said through hole to provide a portion thereof axially exposed through said through hole and having said cathode working surface means in operable relationship therewith.