GB2473321A - A spaced fabric for use as a compression bandage - Google Patents

Abstract

A single-layer compression bandage comprising a three-dimensional fabric composed of two separate fabric layers interconnected by a monofilament yarn which maintains a space between the first and second fabric layers. The fabric layers are knitted and may comprise of one or more yarns selected from polyester, polyamide, polypropylene, spandex, cotton, viscose, lyocell, wool or silk, or combinations thereof. The interconnecting yarn is a monofilament yarn selected from polyester, polybutylene terephthalate (PBT), polypropylene and/or polyamide (nylon). The layers and interconnecting yarn may have specific dtex values.

Description

Pressure Actuator The present invention relates to a pressure actuator for use in applications such as compression therapy for venous leg treatment, and which is, for example, able to provide a more advantageous pressure profile on a venous leg, accelerating the healing process.

Venous leg ulcer is one of the more common illnesses in developed countries. About 1-2% of the adult population in the UK suffers from active ulceration during their lifetime, and there is evidence that similar percentages are reported internationally. This creates considerable demands upon all healthcare authorities in terms of treatment costs and nursing resources. In the EU, the cost of treating patients with venous leg ulcer accounts for 1-2% of the overall healthcare expenditure. In the US, about 2 million working days are lost each year because of leg ulcer problems and the treatment cost is enormous. It is estimated that the direct cost of management and treatment of venous leg ulcers to the National Health Service SI.* (NHS) in the UK is about �650 million per annum, which is 1-2% of the total UK healthcare S....

* expenditure. * S

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*::: Jmproving the quality of life for an ever increasing ageing population is a key issue in healthcare and medical research. It has been recognised that venous leg ulceration is a S... p. *.

: .: common problem throughout the Western world. Venous leg ulcers are the most frequently occurring type of chronic wound, accounting for over 70% of the lower extremity ulceration and the recurrence rates can be as high as 72% within one year. Leg ulcers are exacerbated by a lack of physical activity and irregularities in blood circulation. Mostly, it is elderly people who are prone to develop Deep Vein Thrombosis (DVT), varicose veins and venous leg ulcers, but over 40% of patients suffer prior to age 50, and 13% before the age of 30.

It goes without saying that it is important that a person's arterial and venous systems work properly without causing problems to blood circulation around the body. Pure blood flows from the heart to the legs through the arteries taking oxygen and food to the muscles, skin and other tissues. Blood then flows back to the heart carrying away waste products through veins. The valves in the veins are unidirectional which means that they allow the venous blood to flow in an upward direction only. If the valves do not work properly, or there is insufficient pressure in the veins to push the venous blood back towards the heart, pooling of blood in the veins takes place and this results in a greater pressure on the skin. Because of the higher pressure and lack of availability of oxygen and food, the skin deteriorates and eventually an ulcer forms. The initial indications of venous leg ulcers are swollen veins (varicose veins) and blood clots in veins (DVT).

There is no medication or surgery to cure venous leg ulcerations. It has been widely accepted that the only efficient treatment for venous leg ulcers is compression therapy, to treat the underlying venous insufficiency. Compression bandaging is considered as the "gold standard" for managing venous leg ulcers and treating the venous insufficiency. For patients *..

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* with venous disease, the application of sustained graduated external compression or pressure ** *5* * * from the ankle to the area under the knee can help blood circulation by forcing fluid from the * * . * S. interstitial spaces back into the vascular and lymphatic compartments. This enhances the flow of blood back to the heart, improves the functioning of valves and calf muscle pumps, **** * reduces a edema and prevents the swelling of veins.

S SeeS S * * Consequently, the market for healthcare and medical textile devices is considerable.

In the EU alone, sales of medical textiles are worth US$7 billion, and already account for 10% of the market of technical textiles. The EU sector consumes 100,000 tonnes of fibre per annum and is growing in volume by 3-4% a year. The global medical device market was valued at over US$100 billion, of which US$43 billion was generated from the US market.

Western Europe is the second largest market and accounts for nearly 25% of the global medical device industry. The UK has one of the largest medical device markets in the world.

The market is dominated by the NHS which accounts for approximately 80% of healthcare expenditure, even though there are fewer private sectors. It is forecasted that the share of hygiene and medical textiles would be 12% of the global technical textiles market and would account for about US$4.1 billion.

The healthcare and medical devices market is being driven by: * population growth in developing countries; * the ageing of the population in developed countries; * rising standards of living and higher expectations of quality of life, * changing attitudes to health; and * the emergence of innovations and the availability of increasingly high level technology.

. It is a usual practice to ensure an external compression is applied in a graduated : fashion, with the highest pressure being applied at the anide and a lower pressure being applied higher up the leg. It has been proven that a graduated pressure applied to the leg of a person suffering from a venous leg will improve blood circulation and enhance the healing process. The optimal value for the degree of pressure required will vary according to a S number of factors, including the severity of the condition and the height and limb size of the patient.

The major objective of compression therapy is to achieve an external sub-bandage sustained pressure of about 40 mml-lg at the ankle, reducing to approximately half the pressure at the knee, with a gradual compression and uniform pressure distribution. Generally this is taken as a guide, because there is some debate regarding these figures as there are numerous influential factors. These factors include: * The size and shape of the patients' limb. The pressure applied by a bandage depends on the circumference of the limb. Generally the lower limb has a smaller circumference at the ankle than at the calf or knee. Therefore, in accordance with the principle of Laplace's law, the pressure would be lower at the calf and knee than at the ankle, so as a consequence a graduated pressure is achieved. A variance in size and shape will change the pressure considerably. For example, for a patient with a relatively small, thin lower limb, the pressure would be significantly higher than for a patient with a large, broader lower limb.

* The mobility of the patient as the compression therapy works in conjunction with the ability of the calf muscle to contract and relax creating the necessary pump action.

* The elasticity (stretch & recovery) and other tensile properties of the bandage, as these influence the degree of extensibility and therefore the tension at which the * * bandage is applied to the limb. **.

: *.: * The number of layers and width of bandage also influence the external sub-bandage pressure. * S S. S *5S

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* **. According to Laplace's law, the sub-bandage pressure is directly proportional to the **.

