WOUND HEALING ANDTHEDRESSING* · wound as soon as possible, one should dry the wound... for whatis soonest dried up. . . thereby most readily separates from the rest of the tissue

Brit. J. industr. Med., 1963, 20, 82.

WOUND HEALING AND THE DRESSING*BY

JOHN T. SCALES

From the Department of Biomechanics and Surgical Materials, Institute of Orthopaedics,University ofLondon

(RECEIVED FOR PUBLICATION ON SEPTEMBER 18, 1962)

The evolution of surgical dressings is traced from 1600 B.C. to A.D. 1944.The availability of an increasing variety of man-made fibres and films from 1944 onwards has

stimulated work on wound dressings, and some of the more important contributions, both clinicaland experimental, are discussed. The functions of a wound dressing and the properties which theideal wound dressing should possess are given. The necessity for both histological and clinicalevaluation of wound dressings in animals and in man is stressed.Wound dressings are the most commonly used therapeutic agents, but there is no means whereby

their performance can be assessed. An attempt should be made either nationally or internationallyto establish a standard method of assessing the performance of wound dressings. For this it isnecessary to have an internationally agreed standard dressing which could be used as a referenceor control dressing in all animal and human work. The only animal with skin morphologicallysimilar to that of man is the domestic pig. Three types of wounds could be used: (1) partial-thickness wounds; (2) full-thickness excisions; and (3) third-degree burns.The development of standard techniques for the assessment of the efficiency of wound dressings

would be of considerable benefit to the research worker, the medical profession, the patient, andthe surgical dressings industry.

It could be supposed that by now the medicalprofession should be able to define the propertiesrequired of various dressings; but this is not so.Wound healing is a complex process which is notyet fully understood. It is influenced by manyfactors, not the least important being the localenvironmental factors which can be harmful orbeneficial depending on the properties of the dressing.

It is necessary to examine the history of dressingsin order to appreciate how clinical trial rather thansystematic experiment has until very recently beenthe usual way in which dressings have been investi-gated. The products of the polymer chemist havestimulated research along new lines, and I believethat the synthetic fibre industry must increasinglyinterest itself in wound healing, even though theimmediate reward in terms of weight of fibre andfilm consumed may seem small. Likewise, themedical profession must co-operate more with theindustry ifimprovements in treatment are to be made.

Evolution of Dressings1600 B.C. to A.D. 1944

Blakiston's Illustrated Pocket Medical Dictionary(1952) states that the chief functions of a bandageare "to hold dressings in place, to apply pressure, toimmobilize a part, to support a dependent or injuredpart, to obliterate tissue cavities and to checkhaemorrhage". A dressing is described as "materialapplied to protect a wound and favour its healing".The two terms have been and are used indiscrimin-ately.A wound dressing is still the most commonly used

therapeutic agent, and it is probably true to saythat the foundations of the art and science ofmedicine were laid when early man first treatedwounds. Here we are concerned principally withnatural and synthetic dressing materials, i.e. thosematerials which come into contact with the woundor have an effect on the wound environment.

In the Edwin Smith and Ebers Papyri, which wereprobably written between 1600 and 1500 B.C., thereare frequent references to fabrics used for bandagesand dressings and the importance of certain aspects

82

*Paper presented at the Second World Congress ofMan-made Fibresin London, May 1962, and reproduced by permission of the Comit6International de la Rayonne et des Fibres Synth6tiques.

on February 21, 2021 by guest. P

rotected by copyright.http://oem

.bmj.com

/B

r J Ind Med: first published as 10.1136/oem

.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/

WOUND HEALING AND THE DRESSING

of treatment, for example, the drainage of deep orcontaminated wounds. All manner of medicamentswere applied to the wound, from dung to honey.Hippocrates (400 B.C.), describing the treatment ofa head wound says, "It should not be moistened,nor should it be bandaged; after cleaning thewound as soon as possible, one should dry thewound ... for what is soonest dried up . . . therebymost readily separates from the rest of the tissuewhich is full of blood and life." This sound advicewas not always practised by Hippocrates, who alsoused many noxious agents to stimulate pus, whichwas thought to be a precursor to wound healing.Celsus and Galen (25 B.C. to A.D. 200) believed in theclosed treatment of wounds with the use of abewildering assortment of medicaments to promotepus and wound exudate. The dogma of "laudablepus" persisted into the thirteenth century, when arevolt against this teaching was started by Theodoricde Lucca, a member of the Dominican order inBologna. He wrote, "It is not necessary, as Rogerhas written, as his disciples declare and as allmodern surgeons teach, that pus should be generatedin a wound; no error can be greater than this. Sucha practice hinders nature, provokes disease, andprevents the coagulation and consolidation of thewound (Gordon, 1959). Theodoric's teachings wereaccepted by Henri de Mondeville, surgeon to PhilipLe Bel, King of France, but the forces of traditionwere too strong, and a further 600 years were toelapse before the work of Pasteur was to confirmthe observation of Leeuwenhoek, the inventor of themicroscope, and others who claimed to have seenminute organisms or particles, the existence of whichhad first been suggested by Fracastorius in 1546.

Pasteur showed that fermentation was due to thecontamination of media by micro-organisms andthat these could be killed by heat. If further con-tamination was prevented following sterilization,then putrefaction or fermentation could be pre-vented.

Lister saw the possibilities of Pasteur's findings inrelation to wound infection and believed airborneorganisms to be the cause of wound suppuration.In 1867 Lister described the treatment of 11 cases ofcompound fracture, in which the wounds had beenwashed with undiluted carbolic acid and thendressed with lint or calico and, to prevent evapora-tion, covered by a sheet of tin foil, the forerunnerof the present-day medicated occlusive dressing.Within a few years he had changed to antisepticabsorbent dressings which consisted of eight layers ofcarbolized gauze. He later found that carbolic acid"irritated" the wound, and he sought milder anti-septics, but always his thoughts were to prevent theingress of airborne organisms and to kill by chemical

means those organisms that had gained access to thewound. Lister's teachings, which were slow to beaccepted in England, stimulated thought throughoutEurope. It was soon realized that chemical anti-septics had their limitations and that a more profit-able line of attack might lie in the sterilization of allmaterials coming into contact with the wound.With the development of the steam sterilizer by

