Indian Journal of Fibre & Textile Research Vol . 3 1 , March 2006, pp. 2 15-229

Contribution of textiles to medical and healthcare products and developing innovati ve medical devices

S Rajendran" & s C Anand Centre for Materials Research and Innovation, The University of Bolton, Deane Road, Bolton BL3 5AB, U K

The application of medical textiles used in woundcare nursing, implants, and healthcare and hygiene products has been discussed. The production and properties of biodegradable polysaccharide fibres obtained from natural sources, such as alginate, chit in/chitosan, collagen, catgut and branan ferulate, have been highl ighted. Speciality medical polymeric fibres used for produci ng wound dressings, bandages and texti le scaffolds for tissue culture have been presented. In addition, the difficulties encountered by elderly people due to venous leg ulcers and a specific research and development programme carried out at the University of Bolton in developing novel padding and compression bandages for the treatment of venous leg ulcers have also been critically discussed. I t is observed that the developed padding bandages meet most of the criteria required for ideal bandages and have excellent pressure distribution property around the l imb over the exist ing commercial padding bandages. The pressure profi l i ng of the novel padding bandages in two-layer, three-layer and four-layer systems has been studied.

Keywords: Compression bandage, Mannequin leg, Nonwoven, Padding bandage, Pressure distribution, Pressure mapping, Venous leg ulcer

IPC Code: Int. Cl .8 A6 l L l SIOO, D04H

1 Introduction Texti le materials play an important and crucial role

in designing appropriate structures for the healthcare and medical industries. There has been a sharp i ncrease in the use of medical text i le products not only in the hospi tal, hygiene and healthcare sectors but also in hotels, homes and other environments where hygiene i s required. With the i ncreasing threat from new strains of bacteria and viruses and the growing problems such as Deep Vein Thermbosis (DVT) and leg ulcers, it is v i tal that newer or enhanced medical devices should be developed to cope up the situation. The demand for medical texti le products i s enormous both in developed and developing countries. The disposable products used i n the operation theatre dominate the market more i n the USA than i n the EU . I t i s forecasted that the demand for disposable medical supplies in the USA wi l l i ncrease by 5 .6% i n 2009 (ref. 1) . I n view of the increase in demand and the fact that medical textiles are associated wi th human health, i n ternational bodies have enforced strict regulations and legislation and

"To whom all the correspondence should be addressed. E-mai l : sr2 @bolton.ac.uk

have also issued guidelines on the use of medical products.

During the past few years, there have been increasing concerns relating to the performance of bandages for the treatment of venous leg ulcers. This i s because the compression therapy is a complex system and requires two or mult i- layer bandages, and the properties of each l ayer differ from other l ayers. I t has been establ ished that the compression therapy by making use of padding and compression bandages i s an efficient treatment for heal ing venous leg ulcers, desp i te surgical strategies, electromagnetic therapy and i ntermit tent pneumatic compression. I n the U K alone about 1 % o f the adul t population suffers from active u lceration during their l i fe t ime. This paper discusses the appl ication of texti le substrates i n developing textile products for medicine and a specific research and development programme for the benefit of sufferers of leg u lcers due to venous disorder. A total of 12 padding bandages were produced during the course of research and development work. Their performance properties were tested, analysed and compared with the existing commercial paddi ng bandages. The paper also discusses the pressure profi l e work, uS1l1g a

2 1 6 INDIAN J . FIBRE TEXT. RES., MARCH 2006

mannequin leg that simulates the real lower l imb, of the best two developed padding bandages and existing Type 2 and Type 3c compression bandages by using two - layer, three - layer and four - layer systems.

1.1 Speciality Medical Fibres

Medical textiles are broadly c lass ified as non­implantable, implantable, extracorporeal devices and healthcare and hygiene products? Fibres used i n medical texti le devices are classified as biodegradable and non-biodegradabl e fibres. Fibres such as cotton, v iscose, alginate, collagen, chitin, chitosan and other protein fibres that can be absorbed by the body within two to three months are called 'biodegradable fibres ' , whereas synthetic fibres, namely polyester, polyamide, polytetrafluoroethylene (PTFE) and polypropylene, which take more than s ix months to degrade and absorb by the body are ' non-degradable fibres' . The defin itions of terms biodegradable and bioabsorbable are not clearly distinguishable and are sti l l vague and controversial . Many authors interchange the terms to express degradation, absorption, bioabsorption and bioerosion.

Alginates are natural polysaccharides that occur i n seaweed. They are salts of alginic acid present i n certain species of brown seaweeds such a s G iant kelp (Macrocystis pyriJera), Horsetail kelp (Lamina ria digitata) and Sugar kelp (Lamina ria saccharina). A lginic acid consists of two monomers, D-mannuronic acid (M) and L-guluronic acid (G). The relati� proportion of mannuroni c to guluronic acid in alginate fibre significantly affects the properties of the end product. The yarn made from alginate has a dry strength comparable with that of viscose, but its poor wet strength makes i t unsuitable for manufacturing texti le materials. Fol lowing the 'moist heali ng' concept, alginate fibre has become one of the most important materials for wound dressing. It i s establi shed that a moist condition is more suitable for wound heal i ng. When alginate dressing absorbs exudate from wound, a je l ly l ike material is formed and a moist environment is created during the course of healing. At the same t ime calcium alginate rapidly releases calcium ions in exchange for sodium ions on contact with blood, which stimulate both platelet activation and blood coagulation to a greater extend. In addition to generating a moist healing environment, alginate dressings faci l itate a h igh absorbency of exudates from the wound.

Chitin is one of the most abundant natural biopolymers that contains amino sugars [poly( 1 ,4,2-

acetamido-2-deoxy-beta dextroglucose)] . Currently, the commercial source of chitin is from shrimp shel ls . Chitosan is the partially deacetylated form of chit in . A sharp nomenclature between chitin and chi tosan has yet to be c learly defined. It consists of two common sugars, D-glucosamine and N-acety l-D-glucosamine. Un l ike most polysaccharides, chitosan possesses a positive charge. The deacetylated amino groups are responsible for the h igh posi tive charge densi ty of chitosan, which makes the polymer soluble in water and reacts readily with a variety of negatively charged materials . The key properties of chitin and chitosan fibres relevant to their biomedical applications include the fact that they are biocompatible, haemostatic, bacteriostatic, fungistatic, spermicidal, antitumor, anticholesteremic, immunoadjuvant, central nervous system depressant and accelerate bone formation and regenerative effect on connective gum tissue.