: * * bandage tension and is inversely proportional to the circumference of the limb: Pressure (mmHg) = Tension (Kgf) x n x K Circumference (cm) x Bandage width (cm) Where: n = the number of bandage layers applied K is a constant 4620 There are specific recommendations to be followed, and these are that all patients are to be adequately assessed and measured prior to the application of compression therapy which follows the standard recommendations from the Royal College of Nursing. There is a high risk of severe skin reactions through to possible leg necrosis with the inappropriate application of the current compression bandage systems. The assessment should also include the status of the patient. Compression therapy has to be considered in conjunction of mobility, rest, exercise, leg elevation as well as the patients' health, diet and mental health.

The compression bandage exerts external pressure onto a limb, which assists the interstitial pressure and improves venous return and reduces superficial venous hypertension.

Facilitating effective venous return of blood and the vital blood circulation is crucial for the healing of ulceration. The ability to generate and maintain this sub-bandage pressure is determined by the bandage structure, the elastomeric properties of yarns and the finishing treatments applied to the fabric.

* The sustained graduated compression mainly depends upon the uniform pressure ***** * * distribution of different layers of bandages in which textile fibres and bandage structures play *S. * S

a major role. *5S *

Compression bandages are mainly classified as elastic and non-elastic. Elastic S...

* * compression bandages are categorised according to the level of pressure generated on the angle of an average leg. Class 3a bandages provide a light compression of 14-17 mmHg, moderate compression (18-24 mmHg) is imparted by class 3b bandages and 3c type bandages impart high compression between 25 and 35 mmHg. The 3d type extra high compression bandages (up to 60 mmHg) are not often used because the very high pressure generated will reduce the blood supply to the skin. Typically, approximately 30-40 mml-Ig at the ankle, reducing to about 15-20 mmHg at the calf, is generally adequate for healing most types of venous leg ulcers.

Different types of compression bandages are used in different countries. In the UK, a four-layer compression system is widely used; in e.g other EU countries and Australia a non-elastic two-layer short stretch bandage regime is the standard treatment. However, the past few years have given rise to increasing concerns relating to the performance of bandages, especially pressure distribution properties for the treatment of venous leg ulcers. This is because compression therapy is a complex system and has required two or multi-layer bandages, and the performance properties of each layer are different to the other layers. This has a negative effect on the quality of life and comfort of the patients.

A typical four-layer compression bandage system comprises a padding bandage, a crepe bandage, a high compression bandage and a cohesive bandage. Both the two-layer and four-layer systems at least require the padding bandage (wadding or orthopaedic wool) that is applied next to the skin and underneath the short stretch or long stretch compression bandage.

A plaster-type non-elastic bandage, Unna's boot, is favoured in the USA. However, * compression is achieved by a three-layer dressing that consists of Unna' s boot, continuous *.*SS * * gauze dressing, followed by an outer layer of elastic wrap. It should be stressed that Unna's *.s. * *

boot, being rigid, is uncomfortable to wear and medical professionals are unable to monitor the ulcers after the boot is applied. * S.. S..

: * A variety of padding bandages are used beneath the compression bandage as a padding layer in order to evenly distribute the pressure and give protection to bony prominences. They absorb high pressures created at the tibia and fibula regions. It is of note that the structure of a padding bandage is regarded as an important factor in producing a uniform pressure distribution.

The padding bandages commercially available are nonwovens that are mainly used to distribute the pressure exerted by the short stretch or compression bandages evenly around the leg; otherwise higher pressure at one point not only damages the venous system but also promotes arterial disease. In contrast, application of an inadequate pressure cannot help to heal the venous ulcers. Even if the compression bandage is applied at the correct tension it is probable that excessive pressure will be generated over the bony prominences of the leg as the leg is not circular in shape.

As there is a need to distribute the pressure equally and uniformly at all points of the lower limb, the padding bandages should have the capability to absorb high pressure created at the tibia and fibula regions. Wadding can also help to protect the vulnerable areas of the leg from generating extremely high pressure levels as compared to those required along the rest of the leg. However, research carried out by the inventors involving the ten most conmionly used commercial padding bandages produced by major medical companies has shown that there are significant variations in the properties of commercial padding bandages.

More importantly, the commercial bandages did not provide the desired uniform pressure distribution as they did not distribute the pressure evenly at the ankle as well as the calf : region. The integrity of the nonwoven bandages is also of great concern. When pressure is applied using compression bandages, the structure of the nonwoven bandages may collapse *. and the bandage would not impart a cushioning effect to the limb. The comfort and * *** cushioning effects are considered to be essential properties for padding bandages because *..* * . . they stay on the limb for several days.

A wide range of compression bandages is available in the Drug Tariff but each of them has different structure and properties, arid this influences the variation in the performance properties of bandages. In addition, long stretch compression bandages tend to expand when the calf muscle pump is exercised, and the beneficial effect of the calf muscle pump is dissipated. It is a well established practice that elastic compression bandages that have an extension of up to 200% are applied at 50% extension and at 50% overlap to achieve the desired pressure on the limb. It has always been a problem for nurses to exactly stretch the bandages at 50% and apply without losing the stretch from ankle to calf, although there are indicators for the desired stretch (rectangles becoming squares) in the bandages. The elastic compression bandages are classified into four groups (3a, 3b, 3c and 3d) according to their ability to produce predetermined levels of compression and it has always been a problem to select a right compression bandage for the treatment. The inelastic short stretch bandage (Type 2) system has the advantage of applying at full stretch (up to 90% extension) around the limb. The short stretch bandages do not expand when the calf muscle pump is exercised and the force of the muscle is directed back into the leg which promotes venous return. The limitations of short stretch bandages are that a small increase in the volume of the leg will result in a large increase in compression and this means the bandage provides high compression in the upright position and little or no compression in the recumbent position when it is not required. During walking and other exercises the sub-bandage pressure rises * * steeply and while at rest the pressure comparatively drops. Therefore patients must be mobile * I to achieve effective compression and exercise is a vital part of this form of compression. **** * S ** *

:. Prior to applying bandages, a selected wound dressing is placed immediately over the * *** woundlulcer. The application of a typical four-layer compression bandage system is as *1*I follows: 1. A layer of nonwoven fleece padding bandage is applied with no stretch and 50% overlap, therefore resulting in a double layer. This is to cushion and distribute the pressure, particularly protecting the bony prominences. These padding bandages are generally very soft and comfortable against the skin, as well as being highly absorbent; they therefore absorb any leakage of wound exudates from the wound dressing.