Lautenschlager, Schimmelbusch in Berlin was quickto see the advantages of using sterile dressings, andin 1893 he published the results of eight years'successful treatment with steam-sterilized dressings.It was becoming apparent to the more thoughtfulthat the habit of preparing dressings from old linen,rope, and rags was one of the causes of suppuration,and that to reduce cross-infection dressings shouldbe burnt after use and not washed and re-used. Ofthose in the nineteenth century who gave muchthought and effort to improving wound dressings,the names of Anderson of Glasgow, Gamgee ofBirmingham, Mathias, Mayor of Lausanne, Guerinof Paris, and Viktor von Bruns of Tubingen shouldbe remembered. They demonstrated the advantagesof carded, scoured, and bleached cotton wool,compared with materials such as oakum, shreddedand carded old rope from prisons, workhouses, andships, charpie (linen thread), and rag and tow (shortflax fibres).Gamgee's work on wound dressings was un-

doubtedly facilitated by his collaboration withindustry. In a letter to the Editor of the Lancet inFebruary 1880, Gamgee (1880b) reported furtherdevelopments on absorbent and medicated surgicaldressings: "Since you favoured me by publishingmy article (1880a) under the above heading, manycases in the practices of other surgeons, as well asin my own, have proved the perfect comfort andgreat therapeutic value of the absorbent cotton wooland gauze pad with and without antiseptic andstyptic medication. I beg leave through yourcolumns to express regret for sending such scantyspecimens to those gentlemen who have applied tome for the materials. The fact is that such has beenthe demand that it has been impossible to meet it.The difficulty cannot recur as the matter has beentaken in hand by the well-known manufacturingchemists of this town, Messrs. Southall Bros. andBarclay." He went on to say that the suggestion touse pads of Gamgee tissue instead of napkins "hasbeen acted on by several accoucheurs who speak oftheir comfort and purity with approval". This wasthe beginning of the modern sanitary towel. OnFebruary 8, 1880 (Bailey and Bishop, 1946) he gavea lecture at the Queen's Hospital, Birmingham,entitled Absorbent and Antiseptic Surgical Dressings.He stated that "clinical experience has demonstrated

83



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/

BRITISH JOURNAL OF INDUSTRIAL MEDICINE

the great value of absorbent materials. Dischargesdrain through them so rapidly that wounds are keptclean and the surrounding parts dry." According toGamgee, the invention of absorbent dressings was

due to Dr. Mathias, Mayor of Lausanne, but it wasGamgee's idea to combine absorbent cotton woolwith the compressing gauze, and it was he who firstinsisted that the material should be manufactured inan antiseptic manner.

Cotton products, particularly cotton wool, gauze,and lint, became the established dressing materialsand are still the most widely used. During theFirst World War, Wright and Fleming demonstratedthat the antiseptics available did not control woundinfection, partly because they became inactivated bywound exudate and in any case did not penetrate thedeeper parts of wounds. During this period theirrigation of wounds with hypochlorites, Dakin'ssolution, gained favour, while others believed in theexposure of wounds to the air. With improvedtreatment, the problem of adherency of dressingsstarted to emerge. This resulted from the increaseduse of dry dressings and, through the control ofinfection, the diminution of wound exudate, whichin the past had kept the dressing wet and preventedadhesion. It now seemed that a porous non-wettableinter-layer was required to separate the woundfrom the absorbent dressing. Tulle gras, a wide-meshed cotton net, impregnated with soft paraffinwax and balsam of Peru, was introduced by Lumiere.This dressing permitted air to reach the wound, andat the same time drainage was possible. Here was

the beginning of the non-adherent dressing which,with various modifications, has remained popularto the present day. Recently, some manufacturershave replaced the cotton fabric with a rayon tulle.

In 1935, with the discovery of the sulphonamides,a new attack was launched on the problem ofbacterial infection of wounds. These chemo-therapeutic agents were able to kill organisms andcould be administered either locally or systemically.Gradually their limitations emerged, organismsbecame resistant, and the patient hypersensitive.

In Germany, from 1933 onwards, increasingattention was paid to the replacement of cottondressings by paper and cellulose wadding. Researchalong these lines was undoubtedly influenced by theflourishing cellulose industry and a desire to beindependent of cotton, supplies of which were

largely controlled by Britain and America. At thistime the rayon industry was developing, and thesearch for new fibre- and film-forming polymers hadstarted.

In 1943 penicillin was discovered. Once more itwas thought that at last a chemical agent whichwould control wound infection and allow wound

healing to proceed unhindered had been found.Since the Second World War the emergence of awhole range of resistant organisms has once moreblunted the initial enthusiasm.Those who are particularly interested in the history

of wound dressings should consult the very excellentmonograph by Bishop (1959), from which some ofthe information in this introduction has beenobtained.

It is not within the scope of this paper to coverthe physiology of wound healing, about which thereis a considerable literature. Arey (1936) has veryably reviewed some 380 publications on the subject,but it is remarkable that in his comprehensive workthere is practically no mention of the influence ofdressings on the healing process.

Wound Dressing Studies since 1944Natural and Synthetic Fibres and Films.-By 1944

a variety of polymers in fabric or film form hadbecome available.Owens, at the American Association of Plastic

Surgeons in Philadelphia in 1944, drew attention tothe unsatisfactory nature of mesh gauze 44/40 evenwhen impregnated with a non-irritant grease (Owens,1946). Non-impregnated dressings caused pain anddiscomfort, became adherent to the wound and,when removed, caused bleeding and delayed woundhealing. Impregnation of the gauze with a greasybase, in an effort to prevent adherence, interferedwith the drainage of the wound exudate. His firstexperiments, to separate the absorbent dressingfrom the wound, were made with polyamide fabric,but the material used apparently failed in certainrespects which he did not disclose. He found thatnon-delustred 30 denier continuous filament, saponi-fied cellulose acetate fabric, 0 02 in. thick, having awarp and weft count of 114 x 114, caused minimalirritation to the wound, provided adequate drainage,and prevented the penetration of new blood capil-laries into the dressing. Because of the fine weaveand small pore size of the fabric, it is necessary tomoisten it with normal saline to establish capillarydrainage. When the fabric is used on an infectedwound with a thick, purulent exudate, the entiredressing should be moistened, i.e. the fabric incontact with the wound and the absorbent pressuredressing applied over it. Owens' intention was notto produce a non-adherent dressing, but rather to usethe fabric as a separating layer between the woundand the dressing, which would allow drainage but atthe same time keep the wound moist and prevent theingrowth of repair tissue into the dressing. Hebelieved that the use of a smooth, continuousfilament in the construction of the fabric reducedfriction between the dressing and the wound.

