Surgery: splint – brace – or bandage – Bandage structure – Skin laceration or wound cover
Reexamination Certificate
2000-03-02
2003-05-06
Lucchesi, Nicholas D. (Department: 3764)
Surgery: splint, brace, or bandage
Bandage structure
Skin laceration or wound cover
C604S361000, C602S041000
Reexamination Certificate
active
06559351
ABSTRACT:
TECHNICAL FIELD
The present invention relates to wound dressings and, in particular, to occlusion dressings. The wound dressing of the invention has a visible indicator so that a user can see when the dressing and determine whether it should be changed. The saturation colour change, depending on the amount of exudate, may in most cases indicate that a change of dressing is necessary.
BACKGROUND OF THE INVENTION
Wound dressings are widely used for many types of epithelial wounds and, in general, need to be changed at regular intervals to ensure that the wound and surrounding area remains as clean as possible. Occlusion dressings function by sealing the wound, thus preventing external contamination and keeping the tissue moist, which promotes healing. It is undesirable to change the dressing frequently since this negates the effect of the occlusion principle. However, when the dressing is saturated, it can no longer perform its function effectively. It would therefore be useful if the patient and carers responsible for changing wound dressings could be alerted when a change of dressing is required.
Dressings which indicate when they are saturated are known and one example is the dressing sold by Convetec under the trade mark SignaDRESS. In the SignaDRESS™ dressing, fluid leaks from the wound into an area behind an impermeable outer covering of the dressing causing a blister to become visible. Once the edge of the blister reaches an indicator line marked on the outer surface of the dressing, changing is required. The SignaDRESS™ dressing does, however, have certain disadvantages, the main one being that it is covered by a polymer film which restricts the flexibility of the dressing and prevents it from conforming to the contours of the wound site. In addition, the indicator is merely a blister on the surface of the dressing and may, in some cases, be difficult to read and, if allowed to enlarge, may become a pouch of fluid excessive to the requirements of a healing environment.
The present invention also provides a dressing which indicates when it needs to be changed. However, it functions in a completely different way from the SignaDRESS™ dressing.
SUMMARY OF THE INVENTION
In the present invention, therefore, there is provided a wound dressing comprising:
a. a covering release layer;
b. a dressing layer;
c. an indicator layer;
d. a transparent or translucent covering;
characterised in that the indicator layer comprises a non toxic indicator substance, which changes colour on contact with water, mixed with a diluting agent and the bonding layer comprises a water-impermeable mobile sticky polymer capable of bonding the indicator layer to the dressing layer and to the outer covering.
The advantage of the dressing of the invention is that when it becomes saturated and needs to be changed, liquid penetrates into the indicator layer, causing the indicator substance to change colour. The colour change is visible through the indicator bonding layer and the outer covering and so it is obvious to the person responsible that the dressing needs to be changed. In addition, unlike the SignaDRESS™ dressing, the indicator in the dressing of the present invention covers the entire area of saturation of the dressing. This makes it easy to tell if the dressing needs to be changed.
Covering release layers for dressings are known and are designed to be loosely attached to the dressing layer and impermeable to microorganisms. Examples of known types of covering release layers include paper with a siliconised surface or paper coated with a polymer. For this invention, polymer coated papers are preferred as they do not tend to leave residues on the dressing, which can be a problem with siliconised covering release layers. Paper coated with polyethylene has been found to be a particularly suitable covering release layer for use in this invention.
The dressing of the invention may be of any known type, for example an antiseptic-impregnated gel or other type of fibrous medium such as gauze. However, it is very much preferred that the dressing is of the hydrocolloid type. Hydrocolloid dressings are well known in the art and consist of a fine particulate powder which gels in the presence of body fluids and/or water. The hydrocolloid dressing may consist of a powdered gelling substance suspended in a colloidal suspending agent.
Gelling substances which have been used in hydrocolloid dressings include starch and, more recently, sodium carboxymethylcellulose, pectin and other moisture-absorbing particulate substances. Mixtures of any of these gelling agents may also be used.
The suspending agent should be water impermeable and mobile and it should be chosen such that it does not create an adverse reaction when placed in contact with a wound. Examples of suitable suspending agents include polyisobutylene, which may be mixed with one or more other polymers, such as polyethylene, and some carbohydrates. In some types of hydrocolloid dressings, the gelling substance and suspending agent have been replaced by a hydrogel.
A particularly suitable hydrocolloid dressing for the present invention is formed from sodium carboxymethylcefiulose, alone or with starch or other moisture absorbing particles suspended in polyisobutylene, which may be mixed with polyethylene or other polymers. The exact composition of the hydrocolloid will be chosen to provide the desired degree of moisture retention. One skilled in the art of hydrocolloid dressings would be aware of how this could be achieved.
The hydrocolloid dressing slowly absorbs moisture, which is retained in the area of the wound. There is, in many cases, a relationship of proportionality between the thickness of the dressing and the time taken for it to become saturated. In addition, the permeability of the dressing may be affected if the dressing is sterilized by irradiation.
One of the features of hydrocolloid dressings, which makes them particularly suitable for use in the present invention, is that the proportions of gelling substance and suspending agent can be chosen so that the dressing is impermeable to moisture until it become saturated. This means that no moisture reaches the indicator substance until the dressing is saturated and needs to be changed.
In dressings consisting of hydroxymethylceUulose (and optionally starch) suspended in polyisobutylene or a mixture of polyisobutylene and polyethylene, a suitable ratio of gelling substance to suspending agent is about 1:1.
The indicator substance may be placed in small dots on the outer surface of the dressing layer. Alternatively, the indicator layer may comprise a thin layer of a powdered indicator substance, which may be mixed with a diluent. The diluent is used in order to emphasise the colour change of the indicator substance. Thus, suitable diluents are of a light colour, often white, which will partially conceal the original colour of the dry indicator substance and make the colour change more noticable when the indicator substance is wet. Diluents which may be used in the dressing of the invention include sodium carboxymethyl cellulose and magnesium carbonate.
Suitable indicator substances include soluble dyes such as 0.25% crystal green, Mercurochromet™, cobalt salt moisture indicator and gentian violet or, alternatively, it would be possible to use any indicator with a colour change activated by enzymic catalytic action, provided that the appropriate enzyme is also provided in the indicator layer. An example of a system which uses an enzyme-activated colour change is the system used in analysing urine for the presence of glucose. This system employs glucose oxidase, peroxidase and a colourless hydrogen donor and, on contact with glucose, a coloured compound is produced. If glucose, as well as the enzymes, were imobilised in the indicator layer, contact with moisture would allow the components of the system to mix so that the colour change is produced. There are many other enzyme-activated colour change systems and any of these could be used in a similar manner to the glucose oxidase/peroxidase system.
T
Hamilton Lalita
Lucchesi Nicholas D.
T.G. Eakin Limited
Wallenstein & Wagner Ltd.
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