2. A crepe bandage is then applied over the padding bandage which holds the padding bandage in position and smoothens the padding layers. This is also applied with 50% overlap.

3. A long stretch type 3a high compression elasticated bandage is applied over the above two layers. The elasticated bandage is specifically produced to facilitate sufficient compression when applied following the recommended guidelines which are usually stretching the bandage with a 50% elongation and applying with 50% overlap.

4. The final layer is an elasticated stretch. cohesive bandage which is applied with a 50% overlap. This is to act as an overall protective retention bandage. This bandage also applies a degree of compression being classified as type 3a, and it holds the compression bandage in place as well as providing a protective outer-layer. This is normally a nonwoven spunlaid bandage with elastomeric threads.

* I.: The purpose of all types of compression bandage systems is to show good resilience, S.... * .

stability to retain the desirable graduated compression/pressure as well as to maintain this *. * .

compression for about seven days wear and use, which can be sometimes longer as it is dependant on the severity of the chronic leg ulcer being treated. * SI.

* Many patients find the current multi-layer compression bandage system to be S..... * .

inconvenient as well as uncomfortable. Patients have been known to remove and try to reapply bandages themselves to reduce the pain experienced with these chronic venous leg ulcers, which defeats the purpose of the professionally applied compression bandage system.

The four-layer bandage systems are generally very bulky which can reduce a patient's mobility and restrict the choice of clothing and footwear. However, the multilayered bandage systems are uncomfortable to wear due to their bulkiness and undesirable thermophysiological characteristics. They are also aesthetically displeasing and easily soiled.

Furthermore, these multi-layer bandages restrict a wearer's ability to wash and bathe appropriately as they are worn constantly, only being changed once a week. With these restrictions there is the added misery of the ulceration leaking excessive wound exudates which not only adds to the sensation of feeling unclean but all too often also being embarrassed by the malodour/smell of the exudates. Multilayer bandages are also difficult to apply on the limb and are costly due to the requirement for specific bandage types for each layer.

There is therefore a need for a single-layer compression bandage regime that incorporates the ideal performance characteristics of multilayered compression bandage systems, but which eliminates some or all of the problems associated with them as detailed above. No such single-layer bandage that can replace both padding and compression bandages currently exists.

According to the present invention, there is provided a pressure actuator comprising a first fabric layer and a second fabric layer, wherein the first and second fabric layers are * interconnected by threads of a yarn material which maintains a space between the first and second fabric layers, and wherein each of the first and second layer comprise a material S..

having a dtex value from about 95 to about 125. * .**

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: * The dtex value is a unit of measurement for the linear mass density of fibres in a material, and represents the mass in grams per 10,000 metres.

The first and second layers are interconnected and effectively form a single layer compression bandage system, which will be denoted herein as a "3D spacer fabric" or "spacer fabric". This is in stark contrast to the multi-layer and short stretch compression bandages currently used which involve up to four individual layers which are separately applied to a venous leg.

In comparison to traditional woven or knitted fabrics used in existing bandage systems, the range of physical and thermophysiological properties which can be achieved by the 3D spacer fabrics is considerably wider. These structures consist of two independent faces with interconnecting threads joining them back to back. It is the interconnecting threads, or spacer yarn, that creates a space between both the faces of fabrics, hence the name spacer fabric'. The three-dimensional nature of spacer fabrics makes them an ideal device for application next to the skin because they have desirable properties that are ideal for the human body. They can be exceptionally soft, incorporate large volumes of air, and provide good resilience to compression, temperature control, and moisture management. The layer of air that lies between the two independent textile faces creates a comforting, climate-controlling effect which prevents sweating and overheating of the skin. It provides desirable wicking characteristics which help to avoid the build up of sweat and moisture on the skin surface. The relatively open construction provides excellent air circulation but yet with good * thermal insulation. Spacer fabrics also provide an excellent cushioning effect which means * that there is no need to use multiple layers of padding and compression bandages. Also, the **** * ** spacer fabric is lighter than the multilayer bandages. In all, the spacer fabric is more S..

comfortable and relaxing for a person, who is subsequently more prepared to wear the * ..* 5. bandage for the long periods of time required. For venous leg ulcer applications, such * I attributes together with improved elasticity and recovery promote faster healing.

According to one embodiment of the invention, the two layers of the spacer fabric may or may not comprise the same material and can each independently be produced from different fibre types. The material having a dtex value from about 95 to about 125 in each layer may independently be one or more materials selected from, but not limited to, polyester, polyamide, polypropylene, cotton, viscose, lyocell, wool, silk, etc and can have completely different structures.

According to another embodiment, the first and second layers of the spacer fabric may comprise a combination of both a normal natural fibre or manufactured or chemical yam and an elastomeric yarn.

Typically, if each layer contains more than one yarn material, the second material has a dtex value which is lower than that of the first material (e.g. polyester). Typically, the dtex value is from about 35 to about 55, more typically from about 40 to about 50, and still more typically about 45.

A non-limiting example of an elastomeric yam for the second material is a spandex material such as Lycra�, and a non-limiting example of a combination of fabrics which could be used in the layers is polyester and Lycra�.

According to one embodiment of the invention, the spacer yam which maintains a space between the first and second fabric layers is typically a monofilament polyester yarn, which has a remarkable stiffness and provides a higher compression resistance of the spacer 6.06 *6** : * fabric. However, other monofilament spacer yams such as, but not limited to, polybutylene terephthalate (PBT), polypropylene and polyamide (nylon) yarns can also be used.

Combinations of any two or more of these yams may also be used.

These 3D knitted spacer fabrics are durable and reusable products due to their stable, : * compression resistant structure, and also incorporate specific properties such as high volume to weight ratio, softness, breathability and moisture conductivity. Knitted spacer fabrics are generally easy-care and cheaper to manufacture as compared with composite materials and the many different layers of bandages found in the multi-layer compression therapy.

In addition, a single layer compression bandage system in accordance with the invention is easier to apply to a person, is significantly more comfortable for a patient, and above all will be significantly cheaper relative to the two-to four-layer systems currently available.