Collagen i s a protein fibre obtained from bovine skin . It consists of three polypeptide chains arranged in triple-chain hel ix . These triple-chain hel ixes assemble i nto microfibrils and then fibri ls . Col lagen is the principal structural protein in the vertebrate body. The extracel lular proteins of the main connective ti ssues consist of 90% or more col lagen in tendon and bone and more than 50% in the skin. Collagen has an excellent biocompatabi l i ty which makes it a popular choice as a major component of artificial tissue and wou.nd dres.1'ings.3 Col lagen products such as sutures can readily be accepted by body because of their low immunogenicity and this favours the development of a series of fibrous collagen surgical implants that resembles host tissue.4 Synthetic collagen fibres are prepared by using 5-30% polypeptide solution obtained by mixing hexafluoroisopropanol, formic acid and l i thium halide.s

Catgut, another protein fibre of biological origin , is derived from the small in testines of animals mostly sheep or oxen. To obtain catgut the intestinal tracts of cattle, after removing soft tissue and other residues by mechanical and chemical stripping processes, are treated with chromic salt solution. A number of ribbons are obtained and these are twisted i nto bonded strands. Chromic salts are then leached out by a suitable method. The chromic catgut is normally kept in aqueous alcohol or glycerin to prevent i t from drying out. Catgut becomes stiff when dry and this poses problems in handling products made from it . The catgut is mai nly used for producing sutures.

RAJENDRAN & ANAND: CONTRIBUTION OF TEXTILES TO MEDICAL AND HEALTHCARE PRODUCTS 2 1 7

The major fibres used in i mplants are polylactic acid (PLA), polyglycolic acid (PGA) and polydioxanone (PDO). The fibres made from these biopolymers are biodegradable and bioresorbable. The fibres possess good cell, tissue and blood compatibil i ty as well as resistance to steril i sation and sufficient self-stabi l i ty and provide sufficient mechanical as well as physical properties to the texti le structure. The starting point for making PLA i s the sugar found in cornstarch . This i s fermented to form lactic acid . The lactic acid i s then polymerised to form chains, yielding PLA. PGA i s synthesised via a complex process involving the poymerisation of 1 00% glycolic acid. Fibres can be produced ei ther by using a s ingle polymer or by blending a copolymer of PLA and PGA. Varyi ng the proportion of PLA and PGA alters the degradation rate and strength retention time of the fibre. These properties can, therefore, be varied in this way according to the requirements of specific medical applications . During the process of degradation, fibrous connective tissue replaces the degrading i mplant.

Branan ferulate is a polysaccharide obtained from corn bran. I t is composed of monosaccharide residues such as arabinose, xylose and glucuronic acid. The polysaccaharide backbone is substituted with a- l ­arabinofuranoside residues and a-D-glucopyrano­syluronic acid residues. The fibres produced from branan ferulate enhance wound healing.

Superabsorbent (SA) fibres can be made from SA polymers. SA polymers absorb up to 50 times their own weight of water. By comparison, conventional wood pulp and cotton fil ler absorbents absorb only s ix times their weight. SA polymer granulates retain large quantities of l iquid by forming a gel when i n contact with it. Normally, the SA polymers are not used alone but are combined with other materials to form a component capable of absorbing l iquids. SA fibres show many advantages such as high surface area, fast absorption, flexible handle and ease of formation of soft products wi th different shapes to fit the surface of the wound or body. Currently, there are three different ways of making SA fibres: ( i) to f ix SA powders onto or into a fibre substrate; ( i i ) to modify non-SA fibres so as to increase their absorbency significantly ; and ( i i i ) to synthesise polymer so that i t can be spun i nto fibres using normal spinning techniques and then to cross-l ink the fibres formed i n this way. The absorbency of SA fibres is h igher than that of SA powders because the fibres have a l arger surface area.

Compared with powders, they absorb fluids such as blood and milk at a much faster rate and to a very high leve l . Furthermore, when the fibre absorbs body fluid i t does not lose its fibre structure and returns to i ts original form. I t, therefore, continues to function as a good absorbent mediu m after the fluid has drained out.

Carbon is one of the high performance fibres used i n medical and surgical appl ications. Originally, carbon fibres were made by degrading a fibrous organic precursor such as coif. Today, biomedical carbon fibres possessing low strength and high elongation are obtained by pyrolysing polyacrylonitrile (PAN). High elongation PAN-based carbon fibres are relatively easy to handle and faci l itate the fabrication of composite parts. The fibres produced from PAN precursor do not cause t issue reactions and i nstead stimulate the growth of connective tissues, absorb slowly and are noncarcinogenic and non allergenic. These are relatively flexible and are highly absorbent because of their high surface area.

I n addition to wel l-known cotton, viscose and polyester fibres, some special polymeric fIbres have been developed for medical and hygiene applications. Antibacterial synthetic fibres can be produced by bonding the si lver or the combination of si lver w ith either copper or zinc ion wi th the ion exchange group of the fibre.6 Polyester, acrylic and polyamide fibres were made antibacterial by treating with copper compound containing a borate, carbonate or a mixture thereoC Liu et ai.8 produced spun bioabsorbable fibres from a copolymer of g lycolide and levo-Iactide (20:80) for use as reinforcement materials i n orthopaedic i mplants, surgical meshes, braided sutures and vascular grafts. In vivo trials i ndicated that the fibres exhibited a h igh level of strength retention and bioabsorption. Polyelectric medical fibres that help in the treatment of diseases by accelerat ing blood circulation and i ncreasing metabol ism can be obtained by adding polyelectric minerals such as tourmaline i nto the polymer melt before extrusion.9 Tourmaline emits active ions and the fabric made from tourmaline loaded viscose fibres i mpr.oves the health as well as subcutaneous circulation of blood. I O Tourmaline is grounded i nto particles of about 0. 1 5 ,..lITI and m ixed w ith spinning solution and the v iscose fibres with tourmaline loaded are extruded. Polyurethane urea fibres have been synthesised by making use of a long chain diol, diisocyanate and a chain extender. I I The

2 1 8 INDIAN J. FIBRE TEXT. RES. , MARCH 2006

chain extender contains both urethane and urea l inkages. Woven l igaments made from polyurethane urea fibres are suitable for use as temporary l igaments in anterior cruciate l igament i njuries.

