WO2010040357A1

WO2010040357A1 - Electrical wound dressing having multiple cathodes

Info

Publication number: WO2010040357A1
Application number: PCT/DK2009/050265
Authority: WO
Inventors: Klaus Budig; Eric Wiebols; Christian Kaestner; Michael Svedberg; Jiri Kubicka; Ronny Slovak; Peter Uppman
Original assignee: Coloplast A/S
Priority date: 2008-10-06
Filing date: 2009-10-06
Publication date: 2010-04-15

Abstract

A wound care device comprising at a skin contacting surface at least two cathodes positioned to be placed on a wound surface and at least one peripheral anode positioned to be placed on healthy skin surface and comprising means for providing current between the at least two cathodes and the at least one peripheral anode.

Description

Electrical wound dressing having multiple cathodes

Field of the invention

The present invention relates to a wound care device comprising at the skin contacting surface at least two cathodes and at least one peripheral anode arranged at different positions surrounding the at least two cathodes.

Background

A wound, ulcer or sore may be defined as an injury to the skin and underlying tissue. Normally, a wound will heal by going through well-characterised healing phases, such as inflammation, granulation, epitheliazation and wound closure. All phases are regulated by a balanced action of proteases and signalling factors (cytokines and growth factors), which are essential to healing.

A chronic wound may be defined as a wound where the normal processes of healing have been diminished, reduced or disrupted in one or more of the above-mentioned phases. The reason for the disruption of one or more of the wound healing phases is not entirely understood as the wound healing process is widely described as a highly complex process. A few relevant factors have been pointed out in diminishing the healing process, such as alterations of growth factors, cytokines, proteases and intra- and extracellular elements in a specific wound, ulcer or sore.

A large number of methods and devices have been introduced in the past to speed up the wound healing process or alternatively to restart or revitalise a stagnant or stopped wound healing process. An example of such a method is to provide a moist wound healing dressing, which provides an optimal healing environment for the wound.

Another method for speeding up a slow or stopped wound healing process has been to apply electrical stimulation to the wound site. Electrical stimulation to the site of a wound is meant to imitate the natural electrical current in the cutaneous or subcutaneous layers and is believed to accelerate the wound healing process or restart a stagnant wound healing process, as mentioned in Gardner et. al., Effect of electrical stimulation on chronic wound healing: a meta-analysis, WOUND REP REG 1999;7:495-503. Gardner et. al. shows that electrical stimulation produces a substantial improvement in the healing of chronic wounds in an analysis of fifteen different studies on the subject.

US patent application No. 2006/173523 discloses a device for electrical stimulation of wounds, where a number of electrodes are placed on healthy tissue surrounding a wound site. In one example, the electrical stimulation of the wound is performed using two electrodes, where the electrodes are on the opposite sides of the wound. Each electrode is selectively connected to a positive and a negative terminal, which means that the current can flow selectively, to or from each electrode.

US patent No. 5,814,094 discloses a device for including tissue healing and regeneration, where a treatment electrode is placed in contact with the surface of a wound to be treated and a return electrode is placed in contact with intact skin proximal to the wound. The electrodes are connected to a power source by cables. The treatment electrode is silver impregnated or provided with silver-coated nylon, where the treatment electrode distributes silver ions into the wound site.

European patent application No. 1 395 332 discloses an electrode system that includes two electrodes that are adapted for connection to a power source. The electrodes are shaped and oriented in a circular first electrode located at and covering the wound site and a second electrode is shaped as a ring fully encircling the first electrode. The second electrode may be located outside or partially within the wound site. The electrode system further comprises an insulative element between the anode and the cathode.

The electrophysiology of the body has sometimes been described as a complex network of circuitry, where the skin and the subcutaneous layers may be measured as having an electrical impedance, as disclosed in US patent No. 6.633,777, or simply as having an electrical resistance. Electrical resistance is a measure of the degree to which an object opposes an electric current through it, while the electrical impedance extends the concept of electrical resistance in alternating current circuits.

Summary

In one aspect of the present invention there is provided a wound care device comprising at a skin contacting surface at least two cathodes positioned to be placed on a wound surface and at least one peripheral anode positioned to be placed on healthy skin surface and comprising means for providing current between the at least two cathodes and the at least one peripheral anode.