84



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


Bloom (1945), when a prisoner of war, used the"cellophane" wrapping from blood transfusionequipment in the treatment of burns and thoughtthat for this purpose it was preferable to tulle gras.The "cellophane" must have been of the water-wettable variety. He stated that "in the more severecases, the area will begin to steam immediately,showing that water is transuding through the dress-ing". Cracking of the film at flexures was, however, adisadvantage, and as a wound dressing "cellophane"has not sufficient plasticity and drape. He notedthat the burns healed normally under a thin layer ofinspissated, purulent serum and that the pain dis-appeared as soon as the burn was covered with thecellulose film. As far as is known, this was the firsttime a synthetic, or perhaps more correctly a semi-synthetic film had been used as a porous woundcover.The first use of a solution of a synthetic polymer

as a wound dressing seems to be that reported in1945 by Marshak. He used a solution of equal partsof isobutyl methacrylate dissolved in toluene as asplint and occlusive cover for full-thickness circularwounds made in the necks of rats and rabbits. Thedry film adhered to the surrounding skin and, untilit was removed on the eighth day, prevented con-traction of the wound. In the animals the solutiondid not produce a vascular reaction or visibleexudate; this was in contrast to man, where he foundthat when the solution was applied to fresh woundsan excessive, sero-sanguineous exudate resulted.There was no reaction when it was applied 24 hoursor more after injury. He stated that "it has beenfound to adhere and protect the wound for three tofour days under conditions (K.P. duty) where abandage dressing was of little value". He suggestedthat the plastic solution might have some practicaluse as a wound dressing, since it did not contractlike collodion, and therefore could be used as anencircling dressing.By this time, non-porous, plasticized polyvinyl

chloride and related polymer films were availableand were being used mainly for first-aid dressings.The dressings carried a cotton-lint pad and had acontinuous-spread adhesive margin. The object ofthis type of dressing was to exclude liquids andbacteria from wounds and to prevent organisms,which might be present in the wound, from con-taminating foodstuffs. This type of dressing is stillthe most suitable for use in the food industry. Thebarrier function of the dressing, of course, is de-pendent on the integrity of the adhesive seal betweenthe dressing and the skin. The principal disadvantageis that, being impervious to water vapour, the hornyor keratinized layer of the skin becomes swollen,white, and soggy. This change in the epidermis or2

outer cellular layer of the skin is due to the uptake ofwater by the keratin. The water is derived from thewound exudate, the normal, insensible loss of watervapour through the surrounding intact skin, and thesecretion of the sweat glands. If the adhesive sealbetween the dressing and the skin fails, then thedressing pad quickly becomes saturated if the part isimmersed in water. With a non-water-vapourpermeable dressing film the pad cannot easily dryout.

In 1944 some significant facts and figures werepublished. Winsor and Burch found that the rate ofwater-vapour loss from the skin was approximately234 g. of water vapour/m.2 body surface every 24hours, the relative humidity of the surroundingatmosphere being 50% at 75°F. (23 9°C.). Therewas approximately a tenfold increase from the floorof a blister raised by cantharides, i.e. 2,340 g./m.2/24hours.

It was shown by Burtenshaw (1945) that the fattyacids of the skin had sterilizing properties. Williamsand Miles (1945) showed that the commonest con-taminating organism of small wounds was Staphy-lococcus aureus, an organism which frequentlyresides in the nose.

Bull, Squire, and Topley (1948) carried outexperiments with a methoxymethyl substitutedpolyamide type 66 polymer. A film 0 001 in. thickhas a porosity to water vapour of 1,920 g./m.2/24hours at 40°C., with a differential water vapourpressure across the film of 53 mm. Hg, or a relativehumidity of 95 %. Taking the figures of Winsor andBurch (1944), such a dressing film has an adequateporosity to water vapour. A major advantage ofthis film was that the porosity did not depend onphysical pores, but rather on the formation of loosechemical bonds between the H+ and OH- ions andthe polyamide. The film could be sterilized and wasan effective barrier to micro-organisms. Studies ofthe bacterial flora of normal exposed skin of hospitalpatients and of skin covered by the polyamide fibredressings showed that Staph. aureus, the principalpathogen in wounds, disappeared and that the num-ber and variety of other organisms were reduced.

Schilling, Roberts, and Goodman (1950) carried outa controlled clinical trial in a Manchester engineer-ing factory, using 0-003 in. thick polyamide filmdressings and polyvinyl chloride waterproof occlusivedressings of the type approved by the Chief Inspectorof Factories. The trial was carefully planned andconducted so as to reduce personal bias to a mini-mum, a most important point in any trial of wounddressings. As the polyamide film was transparent,these dressings were not disturbed until healing tookplace, while the waterproof dressings were changeddaily after the first three days. The wound was

85



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


deemed to be healed when the worker could beallowed to return to his job without a dressing.One hundred and forty-five wounds were treatedwith polyamide dressings and 129 with waterproofdressings. In the final analysis only those caseswere included in which the injury was thought to behealed on a working day other than a Monday.Healing times were as follows: polyamide film,6 04+ 0-16 days; and waterproof dressings, 8-39 +0-25 days. They noted that wounds contaminatedwith oil appeared to heal more quickly than cleanwounds. The polyamide dressings did not carry a

pad, whereas the waterproof control dressings carrieda lint pad. Whether the pads were medicated is notstated. To protect the dressings a cotton bandagewas applied. The results of this trial suggested thatfor minor injuries it was preferable to use a water-vapour permeable dressing. It must be rememberedthat the polyamide film was also permeable tooxygen and carbon dioxide, and this fact may havesome bearing on the results. It was claimed that itwas an advantage for the dressing to be transparent,so that the condition of the wound could be seen,thus obviating unnecessary changes of the dressing.One of the functions of a dressing is to protect

the wound from further injury while it is healing,and for this purpose, particularly with first-aiddressings, a pad is required between the film and thewound to act as a shock-absorber. However, recentclinical trials which we have been carrying outsuggest that there is considerable friction betweenthe pad and the wound in those situations wheremovement occurs, for example in the treatment of aninjury of a joint; the protective advantage may beoffset by the trauma due to friction between the padand the wound.

It may be that the use of a smooth polyamide filmin contact with the wound instead of a lint pad was a

contributory factor in the reduced healing time ofthose wounds treated with this film. The polyamidedressing, however, never became accepted in clinicalpractice since the film lacked drape and extensibility,was difficult to coat with adhesive, and, when theprotective layer over the adhesive was strippedback, the film tended to curl. Further, the polymeris expensive, and this aspect of wound dressings isimportant when they are to be used for other thanexperimental purposes. In spite of these criticisms,however, the work with the polyamide dressing wasthe first well-controlled trial of dressings to bepublished, and was an important step forward inthe evolution of wound dressings.

