WO2008071941A2

WO2008071941A2 - Wound dressing

Info

Publication number: WO2008071941A2
Application number: PCT/GB2007/004742
Authority: WO
Inventors: Petr Zamouril; Nigel Richard Yates; Matthew Peter Duggan; Jan Hovorka
Original assignee: Electroband Ltd
Priority date: 2006-12-11
Filing date: 2007-12-11
Publication date: 2008-06-19
Also published as: EP2101862A2; GB2444703A; GB2444703B; WO2008071941A3; GB0624684D0

Abstract

A wound dressing comprising a conductive dressing for application to a wound site and a compression bandage for application over the conductive dressing is disclosed. The conductive dressing includes an insulator for electrically isolating the conductive dressing from the compression bandage when in use and an insulated lead for connection to a first terminal of a power source. The compression bandage includes an electrically conductive portion connectable to a second terminal of the power source.

Description

W

Wound Dressing

Field of the Invention

The present invention relates to an improved wound dressing.

Background to the invention

The body repairs connective tissue damage through the process of three distinct phases. Each phase has a specific sequence of events that differentiates its self from the others, although in reality these phases overlap during the healing process. The phases are:

• Inflammatory phase, where the body begins to clean away bacteria and initiate hemostasis;

• proliferative phase, where wound contraction occurs as a result of fibroblast proliferation, synthesis of collagen and granulation; and, • remodelling phase, where collagen production slows and is more organised to restore the properties of the skin at the wound site.

For healthy human beings these phases occur quite normally. However, in patients who suffer from conditions that effect blood flow to the wound the normal healing process is delayed or even halted. Diabetes, reduced circulation, infections, reduced mobility and some medications can all hinder the normal healing process.

The development of chronic wounds such as ulcers is primarily caused by poor circulation. In the leg, a reduction in blood flow can cause cell death and leads to open leg wounds (venous ulcers - an ulcer that occurs in the leg, typically above the ankle), which are unable to heal on their own.

A number of treatment options exist for venous ulcers which include protective wound dressings; extraction if wound exudates; antibiotics; electrotherapy; hyperbaric oxygen treatment; surgical treatment; and compression therapy. The type of treatment may depend on the severity of the wound and the mobility of the patient. Most treatment regimes will take months to fully heal a venous ulcer, therefore treatment that increase the tissue recovery rate are essential to the course of treatment employed.

The use of compression therapy to treat ulcers and accelerate the rate of healing has been highlighted many times around the world in the last decade. Compression is commonly used to treat oedema and other venous and lymphatic disorders of the lower limb.

Oedema is the accumulation of fluid in extra vascular tissue which leads to swelling. It results from the interaction between permeability of the capillary wall and hydrostatic and oncotic pressure gradient that exists between blood vessels and surrounding tissue.

The application of external compression initiates a variety of complex physiological and biochemical effects involving venous, arterial and lymphatic system. When the right level of compression is applied the effects of compression can be dramatic, reducing oedema and pain while promoting the healing effect of ulcers.

The degree of compression produced by a bandage system over a period of time will affect the rate of healing. The properties of the bandage can be quantified by four factors - the electrometric properties of the bandage, size and shape of the limb to which it is applied, skill of applying the bandage and the physical mobility of the patient.

The development of compression bandages has improved the treatment of leg ulcers by having the ability to apply a constant pressure treatment over a period of time and having the ability to accommodate patient activity and the patient's shape. Results from compression treatment of the lower leg to aid venous leg ulcers have shown that bandage pressures of 40mmHg at the ankle are typically required. However sub-bandage pressures are greatly influenced by several factors including posture, movement and bandage application technique.

Electrotherapy for wound healing relies on application of currents that replicate the electric fields that occur naturally within the body and stimulate cell growth during the wound healing process.

Natural body tissue possesses direct current electopotentials that regulate in part the healing process. Following tissue damage, a current (called a current of injury) is generated that is thought to trigger biological repair. Many studies have shown that localised exposure to low levels of electrical current that mimics this naturally occurring current of injury enhances the healing of soft tissue.

Importantly, evidence has been found to show that ulcers treated with electrotherapy demonstrated accelerated healing and the skin wounds have resurfaced faster with better tensile properties.

Studies on the type of electrical field have shown that pulsating electromagnetic fields dramatically accelerate the healing rates. There are a number of existing technologies for the application of electrotherapy treatment e.g, see the disclosure in US 5,433,735 to Zanakis et al. However, these techniques suffer from the disadvantage that they do not generate current flow through all portions of the wound. WO 02/098502 to Andino et al discloses a single bandage that encompasses a wound and the surrounding skin to overcome the limitations of previous technology.

