GB2042898A

GB2042898A - Foetal Scalp Electrode

Info

Publication number: GB2042898A
Application number: GB7907143A
Authority: GB
Original assignee: AW Showell Surgicraft Ltd
Current assignee: AW Showell Surgicraft Ltd
Priority date: 1979-02-28
Filing date: 1979-02-28
Publication date: 1980-10-01
Also published as: GB2042898B

Abstract

A foetal scalp electrode of the type described in British Patents Nos. 1 316 072 and 1 523 263 is also provided with a capability for percentage oxygen determinations by providing an additional electrically conductive electrode wire 19 which passes between the radial arm 11 and the normally adjacent side of the cavity 9 (Fig. 5) to an additional hole 21 between the cavity and the outside of the head member 2, and an electrically conductive pin 22 is provided on the end of the wire 19 and projects from the hole 21 in the head member. The wire 19 may be a wire with an insulating coating except at its ends, one of which forms the pin 22, and the other of which makes contact with an additional terminal 20 (Fig. 7) in the electrical connector 1. The wire 19 may be disposed between the insulating sheath 8 and the helical spring 3 along the length between the connector 1 and the head member 2. Radial arm 11 presses on wire 19 to force pin 22 to project out from head 2. <IMAGE>

Description

SPECIFICATION Foetal Scalp Electrode This invention relates to foetal scalp electrodes of the type described in British Patents Nos., 1,316,072 and 1,523,263 and comprising an electrical connector, a head member of electrically insulating material, an electrically conductive helical spring with a terminal at one end in the electrical connector and with the other end secured to the head member, and an electrically conductive wire with a terminal at one end in the electrical connector, the wire extending through an insulating sheath inside the helical spring, and the other end of the wire being in a cavity in the head member and provided with an electrically conductive arcuate needle on an electrically conductive arm radial to the wire, with the arcuate needle normally urged, by torsion in the helical spring, through a hole between the cavity and the outside of the head member, and with the point of the needle looping back to the head member.

Such a foetal scalp electrode is used for ECG (electrocardiogram) determinations, and the object of the present invention is to provide such an electrode that is also capable of use for percentage oxygen determinations.

According to the present invention, a foetal scalp electrode of the type described above is provided with an additional electrically conductive electrode wire with a terminal at one end in the electrical connector (additional to the terminal already referred to), the additional electrode wire being insulated where it extends parallel to the wire with the radial arm and arcuate needle and into the cavity in the head member, the insulated additional electrode wire also passing between the radial arm and the normally adjacent side of the cavity to an additional hole between the cavity and the outside of the head member adjacent to the hole for the arcuate needle, and an electrically conductive pin is provided on the end of the additional electrode wire and projects from the additional hole in the head member.

The arcuate needle being normally urged, by torsion in the helical spring, through its hole in the head member and with the point of the needle looping back to the head member, the radial arm presses on the insulated additional electrode wire closely adjacent to the electrically conductive pin, which is thus forced to project from the additional hole in the head member, to ensure insertion of the pin into scalp with which the electrode is engaged by the arcuate needle.

Thus, the additional electrode wire may be a wire with an insulating coating except at its ends, one of which forms the electrically conductive pin, and the other of which makes contact with the respective terminal in the electrical connector.

The additional electrode wire may be disposed between the insulating sheath and the helical spring along the length between the connecting member and the head member.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a general view of a foetal scalp electrode in accordance with the invention; Figure 2 is a fragmentary elevation showing the other side of the head member of the electrode of Figure 1; Figure 3 corresponds to Figure 2 but shows the head member with the arcuate needle withdrawn into it; Figure 4 is an enlarged fragmentary section taken from the line 4-4 of Figure 2; Figure 5 is a section on the line 5-5 of Figure 4; Figure 6 corresponds to Figure 5 but shows the arcuate needle of the electrode withdrawn into the head member; and Figure 7 is an enlarged fragmentary section taken from the line 7-7 of Figure 1.

The foetal scalp electrode shown in the drawings comprises an electrical connector 1, a head member 2 of electrically insulating material (e.g. nylon), an outer electrically conductive wire in the form of a helical spring 3, with a terminal 4 in the electrical connector constituted by a straightened end portion of the spring, and with another straightened end 5 secured to the head member, and a central electrically conductive wire 6 with a terminal 7 at one end in the electrical connector, the central wire extending through an insulating sheath 8 (e.g. of polytetrafluoroethylene, so as to be selflubricating) inside the helical spring 3, and the other end of the wire being in a cavity 9 in the head member and provided with an electrically conductive arcuate needle 10 on an electrically conductive arm 11 radial to the wire 6, with the arcuate needle normally urged, by torsion in the helical spring out of the cavity through a hole 12 between the cavity and a flat surface 13 on the outside of the head member 2, and with the point of the needle looping back into the head member through à second hole 14 provided between the cavity 9 and the flat surface 13 for the point of the needle to enter, to afford greater secureness when in use (as will be described presently) and shielding of the point when not in use.