The two layers, which may or may not comprise the same material or materials, can be engineered and designed independently and separately in different fibres and constructions and, therefore, can possess different characteristics as required. This versatility allows specifically designed materials that can be engineered and developed to suit a wide range of applications.

Typically, the spacer yarn material has a dtex value which is lower than that of the first material (e.g. polyester) in the first and second layers but higher than that of the second material (e.g. the elastomeric yarn material). Its dtex value is typically from about 60 to about 80, more typically from about 65 to about 75, still more typically about 70.

According to one non-limiting embodiment of the invention, the first and second layers can comprise a combination of a multifilament polyester yarn and Lycra�. Even more specifically, the multifilament polyester yarn can have a dtex of about 110 with the Lycra� having a dtex value of about 44. In addition to this, the spacer can have a dtex value of about * 71. * *

:::: According to a further embodiment, when the first and second layers each comprise two yarn materials, the 3D spacer fabric of the invention can comprise from about 45 wt.% to about 55 wt.%, typically between about 47 wt.% to about 52 wt.%, more typically between *. . r about 49 wt.% to about 50 wt.%, of the yarn material with the highest dtex value in the fabric layers (e.g. a multifilament polyester yarn); from about 15 wt.% to about 22 wt.%, typically between about 16 wt.% to about 20 wt.%, more typically between about 18 wt.% to about 19 wt.%, of the yarn material in the fabric layers (e.g. Lycra�); and from about 27 wt.% to about 36 wt.%, typically between about 30 wt.% to about 35 wt.%, more typically between about 31 wt.% to about 33 wt.%, of the spacer yarn material.

According to a further embodiment of the invention, the pressure actuator of the invention further comprises a hydrophilic finish for synthetic fabrics, in the form of a wicking agent. The wicking agent may be, but is not limited to, a non-ionic ethoxylated carboxylic acid compound. One such compound is available under the trade name FERAN ICE from Rudolf Chemie. It could be a polymer resin finish or a silicone co-polymer a hydrophilic silicone elastomeric type of wicking agent.

When a wicking agent is used, it applies a chemical finish to the product which improves the surface properties to permit the product to wick fluid more efficiently. To apply the wicking agent, the product may, for example, be placed in the solution which is diluted to about 20 gIl. The product is in the solution for approximately 30 seconds. Analysis on the product after such a treatment shows that it wicks fluid about 50% more efficiently.

Typically, in use, the pressure actuator of the invention needs to remain in place for up to about 7 days for optimum treatment of a wound. However, according to a further embodiment of the invention, the pressure actuator of the invention does not have any adhesive thereon. This is in contrast to similar existing products which all comprise an adhesive/cohesive layer.

1* The cohesion of pressure actuator of the invention is achieved using FERAN SSF Cone, a S...

: : non-slip silica acid which is also available from Rudolf Chemie. This could also be a non-slip finish of a combination of silica gel dispersions, silica acid and latex polymer; silica acid and acrylates. S.

These can be applied in the same or/and similar manner as described above for the wicking agents.

One example of a typical 3D space bandage in accordance with the invention is given S...

below. * S

Machine Type E20 Interlock Circular Double-jersey machine Dial height = 2-4 mm Yarn Used Feeder 1: 110/3 6F dtex texturised polyester + 44 dtex Lycra Feeder 2: 1 1O/36F dtex texturised polyester + 44 dtex Lycra Feeder 3: 71 dtex (0.08mm) monofilament polyester Feeder 4: 1 10/36F dtex texturised polyester + 44 dtex Lycra Feeder 5: 1 10/36F dtex texturised polyester + 44 dtex Lycra Feeder 6: 71 dtex (0.08mm) monofilament polyester Fabric Properties

Description Grey Finished

Area density (gm2) 350 to 490 370 to 420 Coursespercm 14.5 to 16.5 l4to 15.7 Wales per cm 13.7 to 15 13 to 15 Fabric Content by WeiRht (%) 1 10/36F dtextexturised multifilament polyester yam: 49.6% 71 dtex (0.08 mm) monofilament polyester: 32.2% 44 dtex Lycra: 18.2% * **.* It has been found that the 3D spacer fabric constructions react differently to the S...

* : * . traditional 2D bandages but have many advantages that include, importantly, sustained ::: : graduated compression and uniform pressure distribution around the leg. 3D bandages have * excellent transference of pressure and the sub-bandage compression is not influenced by the *. number of layers as are the traditional 2D bandages. *.*S

* : * Computer modeling techniques have been carried out to model the dimensions and properties of spacer structures, with the variables such as yam type, yarn diameter, fabric structure, plus the fabric properties and specifications, such as tenacity and modulus, being used to determine tenacity, elasticity and Poisson's ratio for the spacer fabrics. From these analyses it has been possible to create a three-dimensional Finite Element (FE) model of a spacer fabric. The computer simulation (FE) model has assisted in the prediction of some of the physical properties and expected performance of wefi knitted spacer fabrics.

As discussed above, a primary potential application for the pressure actuator of the invention is in medical bandages to provide a graduated pressure to a body part such as a leg,

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particularly in the treatment of venous leg ulcers, or in preventing their recurrence. However, other potential applications for the pressure actuator of the invention include, but are not limited to, pressure garments or dressings for persons who have suffered from burns, pressure bandages such as to prevent or treat bed sores, varicose veins or thrombosis, massage bandages, touch interactions for mobile devices and/or virtual reality, body contour correcting garments, pressure suits, knee braces, anti-decubitus devices and bypertrophic burn garments and more. By modifying the pressure to the low range, the bandage can also be used to help blood circulation to ease discomfort for long distance travelers on a train or a plane and prevent potential cases of deep vein thrombosis. Other potential applications for the invention involving the need for a graduated pressure being applied to a body part will be readily apparent to a skilled person and such applications are also envisaged within the scope *... of this invention. * S...

* : * For the sake of convenience and illustration only, reference is made herein to the *:::: present invention in its use in a medical bandage, particularly in the treatment of venous leg *. ulcers. However, it will be apparent to a person skilled in the art that this is not limiting upon **.. the scope of the invention.

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* According to a further embodiment of the invention, pressure sensors can be integrated within the pressure actuator. This can indicate to a person if the pressure being applied by the bandage is sufficient, insufficient, or excessive, and if it needs to be adjusted.