In 1947 Blaine examined an absorbable alginateproduct, calcium alginate. Calcium ions will reactwith the soluble sodium salts of alginic acid to forminsoluble calcium alginate. Using this reaction,

filament films and foams can be produced. Calciumalginate is absorbed in the tissues, and thus it wasthought that fabrics made of this polymer might beuseful for wound dressings and for operation swabs,which from time to time are left inadvertently in thepatient. A further advantage of alginate productsis that they can be sterilized by autoclaving. Theirrate of solubility can be adjusted by varying thesodium ion/calcium ion ratio during coagulation ofthe sodium alginate. In contact with bleeding tissuescalcium alginate has a haemostatic effect, possiblydue to the release of calcium ions. When calciumalginate fabrics or wool are applied to a wound,dissolution of the structure occurs in the clot, butwhen drying of the scab takes place a hard mass isformed in which are incorporated the threads fromthe unaffected fabric. Only when the wound is wetcan the unaffected part of the dressing be removedwithout causing further trauma. This trauma can beprevented when the central mass is moistened with5% sodium citrate. It has been suggested that the useof a soluble dressing might be an advantage in that,in the early stages of healing, medicaments would bereleased into the wound. Frantz (1948), using calciumalginate in the form of stockinet gauze, found thatwith rats and dogs its haemostatic effect was not asgreat as that ofhuman fibrin foam, oxidized cellulose,and gelatine sponge. He further thought that it wasslightly more irritating than oxidized cellulose. Atthe present time non-medicated, non-absorbablesterile dressings are preferred.For many purposes an important function of a

wound dressing is its ability to absorb woundexudate. This function is dependent on the rate atwhich the exudate soaks into the dressing and thequantity of exudate which it can absorb. The firstfunction is particularly important when the fabric isbeing used as a pad on an adhesive dressing, since, ifblood is not absorbed quickly, it spreads over theskin to which the adhesive is to be applied. The rateof absorbency may be measured by the sinking testfor absorbency described in the British Pharma-ceutical Codex (Pharmaceutical Society of GreatBritain, 1959). In this test 1 g. of the material iscompressed to a volume of about 20 ml. and placedlightly by means of forceps on the surface ofwater at 20°C. It should become saturated and sinkwithin 10 seconds. This test is of value as a labora-tory test for the comparison of fabrics, but theviscosity and other properties of wound exudatesare variable, and therefore the test cannot indicatethe behaviour of fabrics in actual use. Further workis required on this point.The second factor, which is probably of greater

importance, is the quantity of wound exudateabsorbed. This, Savage, Bryce, and Elliott (1952)

86



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


have defined as the water-retention coefficient of thedressing. They studied the water-retention coefficientof a number of materials, including sphagnummoss, muslin, gauze, lint, rayon, and cotton wool.They found that the water-retention coefficientdepended very greatly on the working pressure onthe dressing, that is the pressure applied by thebandage or cover over the dressing. It was foundthat the more random the arrangement of the fibres,the greatest disarrangement being in the wools, thegreater the fluid uptake. Sphagnum moss had thehighest water-retention coefficient, followed bycotton and rayon wool. These were followed bypaper pulp, cellulose wadding, lint, and opengauzes of the B.P.C. and hospital qualities common-ly used in Britain. The finer gauzes used in othercountries were even less satisfactory. Lint, a dressingmaterial peculiar to British countries, had the highestwater-retention coefficient of any woven fabric, thevalue being largely dependent on the proper raisingof the lint. They also studied the pressures producedby a bandage on a dressing. In the experiments, toreduce variables to a minimum, one person appliedthe various bandages over a small rubber pressurebag attached to the arm. An open-wove bandageapplied on a relaxed bare arm, held in a flexedposition, produced pressures varying from 19 to33.5 g./cm.2 When the arm was extended and themuscles tensed the pressures were doubled. When apad of cotton wool was introduced between the skinand the bandage, pressures ranging from 12 to 20g./cm.2 were produced, which were again doubled whenthe arm was extended and the muscles tensed. Usingan elastic bandage ofthe crepe type, average pressuresof 24 g./cm.2 were recorded. On extending the armthe pressure values rarely increased by more than50%, this being due to the elasticity of the bandage.These studies, besides having an important bearingon the water-retention coefficient, once again showhow high friction values may be produced betweenthe wound and the dressing.

Heifetz, Lawrence, and Richards (1952) andHeifetz, Richards, and Lawrence (1953) studied theinfluence of gauze dressings on wound healing in therabbit and in man. Full thickness wounds, 3 x 3in.(7-6 cm.), were made in the abdominal wall of rabbitsand covered by 12-ply 20 x 20 mesh gauze pads.Comparable wounds were made in another set ofanimals and left uncovered. The dressings wereretained in position by elastic adhesive tape.Whether or not the use of the tape made the dressingvirtually of the occlusive type is not clear in thereport. Macroscopically there was no difference inthe appearance of the two sets of wounds until thefourth day, when the covered wound showed atendency to be moist and encrusted. On the eighth

day, however, histological preparations showed thatthere was increased epidermal proliferation in thedressed wounds. In their experiments in man, 53non-infected surgical wounds were divided intothree groups. Normal gauze dressings, abdominalpad, and tape were used in one group, in a secondgroup the same dressings were used but were re-moved at 24 hours, and in the third group no dress-ing was employed. There was no statistical differencebetween bacterial counts in the three groups ofwounds carried out on the first, second, and fourthpost-operative days. While such dressings may notkeep bacteria out, they do drain a wound and removeorganisms and culture media from the wound.They recommended dressings: (1) after an operationin which local anaesthetic agents have been used;(2) for wounds requiring drainage; (3) for woundsthrough the scar of a previous operation; (4) forwounds in which there is not complete haemostasis;(5) for wounds in which tissues have been roughlyhandled; (6) when wounds are closed by catgut;(7) when wounds are closed quickly because of thecondition of the patient; (8) for wounds in whichthere is a dead space; and (9) for wounds requiringsplinting or which might be subject to trauma. Ifexudate resulting from infection and tissue damageis likely to ensue following an operative procedure,then an absorbent dressing which presents a largeevaporative surface and, at the same time, exerts asuction gradient outwards, is required.

In vitro experiments by Lowbury and Fox (1953)with Staphylococcus pyogenes and aureus, Pseudo-monas pyocyanea and micrococci suspended in horseserum showed that after drying there was a drop inthe viable count of all the types of organisms,Ps. pyocyanea being most susceptible.