Typical electrotherapy treatments are not continuous but applied daily for a typical period of 30 minutes. Therefore the patient requires the application of electrodes for each treatment session with standard electrotherapy treatments. This treatment approach is in conflict with the long-term benefits of compression therapy which shows the best results where compression is maintained for long periods of time with out interruption. Compression bandages are designed to be applied for up to 7 days typically without the need for medical intervention. The current application of compression treatment with electrotherapy treatment requires daily interference of the wound site to remove the compression bandage apply an electrotherapy electrode to the wound for the period of treatment. Following this with the removal of the electrode and redressing the wound with a compression bandage clearly reduces the effectiveness of the two treatments in combination.

Statement of invention According to an aspect of the present invention, there is provided a A wound dressing comprising a conductive dressing for application to a wound site and a compression bandage for application over the conductive dressing, the conductive dressing including an insulator for electrically isolating the conductive dressing from the compression bandage when in use and an insulated lead for connection to a first terminal of a power source, the compression bandage including an electrically conductive portion connectable to a second terminal of the power source.

The present invention seeks to provide an improved wound dressing that enables electrotherapy to be applied over the same time period as compression therapy without disruption of the compression dressing. Embodiments of the present invention are particularly suitable for the treatment of wounds like venous ulcers.

The wound care apparatus is comprised of two electrode components, the first component comprises an electrically conductive compression bandage that is wrapped around the limb being treated, over the top of the second electrode. The second component being the wound dressing electrode that is placed in contact with the wound. The wound dressing electrode is electrically isolated from the compression dressing electrode.

The application of the invention to wound treatment allows both compression therapy and electrotherapy treatments to be carried out on the patient over a period of time with out the need for any interference of the wound site for a period of up to 7 days. This provides an advantage over existing treatments, which require the daily removal of the compression bandage to treat the wound site with electrotherapy and then the replacement of the compression bandage until the next electrotherapy session is require. The existing treatment methods are an expensive and inconvenient method of treating venous ulcer wounds for both the healthcare provider and the patient.

Preferably, the conductive dressing has a size such that it is in contact with the entire wound.

Preferably, the compression bandage also covers the entire wound.

Preferably, the compression bandage is arranged to provide compression, of up to and including 40 mm Hg, to the wound area in order to promote wound healing via compression therapy.

Preferably, the conductive portion of the compression bandage comprises a woven material comprising electrically conductive elements of metal bonded fibres or metal wires. Preferably, the compression bandage is a tubular bandage or elastic bandage.

The conductive dressing preferably comprises an electrically conductive layer attached to an absorbent layer wherein the absorbent layer is coated with an electrically insulating layer. The conductive layer may be a woven material comprising electrically conductive elements of the types, metal bonded fibres or nanocrystalline impregnated fibres. Preferably, the absorbent layer is suitable for the absorption of extraneous matter found in the wound environment. The conductive layer may optionally be impregnated with an antimicrobial agent or may include a material having antimicrobial properties.

When in use, the compression bandage encircles the wound dressing. Preferably, the electrically insulating layer of the wound dressing, is interposed between the compression bandage and the electrically conductive layer of the wound dressing. Preferably, the electrically insulating layer is permeable to oxygen.

Preferably, the electrically insulating layer is impermeable to water and water vapour.

Preferably, the insulated leads are selected such that when under compression, the dimensions and profile of the connection lead does not cause discomfort to the wound site or under any part of site covered by the first electrode.

The compression bandage and wound dressing are arranged such that an electrical current can be applied to the wound site multiple times without the requirement to remove, wholly or in part, the compression bandage.

Brief Description of the Drawings

An example of the present invention will now be described in detail, with reference to the accompanying drawings, in which:

Figure 1 is a sectional view of a wound dressing according to an embodiment of the present invention;

Figure 2 is a sectional view illustrating selected aspects of the embodiment of

Figure 1 in more detail;

Figures 3a, b and c are respective sectional, exploded and plan views of selected aspects the embodiment of Figure 1 ; Figure 4 is a perspective view of the embodiment of Figure 1 in use; and,

Figures 5a and 5b are an exploded view and a sectional view of aspects of an alternate embodiment of the present invention.

Detailed Description Figure 1 is a sectional view of a wound dressing according to an embodiment of the present invention. The wound dressing includes a compression bandage 2 and a conductive dressing 3 that are applied to the site of an injured body part 1. The conductive dressing 3 is applied over a wound site 4 on the body part 1. The compression bandage 2 is applied over the conductive dressing 3. The conductive dressing 3 includes an insulating layer insulating the conductive portion of the conductive dressing 3 from the compression bandage 2 when in use. At least a portion of the compression bandage 2 is electrically conductive and allows an electrical current to be applied through the portion of the compression bandage 2 to the body part. The current then flows to the wound site of the injured body part 1to the conductive dressing 3.