1.2 Woundcare Nursing

Wound healing depends not only on medication but also on proper dressing techn ique with suitabl e dress ing materials. Traditionally , the cotton gauze i s used for dressing because o f its good absorption property and soft handle. However, the gauze dressing does not maintain a moist environment to faci l i tate faster wound healing. Moreover, the studies have shown that the gauze allows moisture to evaporate from the wound and also i t adheres to the wound bed causing pain to the patients on removal and requires frequent changing. 1 2 Modern wound dress ings are developed for spec:ific types of wounds such as low­adherent dressings, fi lm dressings, foam dressings, hydrogel and hydrocolloid dressings, antimicrobi al dressings, antiodour dressings and so on. 13 Modern wound dressing i s composed of absorbent layers held between a wound contact layer and a base material . The absorbent layers absorb blood, body fluids and exudate. The wound contact layer is low-adherent and can easi ly be removed without disturb ing new t issue growth. Generally, the material is placed directly over the wound (primary dressing) and covered with an absorbent pad (secondary dressing) and the whole dressing i s retained with a tape or a suitabl e bandage, depending on the location of the wound i n the body. The primary dressing is expected to maintain the wound temperature, moisture level , permits respiration and allows epitheli al m igration. The secondary dressing must not be too absorbent as i t may cause the primary dressing to dry out too quickly.

Alginate dressing, being bioabsorbable and non­adherent can easilY be removed from the wound without causing any discomfort or damaging the newly formed tissuesl4. Any i solated alginate fibres that may become incorporated i nto the granulating tissue would gradually be absorbed. The main drawback in us ing ,"lginate dressi ng i s that, i f al lowed to dry, the dressing may adhere to the woundl5 . Alginate dress ing i s i ncreasi ngly used for the treatment of diabetic foot u lcer. It forms a hard occlusive matt over the u lcer and thus prevents the continuous drainage. l6 Calcic-sodium alginate dressing was uti l i sed in the treatment of pressure sores, bleeding and/or infected vascular u lcers and

reaffirmed the effectiveness of the dressing. 1 7 A study has shownl8 that the lyocel l fibre dressing replaced the alginate dressing for the treatment of chronic wounds. The chemically converted lyocel l was more absorbent than alginate and reduced the nurs ing time and avoided any trauma to new t issue growth. Wright et al. 19 adopted three methods of appl ications by making use of liquid (s i lver n itrate), cream (s i lver sulphadiaz ine) and a dressing coated with s i l ver for heali ng the wound and found that even though the s il ver compounds were effective against bacteria, the s i lver coated dress ing was the most effective against a broader range of bacteria.

The use of b iological dressing i n wound management has also been studied.20 It is a b iosynthetic wound dress ing constructed by making use of a s i l icone fil m with a polyamide fabric partially embedded i nto the film . Collegen i s i ncorporated i n both the s i l icone and polyamide components. The dressing pack comprised of polyamide/polyester i n rope form was impregnated i n 1 5% sodium chloride and an absorbent pad was uti l ised for the treatment of swell i ng and tenderness in the i nguinal area of a woman?l This system of dressing faci l itated wound healing steadily, diminished odour rapidly and promoted the granu lation of wound bed to heali ng with no maceration of the surrounding skin. It also addressed the patient ' s specifi c needs and proved easy to teach to a fami ly member managing the patient' s woundcare at home. Dressings contain ing activated charcoal22 and nanosi lver23 have been developed i n the recent past to manage malodour and infected wounds respectively. Novel wound dressings for managing diabetic foot u lcers have also been developed recently?4

1.3 implants

The major synthetic medical devices currently used as i mplants contain polyester (PET), polytetrafluoroethylene (PTFE), polypropylene (PP) and polyacryloni tr il e (PAN) fibres. However, PET­and PTFE-based materials are commonly used i n vascular prostheses. Yu e t al .25 found that the i ncorporation of absorbable yarns i n the weft of a woven b icomponent vascular graft promotes faster t issue growth by being a loose and porous structure. On the other hand, the absorbable yarns i n the warp do not exhibit this unique surface. A woven graft for the repair of an abdominal and aorti c aneurysm, weakened wall of the aorta between the renal arteries and the bifurcation of the i liac arteries has been

RAJENDRAN & ANAND: CONTRIBUTION OF TEXTILES TO MEDICAL AND HEALTHCARE PRODUCTS 2 1 9

developed?6 This thi n polyester graft fabric has a double wall thickness of less than 0.5 1 mm and can be woven into a seamless tube or a woven fabric sheet can be formed i nto a cylinder and sewn to provide the desired shape. It is claimed that the ends of the graft minimise the formation of gaps between the i mplant and the vessel wall that enhances t issue in-growth and provides a smooth transition for blood flow. It is a common practice to precoat the graft with human blood before implantation to prevent blood leakage. However, elastomeric coating eliminates the need for precloting the prosthetic tube?7 The technique i nvolves the i mmersion of tube i nto water, drain i ng the excess water from the inside surface and coating the i nner walls by making use of a suitable biocompatible elastomer, for example copolyesters. Collagen or gelatin i s also used to coat the graft.

28

I mplants such as prostheses, catheters, shunts and pacemakers have been coated with a mixture of known antibiotics rifampin, monocycli n and novobiocin to i nhibit the growth of bacteria.