Korlof (1954) studied the effects of different typesof treatment on wounds in animals infected withPs. pyocyanea and confirmed the beneficial effects ofcooling and drying. Standard burns were made onguinea-pigs and inoculated with Ps. pyocyanea. Thegeneral condition of the animals, their weights,and the healing of the wounds were studied. Elevengroups of 12 male animals were used. A standard25 mm. diameter burn was made. The coagulatedtissue was immediately cut away and the woundinoculated with 0-1 ml. of a 1 : 1,000 dilution of a24-hour broth culture of Ps. pyocyanea recoveredfrom a patient. Some wounds were covered with adressing consisting of a single layer of 3 mm. meshgauze impregnated with vaseline and a layer ofGamgee tissue which was covered with oiled cottonwool followed by an elastic bandage. The dressing,for all practical purposes, could be considered anocclusive dressing. The Gamgee was impregnatedwith one of the following medicaments: polymyxin

87



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


B, chlorophyll, "phenacetol-septon", and sodiumchloride. One group had what was termed a lightporous dressing applied. This dressing consisted ofone layer of oiled 3 mm. mesh gauze, a layer ofGamgee and chlorophyll, and an elastic bandage.In another group the burns were left exposed to theair. The lowest mortality rates were in those groupsin which the wounds were treated with a light dress-ing or were left exposed. While Ps. pyocyanea wasrecovered from all the wounds, the organisms wereless abundant in the burns left exposed. Thecondition of the animals, judged by variation inweight, showed that only with the exposure treatmentdid the animals regain their original weight in 10 to12 days, whereas with all other methods of treatmentthe pre-operative weight had not been regained in30 days.Another approach to the problem of adhesion of

a dressing is the interposition of a non-wettablemacroporous plastic film between the absorbent andthe wound. Gelinsky (1954) described a dressing,consisting of a woven non-absorbent plastic film,backed by an absorbent. Unfortunately, no detailsof the dressing have been given. He claims that thesmooth surface of the dressing reduces surfacetrauma. Gelinsky believes that all dressings are anecessary evil and that it is preferable to expose thewound, but at the same time to keep it slightly moist.Rice and Vogt (1955) used a 00025 in. polyesterfilm, having 200 perforations/in.2; the diameter of theperforations varied between 0-008 in. and 0 04 in.This film was backed with an absorbent. Thecombination of film and absorbent is known as theTelfa dressing. A variety of traumatic and surgicalwounds were dressed. Although no control experi-ments with conventional dressings were reported,they thought that the dressing kept the wounds atleast as dry as conventional dressings. In the presenceof wound infection the perforations were not largeenough. In certain wounds with considerableserous exudate because of adhesion, moistening ofthe dressing was required before it was removed onthe fourth day.Gray and Jones (1956) used a similar type of

dressing as an intranasal pack. Thirty-two patientswere treated, 16 with the polyester film dressingand 16 with vaseline gauze. In none of the 16 caseswas there adhesion of the pack, visible disturbanceof the tissues, or complaints of pain. These findingscontrasted with those in which vaseline gauze hadbeen used. Fourteen patients had some bleeding oradherence of the pack, four patients had a firmlyadherent pack which took from one to three daysto remove, and in one case cartilage and mucousmembrane were dislodged. The disadvantages of theTelfa dressings were that the packs were easily

dislodged and would not pack into nooks andcrannies; in other words, they were too slippery andlacked flexibility.

Gillman, Hathorn, and Penn (1956), using apolyester film absorbent dressing of the Telfa type,found that in full-thickness wounds made in theflanks of rabbits, both epithelial proliferation andrepair of the deeper tissues were delayed whencompared with control wounds dressed with tullegras. Why the apparent difference between man andthe animal?

In further studies, Gillman and Hathom (1957)found that with full-thickness wounds in rabbits anon-perforated film promotes epithelial growth butsuppresses granulation tissue formation. No detailsare given as to the type of polymer. It could be thatone of the factors responsible for this strangedifference between the polyamide film dressing andthe Telfa dressing is the lower wound temperaturethat could be expected with the polyamide dressing.On the other hand, it may that the type of poly-amide used in this work was permeable to watervapour and that the environment beneath the dress-ing was more suited to epithelial proliferation.Although the type and severity of wounds vary

widely and the dressings may be required for avariety of reasons, the various studies of wounddressings have made it possible to specify the pro-perties which the "ideal" all-purpose wound dressingshould possess (Scales, 1954).

1. It should have a high porosity to water vapour,preferably at least 1,400 g./m.2/24 hours, measuredat 37°C. with a relative humidity of 75% (P.A.T.R.A.1948, tentative standard method).

2. It should not adhere either to blood clot or togranulating surfaces, nor should it allow the pene-tration of capillary loops. It must, however, absorbfree blood or exudate and give "protection" to thewound.

3. It should be a barrier to the passage of micro-organisms.

4. It should be capable of following the contoursaround a joint during movement, for example, flex-ing of a finger.

5. It should be unaffected by domestic or industrialfluids, for example, detergents and oils.

6. It should not produc_ a tissue reaction whenapplied to normal skin or granulating surface, nora state of allergy or hypersensitivity.

7. It should be non-inflammable.8. It should be capable of being sealed to the skin.9. It should be capable of being sterilized.10. It should be available at a low cost.In an attempt to meet the above criteria the

Medical Research Council assisted work atStanmore aimed at developing a micro-porous

88



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


water-vapour permeable dressing which would beparticularly useful for the treatment ofminor injuries.The function of this dressing was to create a suitableenvironment for healing to occur; to protect thewound from injury while healing was occurring;to absorb exudate; and to prevent infection of thewound. This development was made possible onlyby close collaboration with industry. Following anumber of clinical trials, an adhesive, micro-porous,plasticized polyvinyl chloride film dressing, carryinga cotton stockinet pad, was developed, which wentsome way towards meeting the criteria for an idealdressing. This dressing, now known as Airstrip,allows the passage of 1,400 to 1,800 g. of watervapour/m.2/24 hours at 37°C. with a water-vapourpressure gradient across the film of 46-6 millibars.

Clinical trials carried out with this dressing, usinga standard polyvinyl chloride waterproof occlusivedressing carrying the same type of pad as a control,showed that there was a considerable reduction inthe bacterial count on normal skin covered by theporous dressing at the end of three days. In thetreatment ofwounds, no Staph. pyogenes was isolatedfrom any wound swabbed initially or at any timeduring healing in those cases treated with the porousdressing. It was recovered from five cases treatedwith the occlusive film dressing. In 18 finger woundstreated with the micro-porous dressing the averagehealing time was 4-1 days, whereas in 15 woundstreated with the occlusive dressing the averagehealing time was 6-3 days (Scales, Towers, andGoodman, 1956). While this dressing allowed thedrying of the wound, this advantage was partiallyoffset by the adhesion of the pad to the wound. Thiswas particularly evident in those areas of the bodywhich did not get wet. In the case of occlusivedressings, which prevented drying, the advantage ofminimal adhesion was offset by undesirable bacterio-logical changes. The problem of adhesion is greatestin the abrasion or graze, where there is an area ofepidermal loss.Baron (1956a), in an extensive series of animal

experiments starting in 1948 using standard ringwounds, studied the effects of various types ofcotton, rayon, and wool woven and knitted dressingson partial- and full-thickness wounds. The outlineof the wound is marked by two concentric blades,the depth of the wound being governed by the depthof the tissue dissected out between the two ring cuts.In his full-thickness wounds, bridges of connectivetissue are left between the central island and thenormal skin. He assessed the influence on healingof these materials by measuring the rate of reductionin area of the wound and by the change whichoccurred in the central island. He has not beenparticularly concerned with the histological and