An insulated flying lead 6 provides an electrical connection directly to the conductive dressing 3 to complete the electrical circuit. The insulation ensures the flying lead 6 is insulated from the compression bandage 2.

An optionally removable electrical lead 5 is connectable to conductive portion of the outer surface of the compression bandage 2.

Figure 2 is a sectional view illustrating selected aspects of the embodiment of Figure 1 in more detail. The electrically conductive dressing 3 is placed over the wound site first 4 so that it is preferably completely covered.

Figures 3a, b and c are sectional, exploded and plan views of the electrically conductive dressing 3 of Figure 1. The electrically conductive dressing 3 is preferably made up of several components. These include:

• an outer breathable electrically insulating layer 7; • an absorbent layer 8;

• an electrically conductive layer 9 suitable for contact with the wound site 4; and,

• an insulated lead 6 bonded to the electrically conductive layer 9 so that electrical connection can be made to the wound electrode.

It will be appreciated that not all of these components are essential and other configurations of electrically conductive dressings are possible. Figure 4 is a perspective view of the embodiment of Figure 1 in use. The electrically conductive dressing is applied to the wound site. The outer compression bandage 2 is then wound around the body part 1 at a predetermined tension to apply compression therapy to the body part 1. When electrical stimulation treatment is required, a temporary electrical connection is made with the bandage outer surface at any position via a connector 6. The connector can be a conductive clip or pad. The lead 6 of the dressing 3 is then connected to the other pole of the power source to complete the electrical circuit. After the electrical stimulation treatment the connector can be removed.

Figures 5a and 5b are, respectively, an exploded view and a sectional view of an alternate configuration of an electrically conductive dressing 3 suitable for use in an embodiment of the present invention. Whilst the illustrated configuration shares many similarities with that of of Figures 3a-c, in this configuration a wound dressing is used which has a second conductive patch 9 on opposing side of the insulating layer 7 to that of the first conductive patch 9. Each patch is connected to separate flying leads 6.

This arrangement removes the need for separate flying leads to be connected to the conductive compression bandage as it is conductive on both sides. In this manner, the second conductive patch 9 (the one that is not in contact with the wound site) is instead positioned in contact with the conductive portion of the compression bandage 2. The electrical circuit is then power source - flying lead - first conductive patch - wound site - conductive portion of compression bandage - second conductive patch - flying lead - power source.

Claims

1. A wound dressing comprising a conductive dressing for application to a wound site and a compression bandage for application over the conductive dressing, the conductive dressing including an insulator for electrically isolating the conductive dressing from the compression bandage when in use and an insulated lead for connection to a first terminal of a power source, the compression bandage including an electrically conductive portion connectable to a second terminal of the power source.

2. A wound dressing as claimed in claim 1 , wherein the conductive portion of the compression bandage comprises a woven material comprising electrically conductive elements of metal bonded fibres or metal wires.

3. A wound dressing as claimed in claim 1 or 2, wherein the compression bandage is a tubular bandage or elastic bandage.

4. A wound dressing as claimed in any preceding claim, wherein the compression bandage is cylindrical and the electrically conductive portion circumscribes the cylinder.

5. A wound dressing as claimed in any preceding claim, wherein substantially the entire compression bandage is electrically conductive.

6. A wound dressing as claimed in any preceding claim, wherein the conductive dressing comprises an electrical conductor attached to an absorbent layer wherein the absorbent layer is coated with an electrical insulator.

7. A wound dressing as claimed in claim 6, wherein the electrical insulator is a layer.

8. A wound dressing as claimed in claim 6 or 7, wherein the electrical conductor comprises a woven material comprising electrically conductive elements of metal bonded fibres or nanocrystalline impregnated fibres.

9. A wound dressing as claimed in claim 6, 7 or 8, wherein the conductor is impregnated with an antimicrobial agent or includes a material having antimicrobial properties.

10. A wound dressing as claimed in claim 6 or 7, wherein the insulator is substantially permeable to oxygen.

11. A wound dressing as claimed in claim 6, 7 or 10, wherein the insulator is substantially impermeable to water and water vapour.

12. A wound dressing as claimed in any preceding claim, wherein the conductive dressing further comprises: an outer breathable electrically insulating layer; an inner electrically conductive layer for contact with a wound site; an absorbent layer interposed between said inner and outer layers; and, an insulated lead bonded to the electrically conductive layer for electrical connection.

13. A wound dressing as claimed in any of claims 1 to 11 , wherein the conductive dressing further comprises. a breathable electrically insulating layer interposed between: a first electrically conductive layer for contact with a wound site; and, a second electrically conductive portion for contact with the conductive portion of the compression bandage; wherein an insulated lead is connected to each of the first and second electrically conductive layers for electrical connection to a power source, whereby the conductive portion of the compression bandage is connectable to the second terminal of the power source via the second electrically conductive layer and its respective lead.