29 Elastic graft that possesses w ithstanding abil i ty from the i mpact of stress induced by the constant flow of blood has been developed.30 The yarns used in the graft possess similar elastic i ty to that of a blood vessel . An artificial blood vessel wi th elastic i ty s imilar to human blood vessel is reported elsewhere.3 1 I t comprises composite fibres of a biocompatible polymer in a knitted, woven or knitted/woven structure. A reinforced absorbable osteosynthesis implants are made from fibres of poly-L-lactide and poly-LlDL­lactide for the treatment of bone fractures.3

2

It is known that the Anterior Cruciate Ligament (ACL) is a very i mportant stabil iser of the femur on the tibia and serves to prevent the tibia from rotating and sliding forward during jumping, running and other quick or sudden physical movements. Interestingly, it is the most frequently injured ligament and can be torn at a force of 33N per kg of body mass or 3 .3 times body weight.33 Synthetic materials such as polyester, polypropylene, carbon, etc have been used i n replacing a torn ACL. Carbon fibres with h igh ultimate strength and h igh modulus can be employed to replace damaged l igaments and tendons.34 They have been incorporated in high densi ty polyethylene prostheses that are used i n total knee replacement.35 M ironova36, who i mplanted polyester l igaments i n 262 patients over a period of 1 5 years, has reported a success rate of 9 1 % . Kennedy­LAD®, Gore-Tex®, Dacron®, Leeds-Keio®, Trevira-

hochfest® and Proflex® l igaments are i ncreas ingly used in l igament replacement surgery. 37 The requirements of an artifi cial l igament are extensive and it must have at least three i mportant properties such as h igh tens i le strength, high elongation and right stiffness to match the compliance of a normal ACL.38

I t i s stated that the chitosan can be used for producing artificial skin, artifi cial blood vessels and surgical sutures.39 A biocompatible three-d imensional knitted pile mesh i mplant has been constructed by making use of polypropylene r.1onofilaments for repairing muscle or t issue wall defects.4o

Monofilament mesh constructions are preferred over multifilaments owing to their small surface and avoidance of wicking effect.4 1 Polyamide fibre mesh (Biobrane) was used for culturing human neonatal fibroblasts .42 Recent stud/3 revealed that the Biobrane and Deoderm are effective artificial skin substitutes for the treatment of i ntermediate thickness burns i n children. Some appl ications of mesh grafts on human beings i nclude protection of esophagogastrostom/4, treating a damaged kidney by external splinting or encapsulation45, repairing pelvic peritorium46, replacing membrane covering the brain47

and abdominal wall defects (hernia).48 Polyester, polypropylene and polyester-carbon composite meshes are known for repairing hernias.

1.4 Healthcare and Hygiene Products

Healthcare and hygiene products i nclude both disposable and non-disposable products mainly used in hospitals such as antimicrobial texti les, surgical gowns, surgical masks and gloves, surgical drapes, surgical footwear and headwear, staff apparel, towels, bedding, d iapers, sani tary napkins, tampons, pantie shields wipes, i ncontinence products and so on. A US patent49 described a process for making a highly stretchable elastomeric absorbent structure comprising thermoplastic and cellulosic fibres that can be used for producing diapers, i ncontinence products, sanitary napkins and wipes. A new breathable d isposable femin ine product that l imits s ide leakage of fluid i s described elsewhere. 50 The product consists of three layers in which the inner top layer is made up of polyester and polyethylene fibres and is l iquid and water permeable, the core layer packed with wood pulp, absorbent cotton, polyester and polypropylene is h ighly absorbent and the third layer consists of a 'U' shaped multilayer hydrophobic

220 I NDIAN J . FIBRE TEXT. RES., MARCH 2006

but vapour permeable barrier. The product i s constructed i n such a manner that the fluid moves to the centre of the core rather than to the s ide edges. It is of interest to note that fibres obtained from gellan gum are util i sed for making tampons.5 1 The gum i s obtained from the culture of Pseudomonas elodea bacterium by fermentation. Antibacterial polyester fabrics have been developed by imbuing antibacterial agents into the structure of fibres rather than depositing on their surface for longer durabil i ty and effect.52 It is stated that the efficacy of the finished fabric to arrest the growth of Staphylococcus aureus and Escherichia coli is about 5 t imes h igher than the con ventional materials . Bel iakova et al. 53 discussed the process for preparing antibacterial formulation by the reaction of carboxymethy l starch with trimethylolated melamine in the presence or absence of cupric ions to render cotton fabric antibacterial . Recent research by Vigo et at. 54 discussed the application of polyethylene glycol on polyester/cotton fabrics as antimicrobial agent. It was found that the treated fabrics exhibi ted some degree of resistance against Staphylococcus epidermidis, Brevibacterium epidermidis, Aspergillus fumigatus and Candida albicans. A synergistic system of formulation comprising inorganic chemicals that i nvolve a metal salt of a monocarboxylic acid, a carbamic acid derivative, a chealating agent, a boron compound, a dimethylene siloxane derivative and an alkene polymer has been proved to serve as an effective antimicrobial agent in arresting the growth of several bacteria, fungi and mi ldew.55 Recently , researchers are focused to util i se natural products as antimicrobial agents for imparting antimicrobial activity to texti les. 56. 57 Chitosan treatment on cotton renders antimicrobial act ivity and the treated cotton fabric shows a high reduction rate in the number of colonies.58 Citric aci d and chitosan formulation have been used as an antimicrobial fin ishing agent for cotton.59 Citric acid reacts with hydroxyl groups i n cotton as well as chitosan o r with amino groups in chitosan and forms ester crosslinking or an inter-ionic attraction and this provides antimicrobial activi ty as well as durable press property to cotton fabric.

1.5 Textile Scaffolds for Tissue Culture

It is i ncredible that textiles are used to cultivate different human organs. The h igh-tech research involves the culturing and growing of l iv ing cel ls, taken from human organs on a textile scaffold constructed to a desired 20 and/or 3D shape. Recent

developments in cell culture technique permit the growth of cells in 3D matrixes on shape building supports manufactured from textil e prostheses. These 3D highly porous textile prostheses manufactured from nonwoven fabrics, foams, sponges, or beads offer a 3D surface for cell growth. Nonwoven technologies used for the large scale production of flat sheets suitable for t issue or organ implants i nclude spunlaid nonwovens, staple fiber nonwovens, microfiber fleece, and solvent spun microfiber fleece. The thermoplastic, biocompatible polymers used for implants i nclude resorbable and non-resorbable polymers. Appl ications for such texti le scaffolds include microfiber fleece reinforced tracheal prostheses and biohybrid l iver assist devices. The scaffold generally consists of biodegradable and resorbable fibres which are produced from biocompatible and degradable polymers such as poly lactic acid, polyglycolic acid and polydioxanone. The biomedical polymers should possess good cell, t issue and blood compatibi l ity as well as resistance to steril isation and sufficient shelf stabi lity and provide sufficient mechanical as well as physical properties to the textile structure. The surface of polymers and fibres can be made biocompatible by attaching functional groups such as -OH, -NH2'