When using a wound care device for electrical stimulation of a wound that has a single cathode in a central area of the wound care device, there is a significant risk that the cathode will ionise during a period of electrical stimulation of a wound and the electrical communication between the wound area and the cathode will decrease. The present invention solves this problem by having at least two cathodes, which are to be placed on the wound surface and by increasing the number of cathodes, the impact, affect or ionisation of each cathode may be reduced significantly.

Within the scope of the present invention, the meaning of the term "cathode" is an electrode capable of electrical communication with a medium, such as the wound surface or the skin surface and the electrode is capable of transmitting and/or receiving electrical current via the cutaneous layer, the subcutaneous layer or via any suitable tissue in the body. The meaning of the term "anode" is an electrode that provides the opposite pole from the cathode, i.e. the anode transmits current and the cathode receives it and vice versa.

The anode of the wound care device is preferably arranged outside a wound area, in a way that the anode comes in electrical communication with a healthy skin surface, while the cathode is positioned inside the external boundaries of the wound. By placing the anode outside the wound, it is possible to electrically stimulate the wound area from the outside and in a direction towards the at least two cathodes, which are usually positioned inside the wound area. In some stages of the natural wound healing process, it may be advantageous that the current may be reversed, in a way that the current travels from one of the at least two cathodes and towards the peripheral anode, such that the electrical stimulation may be performed from the inside of the wound surface and towards the periphery of the wound surface.

In one embodiment of the present invention the wound care device may comprise two or more peripheral anodes positioned in a radial direction away from the at least two cathodes. By providing at least two or more peripheral anodes, it is possible to distribute the anodes around the wound area and the electrical stimulation may be performed from different positions around the wound. This means that the electrical stimulation provided by the wound care device stimulates the wound into healing more evenly from the outside perimeter of the wound towards the inside and not only on one side. In other embodiments of the present invention the number of anodes might be increased to three, four, five, etc, in a way that the wound care device is arranged to electrically stimulate the wound from multiple sides of the wound. This should increase the healing rate of the wound and increase the likelihood that the wound heals evenly from the outside and towards the centre of the wound.

In one embodiment of the present invention, the at least two cathodes positioned to be placed on a wound surface and at least one peripheral anode positioned to be placed on healthy skin surface and comprising means for providing current between the at least two cathodes and the at least one peripheral anode.. Typically, a wound care device has a central area, which is aligned over the central area of the wound, in a way that the wound care device covers the entire surface of the wound. In a situation where a patient or a user has a wound that may be seen as irregular, it may be difficult to position the wound care device onto the wound, such that the central area of the wound care device is positioned onto the central area of the wound. Therefore, it may be advantageous that the cathodes are positioned slightly away from the central area of the wound care device, in a way that there is an increased likelihood that at least one of the at least two cathodes may be positioned into the central area of the wound.

Within the scope of the present invention it is to be understood that the cathodes may be placed away from each other. In some embodiments of the present invention it may be advantageous to position the cathodes adjacent to each other. In one embodiment of the present invention, the wound care device may comprise three or more cathodes. This means that if one of the cathodes becomes ionised, the wound care device has at least two redundant cathodes which may still be capable of transmitting or receiving the electrical current to or from the at least one peripheral anode and the wound care device may continue stimulating the wound. The ionisation of the cathode may also be problematic in that the ionisation causes an increase in the acid concentration in the tissue surrounding the cathode. The acid concentration may contribute to a slower healing rate of the wound and may even lead to tissue decomposition or decay, which may cause problems during the wound healing process. Thus, by arranging the wound care device with additional cathodes, the wound care device may have redundant cathodes, such that the risk of having a non-functional wound care device due to ionised, disconnected or otherwise non-functional cathodes is reduced considerably. Furthermore, the risk of increased acid concentration in the wound, due to ionisation of the cathodes, may be reduced. In one embodiment of the present invention, the at least two cathodes may be arranged equiangularly relative to each other. The angles may be understood as the cathodes would be placed on the periphery of a unit circle and the angles may be measured between an axis that originates in the centre of the circle and a central area of the cathode for each of the cathodes. This means that when a wound care device has two centrally placed cathodes, which may be arranged equadistally from the centre of the wound care device, the angle between the two cathodes is approximately 180°, 360° / 2. In an embodiment where the wound care device has N cathodes, the angle between the cathodes is 360° / N, or when N = 4, the angle between the cathodes is substantially 90°. The precision of the abovementioned angles is ±5 degrees. Within the scope of the present invention, the meaning of the word "equiangular" is when all angles are equal.

