Surgery – Truss – Pad
Patent
1991-01-28
1993-02-02
Cohen, Lee S.
Surgery
Truss
Pad
128639, 29825, 29874, A61B 5402
Patent
active
051830434
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a low resistance electrical pickup--more particularly--but not exclusively--for use in a fetal scalp electrode or other biosensing electrode, and the manufacture thereof.
SUMMARY OF THE INVENTION
According to the present invention, a method of manufacture of a low resistance electrical pick-up is characterised by applying to a length of stainless steel wire a first coating layer of nickel, and a subsequent coating layer of silver, optionally with an intervening layer of copper, an area of the silver layer then being chloridized and coated with bio-compatible plastics material, e.g., TECOFLEX.RTM., a bio-compatible polyurethane resin. A further length or lengths of non-chloridized silver layer may be coated with a non-conducting varnish.
In a particular application of the invention to a fetal scalp electrode or other biosensing electrode of the type having an arcuate needle of stainless steel--which may serve as a reference electrode and/or measuring electrode and/or introducer for a separate electrode--the arcuate needle is plated with nickel and then silver, optionally with an intervening layer of copper, and an area of the silver layer at least on the outside of the curve of the needle, and possibly spaced from the point of the needle, is chloridized and then coated with bio-compatible plastics, and the remainder of the silver layer is coated with a non-conducting varnish.
The coating of the chloridized silver area can be given a thin coating of TECOFLEX by dipping it into a solution of TECOFLEX in tetrahydrofuran (THF) which is allowed to set (approximately 12 to 24 hours) before the remaining areas of the electrode are painted with a non-conducting varnish .
BRIEF DESCRIPTION OF THE DRAWINGS
A number of embodiments of the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings, in which:
FIG. 1 is a fragmentary enlarged side elevation of a basic low resistance electrical pick-up manufactured in accordance with the invention;
FIG. 2 is an even greater enlarged cross-section on the line II--II of FIG. 1;
FIG. 3 corresponds to FIG. 2 but includes a slight modification;
FIG. 4 is a greatly enlarged skeletal perspective view of the head member of a "Surgicraft-Copeland" fetal scalp electrode (FSE) including a low resistance electrical pick-up manufactured in accordance with the invention;
FIG. 5 is a fragmentary ECG trace obtained using a FSE as in FIG. 4; and
FIG. 6 is a fragmentary ECG trace obtained with an un-modified "Surgicraft-Copeland" FSE for comparison with the trace of FIG. 5, the paper speed in FIG. 5 being twice that in FIG. 6.
The thickness of the coating layers in FIGS. 1 to 3 have been greatly exaggerated, even compared to the enlarged scale, for the sake of clarity.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
In FIGS. 1 and 2, a low resistance electrical pick-up comprises a length of stainless steel wire 10 having a first coating layer 14 of nickel, and a subsequent coating layer 15 of silver, an area (or length) 11 of the silver layer being chloridised (indicated in FIG. 1 by the thicker broken line) and then coated with bio-compatible plastics material 12, e.g., TECOFLEX. Further lengths 13 of non-chloridized silver layer 15, and preferably also adjacent exposed lengths of the nickel layer 14 and stainless steel wire 10 may be coated with a non-conducting varnish.
FIG. 3 corresponds closely to FIG. 2 but indicates a layer 16 of copper between the nickel layer 14 and the silver layer 15.
In FIG. 4, the head member 17 of a "Surgicraft-Copeland" FSE, as described in GB-PS 1 316 072 or GB-PS 1 523 263 (or U.S. Pat. No. 4,151,835), has an arcuate needle 18 formed on the outer end of a radial arm 19 from a main stainless steel wire 10, the arcuate needle 18 being plated with nickel 14 and then silver 15 (optionally with an intervening copper layer, not shown, but refer to FIG. 3), an area (not shown) of the silver layer at least on the outside of the curve of the needl
REFERENCES:
patent: 3568662 (1971-03-01), Everett
patent: 3989038 (1976-11-01), Neward
patent: 4685466 (1987-08-01), Rau
Hon, "A Fetal Electrocardigraph Electrode", The Yale Journal of Biology and Medicine, vol. 39, No. 1, Aug. 1966, pp. 54-58.
Hon et al., "Electronic Evaluation of Fetal Heart Rate", Obstetrics and Gynecology, vol. 40, No. 3, Sep. 1972, pp. 362-365.
Hon, "Instrumentation . . . Fetal Electrocardiography" Obsetrics and Gynecology, vol. 30, No. 2, Aug. 1967, pp. 281-286.
Band David M.
Penman David G.
Cohen Lee S.
Surgicraft Limited
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