-COOH that enhance the hydrophi l i ci ty , cel l growth and favour the growth of adherent cells.60 3D scaffold used in tissue repair can be produced by using knitted mesh containing monofilament or multifi lament polyester yarns . Carbon fibres based scaffold provides the optimal environment for the regeneration of tissue in the hernia, subcutaneous and intra-articular s ites.6 1 3D scaffold of a wide range of thickness and densities can be produced by needle felt technology. The Smith and Nephew-Advanced Tissue Sciences (ATS) technology involves growing carti lage cel ls on 3D

d h . 6ry bioabsorbable scaffold to pro uce uman tissue. ·

Moscow Textile Institute has developed a tissue dressing that combats various forms of skin disease, including some skin cancer.63 A novel text i le structure has been developed that el iminates tissue damage during suturing and helps i n healing tissue while under tension.64 The structure consists of two :,arallel webs of fabric that are l inked by a draw thread in such a way that when the two ends of the draw thread are pulled, the webs are brought together to meet at adjacent edges. This system el iminates tissue damage that occurs i n other methods of suturing. The webs and draw thread can be made of permanent

RAJENDRAN & ANAND: CONTRIBUTION OF TEXTILES TO MEDICAL AND HEALTHCARE PRODUCTS 22 1

biocompatible fibres such as polyester or bioabsorbable materials. Embroidery technology has been used to build scaffold structures.65 It has been employed to design a scaffold structure by taking advantage of the fact that the embroidery structure does not allow relative movement of yarns unlike knitted interlock structures. This reduces the formation of stiffness in the fabric by ingrowing cells and extracellular matrix deposition .66

1.6 Venous Leg Ulcers

It is important that the arterial and venous systems should work properly without causing problems to blood circulation around the body. Pure blood flows from the heart to the legs through arteries taking oxygen and food to the muscles, skin and other tissues. B lood 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 upward direction only. If the valves do not work properly or there is not enough pressure in the veins to push back the venous blood towards the heart, the pooling of blood in the veins takes place and this leads to higher pressure to the skin. Because of high pressure and lack of availability of oxygen and food, the skin deteriorates and eventually the ulcer occurs. M ajor causes of venous leg ulcers are :

• Inefficient or non-functioning of valves in veins, • Inefficient or non-functioning of calf muscles, • Pooling of venous blood i n veins, • Damaged or swollen veins (varicose veins), • B lood clots in veins (DVT), and • Lack of movement such as prolong.ed sitting or

standing, confinement to bed for long periods, etc.

1.7 Padding Bandages (Wadding or Orthopaedic Wool)

Bandages are classified as retention bandages, support bandages, tubul ar bandages, padding bandages and compression bandages. B andages are selected accordi ng to their level of performance rather than their construction. Of all the bandages, padding and compression bandages are utilised for managing the venous leg ulcers.

Padding bandages play a significant role in the successful treatment of venous leg ulcers. A padding of at least 2.5 cm thickness is placed between the l imb and the compression bandage to distribute the pressure evenly at the ankle as well as the calf region. Wadding helps to protect the vulnerable areas of the

leg from generating extremely high compression levels as compared to those required along the rest of the leg.67 Padding can also be used to reshape legs which are not narrower at the ankle than the calf. It makes the limb more like a cone-shape so that the pressure is distributed over a pressure gradient with more pressure at the foot and less at the leg. Generally, the longer a compression bandage system is to remain in place the greater is the amount of padding needed. An ideal padding bandage should meet the following requirements:

light weight and easy to handle; soft and impart cushioning effect to the limb; capable of preventing tissue damage; capable of distributing pressure evenly around the leg; good fluid absorption and wicking properties; comfortable and should not produce irritation or any allergic reaction to the skin on prolonged contact; should tear easily by hand; and should be cheap.

Padding bandages are applied underneath the compression bandage. A typical four-layer compression bandage system comprises padding bandage, crepe bandage, high compression bandage and cohesive bandage.

1.8 Compression Bandages

It has been demonstrated that the compressIOn therapy that includes padding and compression bandages is highly effective and 'gold standard' treatment for venous ulceration68 and the rate of ulcer healing is high. 69 A sustained 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.7o

Compression bandages are mainly classified as elastic and non-elastic. Elastic compression bandages are categorised according to the level of pressure generated on the ankle of an average leg. Class 3a bandages provide light compression of 1 4- 1 7 mmHg, moderate compression of 1 8-24 mmHg is imparted by class 3b bandages and 3c type bandages impart high compression between 25 mmHg and 35 mmHg. The 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

222 INDIAN J. FIBRE TEXT. RES. , MARCH 2006

skin. It must be stated that approximately 30-40 mmHg at the ankle which reduces to 1 5-20 mmHg at the calf is generally adequate for healing most types of venous leg ulcers.7 1

Compression can b e exerted t o the leg either b y a single layer bandage or multi-layer bandages. In the UK, four-layer bandaging system is widely used whilst in Europe and Australia the non-elastic short stretch bandage regime is the standard treatment. In the four- layer system, the first layer is a nonwoven padding bandage that absorbs exudate and protects bony prominences from excessive pressure. The second layer is a crepe bandage which adds absorbency and smoothens the padding layer. The third layer is a light compression bandage that is highly conformable to accommodate a difficult l imb shape. The fourth layer is a cohesive flexible bandage. It applies pressure and is cohesive in nature, which means the bandages stay in place and maintain effective levels of compression for up to one week.

2 Materials and Methods Ten most commonly used commercial padding

bandages were procured from medical textiles companies for testing and characterisation (Table 1). All these bandages were nonwovens. The novel nonwoven padding bandages designed and produced during this research work are given in Table 2. The fibre types and structures of the bandages are also given in Tables 1 and 2. The following test methods were used to characterise the bandages: • British Pharmacopoeia (BP) absorption method72, • Sinking Time73, and • Pressure transference (using an electronic

instrument developed at the University of Bolton) .

2 . 1 Pressure Transference Apparatus

The electronic apparatus (Fig. 1 ), developed at the University of Bolton, consists of a wooden platform for presentation of specimen, a strain gauge device and an electronic circuit board. A pressure pin (9 m m diameter) is attached on t o the load beam o f the strain gauge and a corresponding hole drilled through the wooden platform. The height of the pressure pin is adj usted so that it protrudes through the hole of the platform by 1 mm.