The pressure actuator may comprise pores for ventilation and/or cooling of a patient's body part, allowing for an exchange of fresh air with the outside of the pressure actuator and aiding in moisture control.

According to a further aspect of the invention, there is provided a method of manufacturing a pressure actuator comprising a first layer and a second layer, wherein the first and second layers are interconnected by threads of a yarn material which maintains a space between the first and second fabric layers, the method comprising the steps of: a) providing a first layer of a material; b) providing a second layer of a material which may or may not be the same as the first layer, wherein the first and second layers both comprise a material having a dtex value from about 95 to about 125; and c) interconnecting the first and second layers with a yam material to maintain a space between the first and second fabric layers.

The first and second layers of the pressure actuator may be manufactured using any existing warp and weft knitting technologies and techniques known to a person skilled in the S...

*S*SS' * . *5*S *. According to a further aspect of the invention, there is provided a method of treating

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or preventing the occurrence or recurrence of venous leg ulcers, varicose veins, Deep Vein Thrombosis (DVT) or lymphedema, using a pressure actuator comprising a first layer and a S.....

* second layer, wherein the first and second layers are interconnected by threads of a yarn material.

According to a further aspect of the invention, there is provided a use of a pressure actuator comprising a first layer and a second layer, wherein the first and second layers are interconnected by threads of a yam material in a medical treatment system. Typically, medical treatment the pressure actuator of the invention may be useful for includes, but is not limited to, the treatment or prevention of venous leg ulcer, varicose veins, Deep Vein Thrombosis (DVT) or lymphedema.

The invention will now be described further by way of example with reference to the following examples and Figures which are intended to be illustrative only and in no way limiting upon the scope of the invention.

Figure i shows a schematic diagram of an electronic pressure transference apparatus which can be used in determining the actual pressure a bandage transfers to a person's leg.

Figure 2 shows a fabric extension device used in assessing the materials used in connection with the invention.

Figure 3 shows a schematic diagram of a prototype electronic mannequin leg used to investigate the pressure mapping of bandages.

Figure 4 shows an illustration of a 3D spacer fabric which can be used as a pressure actuator of the invention. *..* e.

* : * . Figure 5 shows an illustration of a 3D spacer fabric which can be used as a pressure *::: actuator of the invention.

* Figure 6 shows a Finite Element (FE) computer simulated model of the spacer fabric * . ., in accordance with the invention. *

* Figure 7 illustrates the breathability of a warp knitted spacer fabric in accordance with the invention.

Figure 8 shows a graph depicting the pressure distribution characteristics of commercially available bandages.

Figure 9 shows a graph depicting the pressure mapping of commercial bandages on the mannequin leg.

Figure 10 shows a graph depicting the pressure transference of spacer bandages (relaxed).

Figure 11 shows a graph depicting the effect of extension on pressure transference of spacer bandages for the Black (1) sample.

Figure 12 shows a graph depicting the effect of extension on pressure transference of spacer bandages for the White (2) sample.

Figure 13 shows a graph depicting the effect of extension on pressure transference of spacer bandages for the White (3) sample.

Figure 14 shows a graph depicting the effect of extension on pressure transference of spacer bandages for the Blue (4) sample.

Figure 15 shows a graph depicting the pressure profile of 3D spacer bandages and commercial bandages on the mannequin leg equipment.

* **** Figure 16 shows a graph depicting the pressure profiles of 3D spacer bandages in *: . accordance with the invention at different percentage stretches on the mannequin leg equipment.

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* Figure 17 shows a graph depicting the pressure transference of padding and spacer 4*.

bandages. *

**S**.

* Figure 18(a) shows a graph depicting a pilot user trial comparison of a two-layer system with padding and a single layer novel 3D spacer system without padding (standing position).

Figure 18(b) shows a graph depicting the pilot user trial comparison of a two-layer system with padding and a single layer novel 3D spacer system without padding (sitting position). In both Figures 18(a) and 18(b), the line depicting the novel 3D spacer system of the invention is that which finishes the graph with the lower pressure value below the knee.

Figure 19 shows a graph depicting the regression of a two-layer system with padding and a single layer novel 3D spacer system without padding.

Examples -Part 1

Materials and Methods Four spacer fabrics identified as Black (1), White (2), White (3) and Blue (4) were used to study the pressure transference at various pressure ranges. Four padding bandages (PB1a to PB4a) recently available at Drug Tariff were also used for comparison.

Pressure Mapping Apparatus

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An electronic pressure transference apparatus (shown schematically in Figure 1) * 1 developed by the inventors was used. The apparatus consists of a wooden platform for * presentation of test specimens, a strain gauge device and an electronic circuit board. A * * pressure pin (9 mm diameter) is attached on to the load beam of the strain gauge and a corresponding hole drilled through the wooden platform. The height of the pressure pin is adjusted so that it protrudes through the hole of the platform by 1 mm.

The specimen is placed onto the wooden platform over the pressure pin and a series of known metal block weights are placed onto its surface. The strain gauge device detects the pressure transmitted through the specimen at each known pressure in increments created by the metal blocks. The amount of pressure absorbed and dissipated within the textile structure and the actual pressure felt immediately below the specimen, i.e. the patient's leg, is determined. The transmitted pressure through the thickness of the specimen is the absolute pressure exerted on the patient's leg.

A fabric extension device (shown in Figure 2) has also been developed by the inventors which facilitates the extension of spacer fabrics at the required length. The pressure transference of spacer fabrics at various extensions was measured utilising this device.

A prototype electronic mannequin leg developed by the inventors was used to investigate the pressure mapping of bandages. The mannequin leg (shown in Figure 3) simulates a lower limb and has definable tibia, calf and anlde regions. It has eight pressure-measuring sensors, of which two (sensors 1 and 2) are positioned at the ankle, three at the calf (sensors 3-5) and three at locations just below the knee (sensors 6-8). The sensors are connected to an electronic board display unit via strain gauges. e I...

*.. . . Results and Discussion * * * Effect of bulk density * * * ** * * * The basic properties of padding bandages and spacer fabrics used in this study are r.

* * . . given in Table 1 below.