bacteriological aspects of the problem. In thewounds in which there was minimal loss of fibroustissue, i.e. partial-thickness wounds, there was nooedema of the wound edges, no gross exudate,infection or tissue loss, and wound healing occurredby the end of the second week. In full-thicknesswounds not treated with dressings with 90% tissueloss, the remaining 10% being the fibrous tissuebridge, lying in a cranio-caudal direction (head-tail),the results were very different. After 24 hours therewas considerable oedema of the wound edges, withexudation under the scab. Subsequently, woundinfection occurred with loss of tissue in the centralisland, 20% of which finally became necrotic. Atthe end of the second week there was granulationtissue in the floor of the wound which became coveredby epithelium after 18 to 20 days. If the wounds witha 90% loss of tissue were treated with an eight-layer gauze dressing, necrosis of the central islandoccurred in only 5% of the wounds. When the un-dressed wound was covered with a cellulose film, apurulent wound secretion with oedema of thewound occurred. However, if eight layers of gauzewere applied, only a serous exudate resulted withoutwound oedema. Baron found that "cellophane"dressings delayed wound healing when comparedwith the gauze dressings. He believes that suction,absorption, and compression must all act simultane-ously, and this can be achieved only by the use offabrics, the degree of the beneficial effect dependingon the construction of the fabric and the number oflayers used. To protect the wounds on the guinea-pig, he used bilateral Perspex cups held in place byencircling elastic bands. In some of his experimentshe studied the effects of occlusion by not perforatingthe cups; in this way he created what he called the"moist chamber" effect. As a result of his work hedevised a dressing having a duplex construction inwhich the warp thread is highly twisted, whereas theweft thread is not highly twisted but of substantialbulk. This dressing is made from bright rayon staplefibre. The weave of the fabric is relatively coarse toallow ventilation of the wound and the passage ofwound exudate. This dressing has a relatively highvolume uptake, and, after the dressing is wetted bythe exudate, the highly twisted fibres contract andtend to lift the dressing clear of the wound. Baronstresses the effects of gravity on tissue and exudate,which gravitate to the most dependent part of thewound, and states that compression dressings pre-vent such an occurrence. Ring wounds dressed withbleached cotton dressings healed more slowly thanthose dressed with rayon. He believes (Baron,1956b) that optical bleaches, a number of whichhave been used on wound textiles in Germany, areharmful. The British Pharmaceutical Codex 1959

89



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


does not permit the use of optical bleaches in wounddressings.Baron summarized his work as follows: 1. The

material from which a dressing is made has a decisiveinfluence on wound healing; 2. rayon is preferableto cotton because it has more rapid absorption andis less irritative to the wound, as judged by theamount of exudate and healing rate; 3. thickeryarns are more satisfactory than thinner yams;4. generally there is a lower mortality rate in guinea-pigs with rayon dressings than in those with cottondressings; and 5. a wound dressing should beapplied as soon as possible after injury.

Gelinsky (1957) has somewhat different views fromBaron. He has stated that Baron's work can only betaken as an indicator of the approach to the problemin man, since his method of holding dressings inplace by capsules secured by elastic bands is liableto cause interference with the blood supply to thewound. It is for this reason that Baron has foundhis thick dressings more favourable, because theyallow the "edge pressure" of the capsule to be moreevenly distributed. Gelinsky believes that the highmortality rate with cellulose film was the result ofusing a film only 0 1 mm. in thickness. Gelinsky,however, agrees with Baron on the importance ofwound drainage. He believes that a dry dressing isrequired for haemostasis, and that after six to 24hours the dry dressing should be discontinued as itpromotes a viscous bulky secretion; if a dressing isrequired after this time, it should be of such aconstruction as to keep the wound in a "moist"condition, that is, it should prevent excessive dryingout of the wound. In this way the white cell layer isnot desiccated. The type of dressing which he prefersconsists of a woven or perforated plastic film with afibrous absorbent backing.

Hoffmeister (1959) compared 16 layers of hospitalgauze with one layer of Texatraum (Baron's dress-ing) in the treatment of clean surgical wounds. Twogroups, each of 200 patients, were treated. Thedressings were changed at five days and thereafterat three-day intervals. There were eight cases ofwound infection with the hospital gauze and fivecases with Texatraum. Further, Baron's dressingcould not be classed as a non-adherent dressing.

Solution and Spray-on Dressings.-Since 1952 anumber of reports have appeared concerning theadvantages and disadvantages of film-formingpolymers which can be applied with a swab or as anaerosol spray directly to the wound. It is probablymost convenient to consider this type of dressing asa rather special entity. Their place in wound treat-ment has now become very much clearer.Olow and Hogeman (1953), reporting on an

acrylic resin solution, Nobecutane, found that thepermeability of a 100 , film (0-1 mm.) to watervapour was of the order of 140 g./m.2/24 hours at32°C. To apply a film of consistent thickness is, ofcourse, very difficult, and either too thick or too thina film, with small pores in it due to bubbling andevaporation of the solvent, can easily occur. Theyfound that the solution had self-sterilizing properties.They studied in rabbits the healing rate of aseptic

sutured wounds, aseptic open wounds, and third-degree burns treated with the polymer dressing alone.They compared the healing rate of the sutured andopen wounds with similar wounds treated withgauze dressings, while in the case of the third-degreeburns the control wounds were left undressed. Thedetails of the gauze dressing are not given. Withthe aseptic sutured wounds they found little differencein the rate of healing on either side, except that theepithelium on the side treated with the plasticsolution was possibly slightly thinner than thatfound under the gauze dressing. The tensilestrength of the wounds dressed with the polymerappeared to be about 15% lower than in the woundsdressed with the gauze. There was no evidence ofinfection under the plastic film, whereas under thegauze they found a membrane consisting mainly ofwhite cells, covering almost the entire wound.With third-degree burns no difference in the rate ofhealing could be demonstrated. However, in clinicalpractice they found that, when treating skin-graftdonor sites, it was difficult to maintain the sealbetween the film and the skin because of bleeding,whereas with bums there was an accumulation ofexudate under the film and subsequent infection.

