Sealed medical electrode package

0001This invention relates to a sealed medical electrode package.

0002Medical electrodes used, for example, in external cardiac defibrillators typically have a flexible non-conductive backing sheet bearing a conductive gel layer. Since the gel layer rapidly deteriorates if left open to the atmosphere, such electrodes are normally sealed, usually in pairs, in a gas-impermeable package which is opened just before the electrodes are deployed for use. There are several known techniques for packaging such electrodes, but all require some form of outer protective packaging which needs to be removed before the electrodes themselves are handled by the operator.

0003An electrode package according to the preamble of claims 1 and 6 is known from <patcit id="pcit0001" dnum="US2003017743A"><text>US-A-2003/017 743</text></patcit>.

0004It is an object of the invention to provide an improved sealed medical electrode package which can be manufactured more cheaply and simply than existing packages while still protecting the conductive layers against the external environment.

0005Accordingly, a first aspect of the invention provides a sealed medical electrode package according to claim 1.

0006The first aspect of the invention provides a technique whereby there is no extra external outer packaging needed to protect the environmentally sensitive elements of the electrodes, thereby retaining shelf life, using a method which also allows easy rapid deployment while significantly reducing production cost.

0007According to a second, independent aspect of the invention there is provided a sealed medical electrode package according to claim 6.

0008Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: <ul id="ul0001" list-style="none"><li><figref idref="f0001">Figure 1</figref> is a schematic cross section through a typical medical electrode according to the prior art.</li><li><figref idref="f0001">Figures 2 to 4</figref> are schematic cross-sections showing successive stages in the manufacture of an electrode package according to an embodiment of the first aspect of the invention.</li><li><figref idref="f0002">Figure 5</figref> is a plan view of the final electrode package of <figref idref="f0001">Figure 4</figref>.</li><li><figref idref="f0003">Figure 6</figref> is a schematic cross-section through an electrode package according to an embodiment of the second aspect of the invention.</li><li><figref idref="f0004">Figure 7</figref> is a plan view of the final electrode package of <figref idref="f0003">Figure 6</figref>.</li></ul>

0009It will be understood that the drawings are not to scale and that, in particular, the thicknesses of the various layers shown in <figref idref="f0001">Figures 1 to 4</figref> and <figref idref="f0003">6</figref> has been greatly exaggerated.

0010<figref idref="f0001">Figure 1</figref> is a cross section through a conventional hydrogel electrode used, for example, for external cardiac defibrillation or medical monitoring. It comprises a flexible non-conductive backing sheet 10 made, for example, of a thin flexible polymer, and having opposite major surfaces 10A and 10B. A conductive layer 12 is deposited on the surface 10B and a final conductive gel layer 14 is deposited on the layer 12, the gel layer 14 being designed for interface with a patient's skin. The conductive layer 12 is preferably a homogeneous, solid, thinly deposited metal layer or a conductive ink. The gel layer 14 is preferably a hydrogel layer. Suitable materials for the layers 12 and 14 are well known in the art. A conductive stud 16 extends through the backing sheet 10 to the interface between the layers 12 and 14. The stud 16 is designed to accept a snap-on connector 18 at one end of a lead wire 20. Alternatively, the lead wire 20 could be fixed to the stud 16. These arrangements allow electrical connection to the gel layer 14 while the electrode is in position and deployed on a patient. The construction of this type of stud connection is well know to those skilled in the art.

0011As mentioned, electrodes of the type shown in <figref idref="f0001">Figure 1</figref> are usually packaged in pairs in a separate outer package. The embodiment of the first aspect of the invention, <figref idref="f0001 f0002">Figures 2 to 5</figref>, avoids the need for a separate outer package. In <figref idref="f0001 f0002">Figures 2 to 5</figref> the same reference numerals have been used for the same or equivalent components of <figref idref="f0001">Figure 1</figref>.

0012<figref idref="f0001">Figure 2</figref> shows two electrodes of the type described with reference to <figref idref="f0001">Figure 1</figref> laid end-to-end with a common release liner 22 applied to the exposed surfaces of the gel layers 14. The release liner 22 protects the adhesive nature of the gel layers and typically comprises a silicon-coated paper base.