The padding bandage is placed onto the wooden platform over the pressure pin and a series of known metal block weights ranging from 200 g (3 mmHg) to 4 1 00 g (60 mmHg) i n blocks of 200 g (3 mmHg) are

Fig. I -Pressure transference apparatus

Table I --Constructional detai ls of commercial padding bandages

Bandage Fibre type code

PB I Polyester PB2 Polyester

PB3 Viscose PB4 Polyester/Viscose

(40:60) PBS Polyester/Polyolefin

(85: IS) PB6 Polyester

PB7 Pol yester/Vi scose (50:50)

PB8 Polyester PB9 Polyester PB I O Polyester

Structure

Needle-punched (one side) Needle-punched (one side) & thermal bonded Needle-punched (one side) Needle-punched (one side)

Needle-punched (one side) & thermal bonded Needle-punched (one side) & thermal bonded Needle-punched (one side)

Needle-punched (one side) Needle-punched (one side) Needle-punched (one side) & thermal bonded

placed onto its surface. The strain gauge device detects the pressure transmitted through the bandages at each known pressure in increments created by the metal blocks. The amount of pressure absorbed and dissipated within the bandage structure and the actual pressure felt immediately below the bandage (the patient' s leg) is determined. The transmitted pressure through the thickness of the bandage is the absolute pressure exerted on the patient's leg.

2.2 Pressure Profiling Instrument (Mannequin Leg)

A prototype electronic instrument developed at the University of Bolton was used to i nvestigate the pressure mapping of two-layer, three-layer and four-

RAJENDRAN & ANAND: CONTRIBUTrON OF TEXTILES TO MEDICAL AND HEALTHCARE PRODUCTS 223

Table 2-Specifications of novel padding bandages developed at the University of Bolton

Bandage Product Fibre type Structure code

NPB I S ingle Polyester Needle-punched component (both sides)

NPB2 S ingle Polyester Needle-punched component (bleached) (both sides)

NPB3 S ingle Hollow polyester Needle-punched component (both sides)

NPB4 Single V iscose Needle-punched component (both sides)

NPB5 Single Hol low viscose Needle-punched component (both sides)

NPB6 S ingle LyoceJl Needle-punched component (both sides)

NPB7 Binary Polyester/Viscose Needle-punched blend (75:25) (both sides)

NPB8 B inary Polyester/Viscose Needle-punched blend (50:50) (both sides)

NPB9 B inary PolyesterlViscose Needle-punched blend (25:75) (both sides)

NPB I O B i nary PolyolefinlViscose Needle-punched and blend (20:80) thermal bonded

(both sides) NPB I I Tertiary PolyesterlVi scose/ Needle-punched

blend Cotton (bleached) (both sides) (33:33:33)

NPB I 2 Tertiary PolyesterlViscose/ Needle-punched and blend Polyolefin thermal bonded

(60:25: \ 5 ) (both sides)

layer systems. The mannequin leg (Fig. 2) simulates a lower limb and has definable tibia, calf and ankle regions. It has 8 pressure-measuring sensors of which 2 are positioned at ankle, 3 at calf and 3 at below knee. The sensors are connected with an electronic board display unit via strai n gauges. The padding bandage was wrapped around the mannequin leg followed by Type 2 or Type 3c compression bandages for two-layer system, Type 3a and Type 3b for three­layer system, and crepe bandage, Type 3a and Type 3b for four-layer system. All the compression bandages were wrapped around the leg at 50% overlap (two complete layers) by rotating the leg. The compression bandages were stretched at 50% extension by applying I kgf load when wrapping around the leg. However, the padding bandages were applied without stretch. It should be mentioned that the nurses normally apply the bandages at 50% overlap, and at I kgf stretch (50% extension) for treating the venous leg ulcers. The pressure developed at ankle, calf and below knee positions in the mannequi n leg was read from the display unit and the

Fig. 2-Pressure profi le i nstrument (mannequin leg)

NPB12 NPB11 I I

I • Absorption l

I o Sinking Time � -l � NPB10 Q) g> NPB9

u � NPB8 Ol 0) NPB7 c � NPB6 '"

a.. NPB5 � NPB4 z NPB3 NPB2 NPB1

� r-� � � r---"

r--�

,

I I

I I

, - -----,- ,- ----.------- ( I 10 12 14 16 18 20 22 24 26 28

Absorbency (g/1 00cm')/Sinking Time (s)

Fig. 3-Absorption and sinking t ime of novel padding bandages

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 0-300 mmHg by making use of a sphygmomanometer.

3 Results and Discussion

3.1 Absorption of Solution Containing Na+ and Ca++Ions

B ritish Pharmacopoeia method is used to test the absorbency of dressings because it uses sodium and calcium ions, which resembles artificial blood, at body temperature. The method provides performance indicators that are useful to compare the absorbency of dressings. Dressings that absorb less than 1 2 g of liquid per 1 00 cm2 are classified as low absorbency and dressings that absorb 1 2 g per 1 00 cm2 of liquid or more are classified as high absorbency . 72

Fig. 3 shows the absorbency of developed padding bandages tested by BP method and the rate of

224 INDIAN J . FIBRE TEXT. RES., MARCH 2006

absorption tested by 'Sinking Time' method. The absorbency as well as the rate of absorption of commercial bandages is given i n Fig. 4 for comparison. It is in teresting to note that the absorption of developed bandages is signifi cantly h igher than that of commercial bandages, irrespective of fibre types and structures. Most of the commercial bandages require h igher time to sink into the solution and this means that the rate of absorption i s very low, whereas the rate of absorption of all the developed bandages is very high.

3.2 Pressure Distribution of Bandages

Padding bandage i s applied beneath the compression bandage. The degree of pressure that i s induced into the leg by the compression bandage is of

Absorbency (g/10Ocm')/Sinking Time (s)

Fig. 4-Absorption and sinking time of commercial padding bandages

60.00 ��

i -+-PBl

___ PB2

' --6-PB3

so.oo +-------- 1 /II PB4 -I

� 40.00 j -f 30.00

I -lIrPB5

�" '· PB6

-+-PB7

- PB9

I <> PB10

en � a.. '0 � 20.00

::J en ro Q) �

10.00 ·�·

major importance. I t has been demonstrated that too h igh a pressure on the leg not only leads to further complications of venous system but also promotes arterial d isease. I n contrast, inadequate pressure cannot help to heal the venous ulcers. Even if the compression bandage is applied at the correct tension, it is probable that the excessive pressure will be generated over the bony prominences of the leg. Hence, there is a need to d istribute the pressure equally and uniformly at all points of the lower l imb and this can be achieved by applying an effective padding layer around the leg below the compression bandage.