The outside of the head member 2 is also provided with a concave surface 15 facing oppositely to the flat surface 13, and the concave surface is formed with ribs 16 extending transversely with respect to the axis of the helical spring 3, which ribs deter a finger engaged therewith from sliding along the head member in a direction away from the electrical connector 1 when the adjacent fingers engage the sides 17 of the head member.

The helical spring 3 is covered with insulating material 18 over most of its length, to prevent abrasion, the exposed portion of the helical spring, for making contact with the mother, being adjacent the head member 2.

An additional electrically conductive electrode wire 19 with a terminal 20 at one end in the electrical connector 1 is insulated (by a fine coating of electrically insulating material which is not visible) where it extends parallel to the wire 6 and into the cavity 9 in the head member 2, the insulated wire 19 also passing between the radial arm 11 and the normally adjacent side of the cavity (see Figures 4 and 5) to an additional hole 21 between the cavity and the outside 13 of the head member 2 between the holes 12, 14 for the arcuate needle, and an electrically conductive pin 22 (formed by a bared end of the wire 19) projects from the hole 21. The additional electrode wire 19 is disposed between the insulating sheath 8 and the helical spring 3 along the length between the connecting member 1 and the head member 2.

The connector 1, (see Figure 7) comprises a two-part body of electrically insulating material (e.g. nylon), with a spigot 23 on one body part 24 and a socket 25 in the other body part 26 for coupling the body parts together, and with three holes 27 in the body part 24 for passage of the wire terminals 4, 7 and 20, which are electrically joined to insulated leads 28 passing through an axial hole in the body part 26 by means of pins 30 pressed into the holes 27 before fitting and sealing together of the body parts. The pins 30 are preferably gold-plated, so as to ensure excellent electrical joints, and the pins are tubular, to enable bared ends 31 of the leads 28 to be led through them and bent back before insertion into the holes containing the wire terminals.Relative rotation of the body parts 24,26 is prevented, whilst sealing of them together is being effected, by means of a projection 32 on the body part 24 engaged with a notch 33 in the body part 26. Ribs 34 extending longitudinally of the body parts of the connector 1 assist in gaining a good grip. The other ends 35 of the leads 28 are bared, to enable the electrical connector 1 to be connected to monitoring equipment (not shown).

With the head member 2 of the electrode held, by one hand with a finger resting in the concave surface 15 with the ribs 16 and the adjacent fingers gripping the sides 17, in close proximity to the foetal scalp, the electrical connector 1 is rotated, by the other hand, with respect to the head member, in opposition to the torsion in the helical spring 3, whereby the arcuate needle 10 is withdrawn through the hole 12 into the cavity in the head member, which then has its flat surface 13 held against the foetal scalp by pressing with the finger resting in the concave surface 15, and the electrical connector 1 returned relative to the head member 2, whereby the arcuate needle 10 is forced back out through the hole 12 and through the foetal scalp, the looping of the point of the needle 10 back to the head member and through the hole 14, and the torsion applied by the helical spring 3, ensuring secure attachment of the electrode to the foetal scalp.

The arcuate needle 10 being normally urged, by torsion in the helical spring 3, through the hole 12 in the head member 2 and with the point of the needle looping back to the head member and through the hole 14, as shown in Figures 4 and 5, the radial arm 11 presses on the insulated additional electrode wire 19 closely adjacent to the exposed pin portion 22, which is thus forced to project from the hole 21 in the head member, to ensure insertion of the pin into a scalp with which the electrode is engaged by the arcuate needle.

To release the electrode from the foetal scalp, the head member 2 is held (as before) and the electrical connector 1 is rotated with respect to the head member in opposition to the torsion in the helical spring 3, whereby the arcuate needle 10 is withdrawn from the foetal scalp and into the cavity 9, and the head member is moved away from the the foetal scalp before being released for the arcuate needle to spring back to its position partly outside the head member.

Claims

1. A foetal scalp electrode of the type described provided with an additional electrically conductive electrode wire with a terminal at one end in the electrical connector, the additional electrode wire being insulated where it extends parallel to the wire with the radial arm and arcuate needle and into the cavity in the head member, the insulated additional electrode wire also passing between the radial arm and the normally adjacent side of the cavity to an additional hole between the cavity and the outside of the head member adjacent to the hole for the arcuate needle, and an electrically conductive pin is provided on the end of the additional electrode wire and projects from the additional hole in the head member.

2. A foetal scalp electrode as in Claim 1, wherein the additional electrode wire is a wire with an insulating coating except at its ends, one of which forms the electrically conductive pin, and the other of which makes contact with the respective terminal in the electrical connector.

3. A foetal scalp electrode as in Claim 1 or Claim 2, wherein the additional electrode wire is disposed between the insulating sheath and the helical spring along the length between the connecting member and the head member.

4. A foetal scalp electrode substantially as hereinbefore described with reference to the accompanying drawings.