0013Now, as indicated by the arrow in <figref idref="f0001">Figure 2</figref>, the two electrodes are folded over one upon and in register with the other so that their respective conductive gel layers 14 are disposed face-to-face, <figref idref="f0001">Figure 3</figref>, with the release liner 22 intervening between the two facing surfaces of gel layers. As seen in <figref idref="f0001">Figure 2</figref>, a continuous line of adhesive 24 extends around the peripheral edge of the backing sheet 10 of the right hand electrode (as seen in <figref idref="f0001">Figure 2</figref>). After the electrodes have been folded over as seen in <figref idref="f0001">Figure 3</figref> the peripheral edges of the two backing sheets are pressed together to hermetically seal the edges, <figref idref="f0001">Figures 4</figref> and <figref idref="f0002">5</figref>. This forms a gas-impermeable pocket containing the gel electrodes 14.

0014A pair of tabs 26 are provided, each attached to, or integral with, a respective backing sheet 10. These tabs allow the two electrode backing sheets be peeled apart along the line of adhesive, thereby separating the electrodes for deployment and use. Once opened, the release liner 22 can be peeled away and the electrodes placed upon the patient. In the preferred embodiment the adhesive is a biocompatible heat sensitive glue (i.e. liquid when heated) which retains the backing sheets 10 hermetically sealed under normal handling yet allows them to be peeled apart without damage to either. Glue with these characteristics is well known to those skilled in the art. If desired the tabs 26 may be integral extensions of the backing sheets 10, rather than separately attached. In such case, the adhesive would not extend on to the tabs.

0015The foregoing has assumed that the backing sheets 10 are separable along the line of the adhesive 24. However, if a permanent adhesive is used the backing sheets 10 can be separated by providing a line of weakening 28, <figref idref="f0002">Figure 5</figref>, along the inside of the adhesive, so that the sheets 10 tear along this line as they are separated. Of course, any such line of weakening must not significantly allow the ambient atmosphere to enter the interior of the package before the package is opened.

0016In an alternative embodiment the peripheral edges of the two backing sheets 10 are sealed by a clamping ring. The ring is in two circumferential halves that snap together to form a single ring running around and sealing the peripheral edges of the backing sheets 10. This ring gives the electrodes a general rigidity. In this case the backing layers 10 have a line of weakening 28 on the inside of the clamping ring. The electrodes can then be readily torn out of the ring to separate them and open the protective pocket.

0017<figref idref="f0003">Figures 6</figref> and <figref idref="f0004">7</figref> show an electrode package according to an embodiment of the second aspect of the invention. In <figref idref="f0003">Figures 6</figref> and <figref idref="f0004">7</figref> components the same as or equivalent to those of <figref idref="f0001 f0002">Figures 1 to 5</figref> and have been given the same reference numerals. To avoid unnecessary repetition, only the differences from the embodiment of <figref idref="f0001 f0002">Figures 1 to 5</figref> will be described.

0018In the package of <figref idref="f0003">Figures 6</figref> and <figref idref="f0004">7</figref> the peripheral edges of the backing sheets 10 are not sealed together as shown in <figref idref="f0001">Figure 4</figref> of the previous structure. Instead, the two electrodes, each comprising the layers 10, 12 and 14, are enclosed in an envelope or pocket 30 comprising two flexible sheets 32 of gas-impermeable material of a kind well-known in the art. The sheets 32 are heat-sealed at their periphery 34 and a pair of tabs 36 are each integral with, or fixed to, a respective sheet 32 to allow them to be peeled apart.

0019To allow the conductive studs 16 and associated lead wires 20 to be accessible without opening the package, each sheet 32 has a respective aperture 38 surrounding each stud 16 at a distance and exposing each stud 16 for connection to the lead 20. To maintain the gas-tight integrity of the package, the periphery of each aperture 38 is sealed, e.g. by a peel-to-release adhesive 40, to the respective backing sheet 10.

0020The invention is not limited to the embodiments described herein which may be modified or varied without departing from the scope of the claims.