Table 1: Basic Properties of Padding Bandages (PB) and Spacer Bandages Sample Thickness (mm) Area density (gm2) Bulk density (gcm3) PB1a Padding 1.2 90 0.07 PB2a Padding 1.4 93 0.07 PB3a Padding 1.5 79 0.05 PB4a Padding 1.4 72 0.05 Black (1) Spacer 3.24 475 0.15 lower the bulkiness. It is one of the important parameters for treating venous leg ulcers because the padding bandage is applied next to the skin around the leg, and it must be capable of protecting bony prominence and imparting comfort and a cushioning effect to the patient.

An appropriate bulkiness would be required to protect the bony prominences in the leg. It is observed in Table 1 that all the commercial padding bandages (PB1a-PB4a) possess essential bulkiness while the space fabrics of the invention registered significantly higher bulk densities, i.e. the space fabrics of the invention have reduced bulkiness. The spacer fabric is a three-dimensional structure and in 3D spacer fabrics, two separate fabric layers are connected at a distance with an inner spacer yarn or yams using either warp knitting or weft knitting route (as shown in Figures 4-7).

Effect of Pressure Transference of Commercial Bandages

S 5..

*S. S..

* The pressure distribution characteristics of commercial bandages are shown in Figure *5. * * u 8. Obviously, none of the bandages provide the desired uniform pressure distribution. It is a..

vital that an ideal padding bandage should dissipate the pressure between 30 and 40 mml-Ig, as exerted by a high compression bandage (Type 3c), uniformly around the limb.

* In order to ascertain the pressure transference of padding bandages exerted by high compression bandage (Type 3c), the mannequin leg was used. The padding bandage was wrapped around the mannequin leg at 50% overlap (two complete layers) without stretching and a high compression bandage (SurePress) was wrapped over the padding bandage at 50% overlap by rotating the leg. The compression bandage was stretched at 50% extension by applying 1 kgf load when wrapping around the leg. It should be stressed that nurses normally apply the bandages at 50% overlap, and at 50% extension for treating the venous leg ulcers.

The pressure developed at the anide, the calf and just below the knee on the mannequin leg and a high compression bandage (SurePress) was wrapped over the padding bandage at 50% overlap by rotating the leg. The compression bandage was stretched at 50% extension by applying 1 kgf load when wrapping around the leg. It should be stressed that nurses nonnally apply the bandages at 50% overlap, and at 50% extension for treating the venous leg ulcers.

The pressure developed at the ankle, the calf and just below the knçe on the mannequin leg was determined from the display unit and the values were corrected using the regression equations. Prior to the measurement, the pressure sensors in the leg were calibrated to the known pressure range of 0 to 300 rnmHg by making use of a sphygmomanometer. The pressure mapping is depicted in Figure 9.

The interpretation of the results is summarised based on the following two major phenomena.

1. A sustained graduated compression, with higher pressure at the anlde which gradually reduces towards the calf and upper calf according to Laplace's Law, aids the *S..

* * * treatment of venous leg ulcers. The graduated compression mainly enhances the flow * : of blood back to the heart, improves the functioning of valves and calf muscle pumps, * reduces oedema and prevents the swelling of veins. * .S* * *

* : 2. A pressure of approximately 3 0-40 ramHg at the anide that reduces to about 15-20 mmHg (50%) at the calf is generally adequate for healing most types of venous leg ulcers. The ideal pressure just below the knee is around 17 mmHg.

It is obvious from Figure 9 that the existing commercially available bandages do not fulfil the requirements of a sustained graduated compression of an ideal bandage system. The pressure measured by sensor 2 at the ankle is very high although the pressure is graduating down to the knee. It is obvious, however, that all padding bandages exhibited relatively lower compression values than the type 3C high compression bandage when applied on its own without orthopaedic wadding below it.

Effect of Pressure Transference of 3D Spacer Fabric Bandages The pressure transference apparatus and extension test rig were used to study the pressure transference of spacer bandages both under unrestrained and stretch conditions. It will be observed in Figure 10 that the pressure transference of different spacer bandages at any one point varies, and it mainly depends upon the structure and fibre content of the material. It is interesting to note that spacer bandages distributed the applied pressure much more uniformly around the leg than the commercial padding bandages. For instance, the White (2) spacer bandage absorbs the applied pressure of 43.9 mmHg and transfers 2 mmHg at one point. In other words, the absorbed pressure of 41.9 mmHg is uniformly distributed * : *.: inside the fabric structure, which is one of the essential requirements for venous leg ulcer ::: treatment. On the other hand, the commercial padding bandage (PB4a) absorbs 43.9 mmHg :. and transfers 35 mmHg at one point (Figure 8). This means that the bandage distributes only 8.9 mmHg uniformly inside the structure. The higher output pressure from the bandage at one *.** * * . point is undesirable and may slow down and/or block the blood flow in arteries.

Figures 11 to 14 represent the pressure transference of spacer bandages at known pressures under extension up to 120%. It will be noticed that increase in applied pressure does not influence the pressure transference at any one point and the variation is marginal in all the samples. This affirms that these spacer fabrics can be used as ideal padding bandages, and by controlling the tension it will be possible to generate the required pressure for the treatment of venous leg ulcers.

Examples -Part 2

Expeninental Methods The experimental program involved the evaluation and comparison of the 3D weft knitted spacer bandage with a selection of commercially available two-layer compression bandage systems. The commercial two-layer compression bandage system consists of a padding bandage and a type 3c compression bandage. The commercial type 3c compression bandages selected for this study can be seen in Table 2. Initially, the commercial nonwoven padding bandage with a 50% overlap was applied, then the type 3c compression bandage was applied after stretching to the recommended elongation to create the desirable sub-bandage pressure and again with a 50% overlap. The 3D weft knitted spacer bandage of the invention *...

* : has been created to possess all the desirable attributes and sub-bandage pressure of the *::: : current compression bandage systems but in a single layer application. The initial * evaluations were again carried out on the mannequin leg device incorporating eight sensors * from the ankle to just below the knee for mapping the sub-bandage pressure.

S

*SS*** * S Table 2: Commercial type 3c compression bandages

Bandage Producer Description

Tensopress Smith & Nephew Warp knitted cotton!viscose blended yarn and (BSN medical) elastomeric yarn.