The pressure d istribution characteristics of commercial bandages are shown in Fig. S. UJViously, none of the bandages provides uniform pressure distribution up to 60 mmHg. However, PBS , PB6 and PB8 did distribute the applied pressure evenly only up to around 7mmHg and the efficacy of the even pressure d istribution degrades thereafter. It is vital that an ideal padding bandage should diss ipate the pressure between 30mmHg and 40mmHg, exerted by high compression bandage (Type 3c), uniformly around the l imb.

A significant improvement in d istributing ·the applied pressure of the developed bandages, in contrast to the commercial bandages (Fig. S ) , can be observed in Fig. 6. The bandages N PB 1 , NPB2, NPB3 , NPB4, NPBS, NPB7, NPB8 and NPB9

2.93 5.86 8.79 11.72 14.65 17.58 20.51 23.44 26.37 29.22 32.15 35.08 38.01 40.94 43.87 46.80 49.73 52.66 55.66 58.52 59.99

Applied Pressure (mmHg)

Fig. 5-Pressure distribution of commercial padding bandages

RAJENDRAN & ANAND: CONTRIBUTION OF TEXTILES TO MEDICAL AND H EALTHCARE PRODUCTS 225

50.00

i -- NPB1 l 40.00 , -+- NPB2 E -+- NPB3 .s � NPB4 � -+- NPB5 '" ... '" � 30.00 1 --+- NPB6 ... a:

I

-+- NPB7 ... "0 ... � - NPB8 ... '" ... , '" - NPB9 ... :E 20.00 ... ::!: -- NPB10

.... - NPB11

I ... NPB 1 2 ... ... 10.00 · ...

I ... ... ... ... ... 0.00 .

2.93 5.86 8.79 1 1 .72 14.65 1 7.58 20.51 23.44 26.37 29.22 32.15 35.08 38.01 40.94 43.87 46.80 49.73 52.66 55.66 58.52 59.99 Applied Pressure (mmHg)

Fig. 6-Pressure distribution of novel padding bandages

mmr--------------------------------------------------------

�ilm 1 mil e lfm :s fA :g IIiIiJ ----- -"""-..... �� Ii.

'tI e ; rml co � ail ----.- .----'�--"...,:=-

fIil

Based on C i rcumference

._ --- ---

------ - - .-- --- ---------1

� �--------------------------------� � --....

Bml --.... 1:".:., --....

Fig. 7-Comparison of pressure profile of single- and two-layers of type 2 wi th NPB5

i mparted almost uniform pressure distribution up to the required 30 - 40 mmHg. It is obvious that even after 40 mmHg the pressure d istribution of the entire novel padding bandages, except NPB 1 1 and NPB 1 2, does not degrade significantly up to 60 mmHg.

3.3 Pressure Mapping of Novel Bandages I n order to ascertain the pressure d istribution of

novel padding bandages in two-layer, three-layer and four-layer systems, a prototype electronic i nstru ment (mannequin leg) described in section 2.2 was used. Table 3 shows the pressure profi l ing work carried out using Type 2 short stretch and Type 3a, 3b and 3c compression bandages on pressure profile ins trument (mannequi n leg). The best two novel padding bandages (NPB5 and NPB8 ) developed at the

University of Bolton were used as first layer fol lowed by e i ther Type 2 or Type 3a, 3b and 3c bandages. Figs 7 - 1 0 show the actual pressure measured at ankle, calf and below knee positions after applying single­layer, two-layer, three layer and four-layer bandages. The i nterpretation of the results is summarised based on the fol lowing two major phenomena: ( i ) A sustained graduated compression, h igher

pressure at the ankle which gradually reduces to calf and upper calf according to Laplace' s Law74, aids the treatment of venous leg u lcers.75 The graduated compression mainly enhances the flow of blood back to the heart, i mproves the functioning of valves and calf muscle pumps, reduces oedema and prevents the swell ing of veins.7o

226 INDIAN J. FIBRE TEXT. RES., MARCH 2006

Table 3-Pressure mapping of bandages

• Existing compression bandage (Type 2 and Type 3c) alone (Single layer) Type 2 -Rosidal K and Actiban. Type 3c -Tensopress, Setopress and Surepress.

• Existing compression bandage (Type 2 and Type 3c) plus developed padding bandage (NPB5 and NPB8)

( i ) Two-layer system 100% hollow viscose (NPB5); and 3c compression bandage (Tensopress).

( i i ) Two-layer system 100% hollow viscose (NPB5); and 3c compression bandage (Setopress).

( i i i ) Two-layer system 1 00% hollow viscose (NPB5); and 3c compression bandage (Surepress).

( iv) Two-layer system 50:50 PlY (NPB8); and 3c compression bandage (Tensopress).

(v) Two-layer system 50:50 PlY (NPB8); and 3c compression bandage (Setopress ).

(vi) Two-layer system 50:50 PlY (NPB8); and 3c compression bandage (Surepress).

(vi i ) Two-layer system 1 00% hollow viscose (NPB5); and Type 2 short stretch bandage (Rosidal K).

(v i i i ) Two-layer system 1 00% hollow viscose (NPB5); and Type 2 short stretch bandage (Actiban).

( ix) Two-layer system 50:50 PlY (NPB8); and Type 2 short stretch bandage (Rosidal K).

(x) Two-layer system 50:50 PlY (NPB8); and Type 2 short stretch bandage (Actiban).

(x i ) Three-layer system 1 00% hollow v iscose (NPB5); 3a compression bandage (Profore #3) ; and 3b compression bandage (Profore #4).

(x i i ) Three-layer system 50:50 PlY (NPB8); 3a compression bandage (Profore #3); and 3b compression bandage (Profore #4).

(x i i i ) Four-layer system 1 00% hollow v iscose (NPB5); crepe bandage; 3a compression bandage (Profore #3); and 3b compression bandage (Profore #4).