The use of at least two cathodes to stimulate a wound may lead to a situation where one cathode interferes or disturbs the other cathode, i.e. when the two cathodes are active at the same time. Thus, in one embodiment of the present invention, the at least two cathodes may each be selectively switched to one or more current sources. This means that the means for providing current between the anode and the at least two cathodes is able to selectively switch the individual cathodes on or off, in a way that the cathodes are in electrical communication with one or more current sources. Thus, it is possible to have one cathode active and the at least one other cathode inactive when electrical current is transmitted from the anode to the cathode via the bodily tissue. This ensures that the transmission of current goes from one anode to one cathode or vice versa and that the current does not leak into any other cathodes.

In one embodiment of the present invention, the at least two cathodes and/or the at least one peripheral anode may be made of biocompatible materials selected from the group of thin metal, metallic paint, printed metallic pigments, metal foil or conductive hydrogel. Examples of a thin metal, metallic paint or metallic foil may be Ag, AgCL, Au, Al, Cu and other highly conductive biocompatible metals.

In one embodiment of the present invention, the wound care device may have N anodes and N cathodes and the electrical current is provided between anode n and cathode n. This means that each anode has a corresponding cathode and vice versa and the electrical stimulation is provided selectively in pairs. This means that if there are 5 cathodes, N=5, there are 5 anodes as well and when anode number 1 , n=1 , is used to transmit or receive current, the opposite cathode is cathode 1. This means that the current path into the wound may be selected beforehand and the current path is constant for each pair.

In one embodiment, the anode and cathode pairs may be selectively activated, in a way that only one pair is active at any time. One alternative is to activate more than one pair at a time and switch at regular intervals to other pairs, such that all electrode pairs are used in one cycle of electrical stimulation. Another alternative is to activate all cathode pairs at the same time, where each cathode pair have their own current source and therefore the current transmission from one pair does not interfere with a current transmission from another pair.

In one embodiment of the present invention, the electrical current may be provided by connecting one peripheral anode to a single current source and switching between the at least two cathodes. The advantage of switching between the cathodes is that the cathodes are less likely to ionise and it would furthermore increase the distribution of the electrical current in the wound.

Brief Description of the Drawings

The invention will be discussed further with reference to the following example embodiments wherein,

Fig. 1 is a top view of one embodiment of a wound care device according to the present invention,

Fig. 2a and 2b is a top view of the same, showing the current pathways from the anode to the respective cathodes,

Fig. 3 is a top view of another embodiment of a wound care device having four anodes and four cathodes,

Fig. 4 is a schematical electrical diagram of one embodiment of the present invention and

Fig. 5 is a perspective view from below of one embodiment of the present invention. Detailed Disclosure

Fig. 1 is a top view of a wound care device 1 according to the present invention, wherein the wound care device comprises a backing layer 2, which is placed on top of a wound surface 3. The wound care device comprises two cathodes 4a, 4b, which are positioned in a central area of the wound care device 1. The wound care device is further provided with one anode 5, which is positioned in the peripheral area of the backing layer 2 of the wound care device 1. The means to provide the electrical current in the wound care device are omitted from the drawings, however the placement and the wiring of the circuitry should be obvious to the skilled person based on the present invention.

The wound care device 1 is positioned on top of the wound 3, such that the centrally placed cathodes 4a,4b are positioned in a central area of the wound 3 within the outer edge 6 of the wound 3 and where the anode 5 is positioned on healthy skin surface outside the outer edge 6 of the wound 3. During the electrical stimulation of the wound, where the current flows from the anode 5 towards the cathodes 4a, 4b it is possible to reduce the ionisation of the cathodes 4a, 4b by having two cathodes instead of one and the reduction in ionisation is approximately 50% on each cathode if the current flows evenly to both cathodes 4a, 4b.