Setopress SSL international Narrow woven polyamide/cotton and elastomeric blended yarn (with printed rectangle to square guide for recommended elongation/stretch to desired compression) Surepress ConvaTec Crocheted cottonlviscose/polyamide and elastomeric yarn (with rectangle to square guide for recommended elongation/stretch to ascertain the desired compression) The 3D weft knitted spacer fabric was also tested and evaluated for its pressure transference characteristics, because this product is intended to be applied as a single layer and therefore would not require the nonwoven padding bandage that is utilised for the traditional multi-layer bandage compression systems. It is hence important that the single layer 3D weft knitted spacer bandage is capable of distributing the pressure equally and uniformly at all points of the lower limb.

A pilot user study was also carried out in order to initially evaluate and compare recorded sub-bandage compression using Kikuhime sub-bandage pressure measuring devices.

This was done to obtain quantitative data and characteristics of both the newly developed 3D S...

weft fted spacer fabric and a selected commercial two-layer compression bandage system. * S S... * . .

Compression measurements S..

S * ..S * S*

The electronic mannequin leg device developed by the inventors was used to *S*SSI * S determine the pressure mapping of both the commercial two-layer compression bandage system and the 3D weft knitted spacer bandage. Before the test, all the eight electronic sensors were calibrated by using a sphygmomanometer and the Kikuhime pressure measuring device.

Pressure transference measurements The pressure transference was measured on an electronic pressure transference apparatus also developed by the inventors (Figure 1). This apparatus consists of a wooden platform and a load strain gauge and 9 mm diameter pressure pin. The test specimen is placed onto the wooden platform directly over the pressure pin and a series of known weights (known pressure) are placed onto its surface and strain gauge device measures the pressure transmitted through the test specimen.

Pilot user study A pilot users study was carried out on seven healthy volunteers with no known vascular complications or any other known chronic illnesses. Three women and four male volunteers of different ages and sizes were recruited for these trials. The trials were carried out to directly compare the developed single layer 3D weft knitted spacer bandage and one of : the standard two-layer compression bandage systems. The sub-bandage pressure *::: : measurements were made by using Kikuhime pressure measuring device sensors strategically placed on the volunteers' lower limb. Three Kikuhime devices were calibrated in-house prior * ,. to application. First, a commercial needlepunched nonwoven padding bandage was applied to S...

* : . the limb covering the strategically placed Kikuhime sensors. Then the selected type 3c compression bandage was applied (Surepress� ConvaTec), following the recommended elongation and overlap (50%). The sub-bandage pressure readings were recorded in both a seated position with the volunteers' foot placed flat against the floor, and then again in a standing position. This procedure was then repeated with the application of the 3D weft knitted spacer bandage. The procedure was then again repeated after moving the Kikuhime sensors to down the inside of the lower limb. a

Results and Discussion A specially created 3D computer simulated FE model has been used in the design, development and engineering of the 3D spacer fabric during this research program. The predicted tensile properties from the FE computer model in the machine direction of the fabric were compared with the experimental results to verify the model and a reasonable agreement was obtained. These results from, the parametric study of the FE model were utilised to design and develop the 3D single layer weft knitted spacer bandage for the treatment of venous leg ulcers. The results indicated that desirable levels of pressure (compression) would be achieved at a spacer thickness ranging from 1.6-2.9 mm of a weft knitted spacer bandage. The FE computer simulated model also assisted in the ideal selection of yarn linear densities (dtex) and the fabric area density. These results were used to assist in the design and engineering of the 3D spacer. a...

* : The 3D spacer fabric created is of 2.9 m,m thickness, both fabric faces are composed of weft knitted 110/36F dtex textured polyester plus 44 dtex Lycra� yarn, and the spacer yarn is a 71 dtex monofilament polyester yarn (0.08 mm diameter), creating a soft, elastic, flexible light weight 3D weft knitted fabric. *.**

* : . * * The pressure profile ascertained from the mannequin leg equipment for both the commercial two-layer compression bandage system and the single layer 3D weft knitted spacer bandage clearly showed the desirable gradual reduction of recorded pressure/compression (Figure 15). The recorded measurements show average sub-bandage pressure results from relatively high 68 down to 33 mmHg at the ankle but gradually reducing to 29-11 mmHg below the knee (Table 3 and Figure 15). The 3D spacer bandage achieves desirable comparable results at the 37% stretch with results of 33-51 mmFIg at the ankle reducing to 13-16 mmHg below the knee. Therefore, when compared with the two-1' layer commercial compression bandage system, the single layer 3D knitted spacer bandage possesses a desirable pressure profile. Prior to the above pressure measurement, the single layer 3D weft knitted spacer bandages were also tested at different stretch to establish the desirable stretch/elongation required to achieve the required graduated compression from the anide to just below the knee. Figure 16 shows that a 37% stretch meets the desirable pressure profile.

Table 3: Pressure profile of commercial and 3D bandages, determined on mannequin leg equipment Pressure at different sensors (nimflg) Bandage sample/system Ankle Calf Below knee 1 2 3 4 5 6 7 *..., Ideal (3c) compression 30-40 17-20 15-20(50% less profile to ankle) Surepress+padding 30 39 19 21 31 32 13 20 bandage *.S -Tensopress+padding 38 50 13 15 13 36 11 7 bandage Setopress+padding 33 68 18 17 29 40 18 22 bandage Novel knitted 3D spacer 33 51 28 22 21 32 16 13 bandage (without padding) In order to test the stretch and recovery of the developed 3D spacer bandages, BP 1993:XXF method 1, Extension Measurements on Stretch Bandages was employed. The bandages are tested on a specific test rig to a force of 1 kg per cm sample nominal width. The 3D spacer achieved 151% stretch and a recovery of 93%, within the limits of industrial ( I. standards, therefore showing excellent stretch and recovery properties.

The degree of pressure that is transferred onto the leg through the compression bandage is of major importance. It is important that excessive pressure at any one point on the leg is distributed equally and uniformly at all points, especially over vulnerable bony prominences present around the ankle and the front of the leg. The pressure transference measurements taken on the pressure transference apparatus indicate, unlike padding bandage, the commercial spacer fabrics as well as the 3D spacer fabric possesses excellent pressure distribution properties (Figure 17).

The results from the pilot user study (Figures 1 8a, 1 8b and 19) show the comparison of the single layer 3D weft knitted spacer bandage and a two-layer compression bandage system. Figure 1 8a shows the pressure profile of both the single layer 3D spacer bandage and the commercial two-layer compression bandage system measured at standing position.