(x iv) Four-layer system 50:50 PlY (NPB8); crepe bandage; 3a compression bandage (Profore #3) ; and 3b compression bandage (Profore #4).

( i i ) Approximately 30-40 mmHg at the ankle that reduces to 1 5-20 mmHg (50%) at the calf i s generally adequate for healing most types of venous leg ulcers.7 1 The ideal pressure j ust below the knee is around 1 7 mmHg.76

I t is pointed out that the sub-bandage pressure developed beneath the bandage at ankle, calf and below knee regions could be i nterpreted with the theoretical pressure calculated from the circumference of the l imb and also the radius of curvature of the l imb to determine whether the bandage system provides the required graduated compression (higher pressure at the ankle which gradually reduces to calf). S ince the leg is not circular, the pressure exerted by the bandage system varies around the circumference at any given point on the leg particularly over bony prominences such as malleolus (ankle bone) and tibial crest (shin) . Therefore, i t i s appropriate to compare the sub-bandage pressure with the theoretical pressure calculated from the radius of curvature of the l imb. However, the realistic observation would be made when the sub-bandage pressure is compared with the theoretical pressure calculated from the c ircumference of the l imb rather than the radius of curvature because of the fol lowing two reasons : ( i ) One of the main purposes of applying padding

layer next to the skin i s to make the leg a circular­cross section by protecting bony prominences. Compression layer is appl ied only after making the leg c ircular using adequate padding and, therefore, it is more appropriate to compare the pressure developed under the bandage system with the theoretical pressure derived from the circumference of the leg in order to determine graduated compression; and

( i i ) The widely accepted Laplace equation that determines the theoretical graduated compression takes into account the circumference of the l imb and not the radius of curvature.

A brief account of the performance of different two-layer bandage systems is given below : • The sustained graduated pressure d istribution of

two-layer bandages i s superior to s ingle-layer in both Type 2 short stretch (Figs 7 and 8) and Type 3c h igh compression bandages (Figs 9 and 1 0) .

• The contribution of novel padding bandages (NPB5 and NPB8) in distributing sustained graduated compression is substantiated (Figs 7 - 1 0) .

• Both NPB5 and NPB8 performed well with Type 2 and Type 3c bandages (Figs 7 - 1 0) .

RAJENDRAN & ANAND: CONTRlBUTION OF TEXTILES TO MEDICAL AND H EAL THCARE PRODUCTS 227

�r---------------------------------------------------------------�

� ��������������� I ....... � ___ @R:i:C;liAtiFft'3 -.-a.;mm -*-@Q:I:Q'AHi1ffl1 -e-ti mm �------------------------------------------------------------------_; :I:

llml----------------------------i f mm �--��--------------------__ �------------------------------------_; ::l : mm �----�����c_------�������::��------------------------� Q.

� � �--------���������----------������------------------� f ; � �----��------�r_----------------------------��----------------_; ns ;; n\l r-�����=��;;;�������������i=j ml r---

� L-________ --------------__ --------------__ ----------------------� !:imm ----� l:mm:i"44 -------.�

Fig. 8--Comparison of pressure profi le of single- and two-layers of type 2 with NPB8

��--------------------------------------------------------------�

Fig. 9--Comparison of pressure profi le of single- and two-layers of type 3c with NPBS

fmI Ili!!l �

_mil ....... til :I: E mil g � 1ll!1 ::l VI ! 1miJ a.

"C fil'il f ::l VI fil'il ns .. � Ell fli.I III

B!m Blm '=nuiMJ"44

Fig. 1000Comparison of pressure profile of single- and two-layers of type 3c wi th NPB8

228 INDIAN 1. FIBRE TEXT. RES., MARCH 2006

• There IS not much difference In pressure distribution characteristics of NPB5 i n conjunction with Type 2 and Type 3c bandages (Figs 7 and 9). However, NPB 8 performed better with Type 2 than wi th Type 3c (Figs 8 and 1 0) .

• The Type 2 with NPB8 bandage system seems to fulfil the requirements of around 40 mmHg at the ankle, graduating down to about 1 7 mmHg just below the knee (Fig. 8) . However the pressure measured by sensor 2 at the ankle is very high (Fig. 9). This trend is seen almost i n all the bandaging systems (Figs 7 - 1 0) .

• The ankle pressure exerted by Type 2 with NPB5 system is high, although the pressure gradually reduces down to the knee (Fig. 7) .

• The pressure level needs to be reduced considerably at the ankle in Type 3c with NPB5 or NPB8 system (Figs 9 and 1 0) .

It i s observed that there are conflicting trends in graduated compression profi le between two-layer system and three or four-layer system. The pressure registered at ankle, calf and knee i s always h igh in both three-layer and four-layer systems when both NPB5 and NPB 8 are involved.

4 Conclusions A brief overview of the application of textile fibres

and products in various areas of medicine i s presented. It i s demonstrated that the venous leg ulcer i s a severe problem especially for elderly people and hence there is a need for developing novel padding as well as compression bandages to enhance the healing. The study has clearly indicated that the performance and properties of the existing commercial padding bandages varied and none of the bandages investigated satisfied the requirements of an ideal padding bandage. The novel padding bandages developed during this research by making use of suitable fibre types demonstrated that the performance characteristics are superior to the existing commercial bandages. The study revealed that the developed bandages have high absorption and uniform pressure distribution properties. The novel bandages are soft and provide cushioning effect to the leg. A completely new technique has been adopted for the manufacture of these bandages.

The pressure mapping of novel padding bandages i s analysed by making use of pressure profile i nstrument (Mannequin leg). Both short stretch and high compression commercial bandages have been used to

determine the pressure distribution of novel padding bandages at two-, three- and four-layer bandaging systems. The results showed that the two-layer bandaging system that contains novel padding bandages fulfi ll s the requirements of around 40 mmHg at the ankle, graduating down to about 1 7 mmHg just below the knee. However, the pressure registered at ankle, calf and below knee positions is always high in both three-layer and four-layer systems .

Acknowledgement The authors wish to thank the Department of Trade

and Industry (DTI) UK and the University of Bolton for funding the project. The co-operation and support provided by the industrial consortium of Vernon Carus Ltd, UK; Lantor (UK) Ltd, UK; Brightwake (UK) Ltd, UK; Bowling Finishing, UK and John Brierley, UK during the course of research and development work are gratefully acknowledged and appreciated.

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