Another possibility of performing the electrical stimulation using the wound care device of Fig. 1 could be to have only one cathode 4a, 4b active at a time as may be seen in Fig. 2a and 2b. For example when the electrical current 7 is transmitted from anode 5 to cathode 4a, cathode 4b is disconnected from the current source using a switch and when the current 7 is transmitted to cathode 4b, cathode 4a is disconnected from the current source. This method of switching between electrodes could also be performed using a more alternative number of cathodes, for example 3, 4, 5, 6 or 7 cathodes. The physical size of the cathodes and the wound care device would be the only limiting factor when choosing the number of cathodes, as it would not be advantageous to have the cathodes in electrical communication with each other when the current source is switched from one cathode to the other. In other situations, where different methods for electrical stimulation of the wound are chosen, it might be advantageous to activate cathodes in pairs, three or more or all at a time.

Fig. 3 shows another embodiment of the present invention, where the wound care device 1 1 is provided with four cathodes 14a-14d and four anodes 15a-15d and the electrical stimulation of the wound is performed by transmitting current between four different anode/cathode pairs, anode 15a to cathode 14a, anode 15b to cathode 14b, anode 15c to cathode 14c and anode 15d to cathode 14d. The electrical stimulation could be performed simultaneously for all anode/cathode pairs, one anode/cathode pair after the other anode\cathode pair, via non-sequential or random selection of anode/cathode pairs.

Fig. 4 shows a schematic wiring diagram of a wound care device having N cathodes K1- Kn and N central anodes A1 - An. The electrical circuit in this embodiment has one battery BT1 and one current source CS1. Each anode AI-An has its own electrical switch SW1A - SWnA and each cathode has its individual switch SW1 B-SWnB in order to connect the cathodes and anodes respectively to the electrical circuitry of the wound care device. The resistance in the skin and subcutaneous surface between the anode and cathode is referred to as RI-Rn. This embodiment allows each anode and cathode to be individually controlled, such that a control means can control which are connected and disconnected at any time. In this configuration it is not necessary to activate the anodes and cathodes in pairs, but it would be possible to activate any number of anodes and any number of cathodes at any time. The preferred method of activating the anodes and cathodes may be different from one user to the other and from one type of wound to another.

Fig. 5 shows another embodiment of a wound care device 21 according to the present invention in a side perspective view from below. The backing member 22 has seven anodes 25a-25f on the skin contacting surface 28. The backing member is arranged with a number of through-going cut outs 30, which define flaps 29, which are capable of following the inner contour of a wound, in a way that the loose ends of the flaps 29 are substantially in the bottom of the wound. Seven cathodes 24a-24f are positioned on the skin contacting surface 28 of the flaps 29, such that when the flaps 29 follow the contour of the wound, the cathodes 24a-24f come in contact with a central area of the wound. The electrical current of the electrical wound stimulation travels from one or more of the anodes 25a-25f towards the cathode 24a-24f, which ensures that the wound is stimulated from the outside and towards the centre of the wound. The method of electrical stimulation may be any of the methods disclosed in the present invention with regards to the other embodiments of the present invention.

Claims

1. A wound care device comprising at a skin contacting surface at least two cathodes positioned to be placed on a wound surface and at least one peripheral anode positioned to be placed on healthy skin surface and comprising means for providing current between the at least two cathodes and the at least one peripheral anode.

2. A wound care device according to claim 1 , wherein the wound care device comprises two or more peripheral anodes positioned in a radial direction away from the at least two cathodes.

3. A wound care device according to any of the preceding claims, wherein the at least two cathodes are positioned at a distance from a central area of the wound care device in a radial direction towards the outer periphery of the wound care device within an area of the skin contacting surface that is to be positioned on the wound surface that is the centre of the wound care device and the at least one peripheral anode.

4.A wound care device according to any of the preceding claims, wherein the wound care device comprises three or more cathodes.

5.A wound care device according to any of the preceding claims, wherein the at least two cathodes are arranged equiangularly relative to each other.

6.A wound care device according to any of the preceding claims, wherein the at least two cathodes are each selectively switched to one or more current sources.

7.A wound care device according any of the preceding claims, wherein the at least two cathodes and/or the at least one peripheral anode are made of biocompatible materials selected from the group of thin metal, metallic paint, printed metallic pigments, metal foil or conductive hydrogel.

8. A wound care device according to any of the preceding claims, wherein the wound care device has N anodes and N cathodes and the electrical current is provided between anode n and cathode n.

9.A wound care device according to any of the preceding claims, wherein the electrical current is provided by connecting one peripheral anode to a single current source and switching between the at least two cathodes.