Wallgren (1954) reported on bacteriological studiesand clinical trials with Nobecutane. He found thatthe solution was sterile and that a film could beprepared, the thickness of which he did not state, onculture plates which would prevent the passage ofmicro-organisms. He used the polymer as the onlydressing in 1,500 operations on children up to 15years of age. The dressing was applied to the bodyeither by means of a swab or from an aerosol can.There were no cases of infection or delayed healing.He found that in the treatment of skin-graft donorsites and burns it was not a suitable dressing for thesame reasons as were given by Olow and Hogeman.He considered that the dressing was superior to allother dressing methods used previously in cleanpaediatric surgery.Rob and Eastcott (1954), describing their find-

ings in the treatment of 200 clean operation woundsin man, which had been dressed with a plasticizedacrylic polymer resin, Nobecutane, stressed theneed for absolute haemostasis, otherwise theexudate lifted the film. In addition, the skin must be

90



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


absolutely dry to maintain the seal. If the woundis to be drained, a textile absorbent dressing mustbe applied to the area near the drain, while the restof the wound may be covered with the plastic film.Only one of their 200 cases became infected. Thespray-on dressing was found particularly valuablefor wounds of the face and scrotum, situations inwhich it is difficult to apply traditional dressings.They estimated that by using spray-on dressings thecost of dressing clean surgical wounds could bereduced by 20%.Ekengren (1954) studied the use of the spray-on

dressing, Nobecutane, in Korea. The polymer wasused as a pre-operative skin cover to provide asterile field. The wounds were closed with steelsutures and then sprayed with the resin. Approxi-mately 2,640 wounds were treated in this manner,including 438 United Nations Forces members whohad sustained war injuries. He found that becausethe steel sutures tended to project through the film,abdominal wounds had to be covered with a binderand limb wounds with an elastic dressing. Althoughthis was an uncontrolled clinical trial, the incidenceof infection seemed far less than with other types ofdressings. Infestation of the operation site withfly-larvae, which had been a problem previouslybecause of the hot, humid climate, did not occur.The dressing prevented a patient from probing hiswounds with dirty fingers and protected normal skinfrom the secretion of discharging wounds. Ekengrenalso made the point of the reduction in cost of thedressing of clean wounds. In hot climates and foremergency work the spray-on dressing seems to offera number of advantages. Unlike the adhesivedressing, the solution dressing is not subject todeterioration during storage, and there is a con-siderable saving in bulk and weight compared withthe traditional types of dressing. A disadvantagewith this type of dressing can be a faulty valve in theaerosol container, which allows evaporation of thepropellant.

Randall and Randall (1954) stated that the mostimportant indicator of the efficacy of a dressing isthe rate of epithelization. They pointed out that thehealing of a wound is influenced by many variables,such as the depth and extent of the wound, theamount of damaged tissue, contamination, activeinfection, and the condition of the patient. All theseare difficult to evaluate clinically, but by using labora-tory animals of an inbred strain, standard woundscan be made which reduce variables to a minimum.They believed that the skin of the mouse was a goodindicator, since partial-thickness wounds soonbecome converted into full-thickness wounds.Partial-thickness abrasion wounds, 2 x 3i cm.,were made on the backs of 16 g. mice with a razor,

and various dressings and medicaments were applied.They made only one wound on each animal, andno control dressing or medicament was used. Oneweek later the animal was sacrificed. They foundthat the use of a fabric dressing alone or with amedicament was preferable to the exposure treat-ment. One of the dressings they used was a polyvinylchloride co-polymer with other additives, known asAeroplast. They found that this dressing causedsevere collapse of the mice, an effect not reported inlarger animals, including man. They made the pointthat it is not possible to estimate by inspection theprogress of wound healing under a transparentdressing and that histological examination is alwaysnecessary. One of the disadvantages of the mouseis that the skin of certain rodents, notably the mouse,rat, and rabbit, has a regular cycle of physiologicalactivity, and in the mouse this cycle takes 30 days.It is thus exceedingly difficult to study the effects ofwound dressings unless a control is used on eachanimal and a very great number of animals isemployed.

Choy, reporting in 1954 on the treatment of 50patients with polyvinyl chloride and acetate co-polymer solution, 11 first- to third-degree burns,eight donor skin-graft sites, and 31 surgical wounds,claimed that there was no retardation in healingrate; that the film dressing was able to maintain thesterility of clean wounds; that the film could beeasily applied and removed; and that the dressingwas transparent.

However, the dressing should not be used oninfected wounds, otherwise pocketing of pus occurs.

Giles (1956) treated in a military hospital 48 casesof minor surgery and 60 cases of minor injurieswith the acrylic polymer solution Nobecutane. In12 patients haemorrhage occurred within the first12 to 24 hours and a firm dry dressing had to beapplied. In nine patients, who suffered minorinjuries and whose wounds were contaminated withdirt, clinical infection subsequently developed.

Wallgren (1957) studied the self-sterilizing andbacteriostatic properties, bacterial permeability,and the effect on the bacterial flora of intact skin offive film-forming polymer solutions in common useat that time: Aeroplast, a polyvinyl chloride andacetate co-polymer; Bonoplast, an acrylic polymer;Nobecutane, an acrylic polymer with tetramethylthiuramide disulphide; Newskin, a solution ofpyroxylin and camphor; and Portex plastic skin, amethyl ester of acrylic polymer.With the exception of Bonoplast, which is no

longer available, all the solutions were self-sterilizingafter 15 minutes, when 600 million organisms wereinoculated into 1 ml. of the solutions. The organismsused were Proteus vulgaris, Pseudomonas aeruginosa,

91



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


Escherichia coli, and four different strains ofMicrococcus pyogenes. The bacteriostatic propertiesof the films were investigated by half coveringblood-agar plates with the various solutions. Theplates were incubated for 24 hours at 37°C. All thefilms inhibited growth to a varying degree.

Using a suspension of 600 million organisms/ml.,2 ml. was spread on the surface of plastic films whichhad been made on blood agar plates according tothe makers' instructions. After removal of the filmat 24 hours, followed by re-incubation, growthwas obtained in the areas originally covered by thefilms, showing that pores of at least 0-8 to 1-0 ,u insize existed in the films. If complete impermeabilityto bacteria is required, films must be prepared byapplying a number of coats of the solutions in excessof the manufacturers' recommendations. Thethicker the film, the lower its porosity to watervapour and the less its flexibility.Wallgren found that applications of Aeroplast,

Bonoplast, Nobecutane, and Newskin to the normalskin of patients reduced the bacterial count after24 hours. His report also gives his clinical experiencewith plastic film dressings in the treatment of morethan 4,500 patients over three years. He claimed thatthe incidence of infection was below the 3 to 5%found in normal sterile surgery. He did not give anactual figure. He believed that the film dressings hada field of use in the treatment of clean surgicalwounds. If there is a possibility of infection withbacteria, traditional fabric dressings should beemployed, which will permit drainage.