Similar measurements were also carried out (Figure 18b) in a sitting position. The desired * : trend of sustained graduated pressure from the ankle to the knee is evident in both cases. The ::: sub-bandage pressure readings at the ankle are 40 to 50 mmHg, reducing to 11 to 18 just below the knee.

The existing commercial two-layer compression bandage system are able to provide * **** * * . uniform pressure distribution, but the single layer 3D spacer bandage of the invention is able to provide both uniform pressure distribution and exactly the stipulated sustained graduated compression profile for venous leg ulcer management.

Conclusion

The effective management of venous leg ulcers has been proved to be highly influenced by the appropriate selection of compression therapy. The current recommended r compression therapy involves multi-layer bandage systems. There are some issues with these systems, to do with the comfort and quality of life of the patients; the time consumed in applying the bandages, together with the risk of inconsistency of compression with the application of numerous layers, and additional costs of the numerous bandage layers. It has been shown that the pressure transference of commercial padding bandages varied significantly and that none of the padding bandages investigated satisfied the requirements of an ideal padding bandage.

The physical tests conducted for this study have shown that the single layer 3D spacer fabric of the invention has been shown to provide a significant improvement over the existing two-layer and cumbersome four-layer bandaging regimens currently available, as it provides pressure profiles which satisfy the desirable pressure graduation from the ankle to the knee. It is able to combine the desirable attributes of both the padding and 2-dimensional compression bandages into one composite 3-dimensional structure, while eliminating the * : *.: disadvantages such as high cost, discomfort for a person, and difficulty and time of *::: : application.

The 3D spacer fabrics also have the excellent cushioning and pressure distribution characteristics, dispensing with the necessity for the bulky padding bandage. The spacer * * . fabrics have many other attributes that can be beneficial in this type of application as they are lightweight, non-fraying, and breathable, provide protective cushioning and enhanced thermophysiological properties. The developed 3D single layer bandage system for compression therapy not only simplifies the treatment but also reduces the application time and minimises the possible elements of error during application, not to mention the potential savings in cost, time and materials.

It is of course to be understood that the present invention is not intended to be restricted to the foregoing examples which are described by way of example only.

Claims (25)

1. Claims 1. A pressure actuator comprising a first fabric layer and a second fabric layer, wherein the first and second fabric layers are interconnected by threads of a yarn material which maintains a space between the first and second fabric layers, and wherein each of the first and second layer comprise a material having a dtex value from about 95 to about 125.
2. 2. A pressure actuator according to claim 1, further comprising a wicking agent.
3. 3. A pressure actuator according to claim 1 or claim 2, wherein the first and second layers may each independently comprise the same or different material.
4. 4. A pressure actuator according to any preceding claim, wherein the first and second layers may each independently comprise more than one yarn material. *e*S a

   * * .
5. 5. A pressure actuator according to any preceding claim, wherein the first and second layers also comprise a second yarn material having a dtex value of from about 35 to about 55.
6. 6. A pressure actuator according to any preceding claim, wherein the actuator comprises : from about 45 wt.% to about 55 wt.% of the yarn material having a dtex value from about 95 to about 125.
7. 7. A pressure actuator according to claim 5 or claim 6, wherein the actuator comprises from about 15 wt.% to about 22 wt.% of the second yarn material having a dtex value of from about 35 to about 55.
8. 8. A pressure actuator according to any preceding claim, wherein the actuator comprises from about 27 wt.% to about 36 wt.% of the yarn material which maintains a space betweenthe first and second fabric layers.
9. 9. A pressure actuator according to any preceding claim, wherein the first and second layers each comprise a knitted material.
10. 10. A pressure actuator according to any preceding claim, wherein the material having a dtex value from about 95 to about 125 may comprise one or more material selected from polyester, polyamide, polypropylene, cotton, viscose, lyocell, wool or silk, or combinations thereof.
11. 11. A pressure actuator according to any of claims 4-10 wherein the second yam material is an elastomeric material.
12. 12. A pressure actuator according to claim 11 wherein the second yarn material is a spandex f** material. * .

    *::: *
13. 13. A pressure actuator according to any preceding claim, wherein the yarn material which ** maintains a space between the first and second fabric layers has a dtex value from about to about 80. * .

    * :
14. 14. A pressure actuator according to any preceding claim, wherein the yarn material which maintains a space between the first and second fabric layers is a monofilament yam.
15. 15. A pressure actuator according to claim 14, wherein the monofilament yarn material comprises one or more material selected from polyester, polybutylene terephthalate (PBT), polypropylene and/or polyamide (nylon).
16. 16. A pressure actuator according to any preceding claim, wherein the first and second layers are separated by a space of between about 1.3 mm and 3.5 mm.
17. 17. A pressure actuator according to any preceding claim, further comprising one or more pressure sensors.
18. 18. A pressure actuator according to any preceding claim, wherein the actuator is porous.
19. 19. A pressure actuator according to any preceding claim, wherein the actuator is a medical bandage.
20. 20. A pressure actuator according to any preceding claim, wherein the actuator comprises no adhesive layer.
21. 21. A method of treating or prevention of venous leg ulcer, varicose veins, Deep Vein Thrombosis (DVT) or lymphedema using a pressure actuator comprising a first fabric layer and a second fabric layer, wherein the first and second fabric layers are interconnected by threads of a yarn material which maintains a space between the first and second fabric layers. a... * . I.

    * .
22. 22. Use of a pressure actuator comprising a first fabric layer and a second fabric layer, *::: * wherein the first and second fabric layers are interconnected by threads of a yarn :. material which maintains a space between the first and second fabric layers in a medical treatment system. * a a. J
23. 23. Use of a pressure actuator according to claim 22, wherein the medical treatment relates to the treatment or prevention of venous leg ulcer, varicose veins, Deep Vein Thrombosis (DVT) or lymphedenia.
24. 24. A method of manufacturing a pressure actuator according to any of claims 1-19 comprising the steps of: a) providing a first layer of a material; b) providing a second layer of a material which may or may not be the same as the first layer, wherein the first and second layers both comprise a material having a dtex value from about 95 to about 125; and c) interconnecting the first and second layers with a yarn material to maintain a space between the first and second layers.
25. 25. A pressure actuator, method or use substantially as described herein in the description and drawings.