Heite and Ludwig (1959), in a comprehensivereview of the work carried out with film-formingpolymer dressings, concluded that there was alimited use for the spray-on dressing in the treatmentof dry, clean operation wounds and that in thesecases the dressings could be left undisturbed for14 days or more. They also have a place in theprotection of normal skin from various wound andbody secretions and for some applications in derma-tology.The use of fabrics in conjunction with these

solutions has also been advocated, but the dis-advantage of rigidity and loss of transparency ofthe film seemed to offset any slight advantagesgained in other ways. The limited permeability towater vapour, the prevention of drainage of woundexudate, and the impossibility of using these filmsif complete haemostasis has not been achieved,limit their use. Providing, however, these contra-indications are borne in mind, the spray-on polymerdressing of the Nobecutane type is ideal for clean,surgical incisions and is probably the most suitabledressing to use. In areas subject to friction orweight-bearing, the film should be covered with a

gauze or cotton wool pad held in place by a con-forming bandage.From what has been said so far, it is apparent

that there is still a considerable difference of opinionregarding the methods of treating wounds and thechoice of materials. One thing, however, is certain:wound dressings are required to absorb woundexudate and to protect the wound.Our experience, when conducting clinical trials,

has shown that many of the beneficial therapeuticeffects of certain dressings are vitiated by thedamage caused to a healing wound when removingan adherent dressing. It is very difficult to study theadhesion of dressings by means of human clinicaltrials, since the wounds vary in extent, depth,situation, and bacterial flora. It is rarely possible tohave a control dressing on the same patient and tocarry out a biopsy of the wound to follow theprogress of healing. Adhesion of wound dressings isreally a problem of the adhesion of two surfaces by aglue, the exudate from the wound. One of thefunctions of a wound dressing is to be absorbent.and to achieve this a wettable and highly porousstructure is required, but it is just such a structurewhich provides the ideal surface for adhesion. Theother surface is a living, changing surface which addstissue fluids to the adhesive at a diminishing ratefor many hours. The composition of the adhesivewill vary according to the cellular elements present,and its viscosity may be affected by the proteolyticenzymes of the patient or by bacteria. At one timewe thought that the relative adherency or non-adherency of dressings could be determined in thelaboratory by drying human reconstituted serum incontact with various dressings, but only limitedinformation can be obtained by this method (Scalesand Winter, 1961). To try to confirm the laboratoryfindings, the materials tested have been used aswound dressings on the domestic pig. This animalwas chosen in preference to a small animal, such asthe rat, guinea-pig, or rabbit, because it has a broadexpanse of skin which can be effectively depilated;upwards of 12 large dressings can be put on at thesame time, and the dressings can be protected with acage. Changes of posture do not disturb the dress-ings as on a small animal. The skin is morphologic-ally similar to that of man, and there is evidencethat the mode of wound healing is also similar.

Hartwell (1955) stated that only in the domesticpig, which is an animal seldom used in woundresearch, did he find histological observations ofsub-epithelial wound healing by first intention,essentially similar to the histological observationshe had made in human wounds healing primarily.One inch square partial-thickness wounds 0-015 in.

deep were made on the backs of young pigs, approxi-

92



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


mately 50 lb. (22 6 kg.) in body weight, which hadbeen depilated three days previously. Steriledressings were carefully put over the wounds andheld in place by a ring of porous adhesive plasterwhich permitted the effective part of the dressingto be exposed to the atmosphere. The dressingswere protected by a cage held on the pig's back byelastic straps. Ten wounds were made on each pig;five were dressed with one of the materials undertest and five with cotton lint as controls. Thedressings were changed daily. Since each materialwas compared with cotton lint, all materials couldbe compared with one another. The results aresummarized in the Table.

TABLERATIO OF ADHESION OF VARIOUS DRESSINGS WHEN

COMPARED WITH COTTON LINT

A Cotton stockinet 0-6B Cotton lint 1-0C High- and low-twist rayon fabric 1l1D Woven rayon and cuprammonium strip film

dressing 1-3E Rayon lint 1-3F Tulle gras 1-3G Open-mesh continuous filament rayon dressing 1.5H Cellulose absorbent enclosed in perforated polyester

tube (0-15 mm. holes) 1-6I Saponified cellulose acetate fabric 1-6J Cellulose absorbent enclosed in perforated polyester

tube (0-65 mm. holes) 1-7K Impregnated acetate fabric 2-0L Triacetate fabric 4-1

It was found that cotton lint and stockinet are themost suitable of the conventional materials. Thefact that there were more adherent dressings withthe rayon lint than with the cotton lint (1-3: 1) maybe due to the fact that the rayon lint was producedfrom continuous-filament fabric. Histological studiesof wounds from which adherent dressings wereremoved showed that damage was done to thedelicate regenerating epidermis due to fibres becom-ing embedded in the exudate. A dressing can beremoved without damage to the wound only if thebond between the exudate and the epidermis isweakened by normal keratinization at the upperlayers of the epidermis and when the epidermisbecomes anchored by its downgrowths to the dermis.It was estimated that the completion of epithelizationin the partial-thickness wounds was delayed aboutthree days by the use of a cotton-lint dressing whichwas changed daily. The ratio of adhesion from theTable was determined from the number of adherentdressings. Since all the dressings were adherent tothe serous exudate, what factor is responsible forthe difference in the adhesion ratio? We believe thatit is the different constructions of the dressingsaffecting the rate at which the exudates dry whichis the decisive factor in adhesion. Construction alsoinfluences the volume uptake of the dressing and its

ability to maintain the correct environment for themaximum rate of epithelial proliferation.To study the effects of dressings further, it has

been found necessary to determine the healing rateof partial-thickness wounds, which are allowed toheal without a dressing, on the domestic pig. Therate of epithelial regeneration in a wound can onlybe studied by histological methods. The methodof estimating the rate of wound healing by plani-metry is inaccurate and unreliable, since a scab isformed which is not transparent and wound healingproceeds beneath it. Working with aseptic superficialwounds in the skin of the pig, Winter (1962) hasfound that by keeping the wounds moist under apolythene film, epithelization of the denuded surfaceis about twice as rapid as when the wounds areexposed to the air. The explanation for this seemsto be that the base of the wound becomes dehydratedby exposure and the regenerating epidermis has tomigrate along a plane in the dermis where the con-ditions are correct for the life of the cells. Theleucocytes or white cells are trapped in the de-hydrated layer and form with the exudate the normalscab which prevents the ingress of dirt and micro-organisms and protects the delicate cells fromdehydration. By covering the wound with a poly-thene film, dehydration is prevented and theepidermis is able to migrate over the cleanly-cutbase of the wound faster than it can pass throughthe dermis in the wound exposed to the air. Fortun-ately, the pig appears to have a high resistance toinfection compared with man, and therefore theneed for rapid concentration of the exudate andformation of the normal scab may not be so essential.

If all wound dressings of the absorbent type (andin the treatment of many types of wounds theyhave to be absorbent) adhere to wounds, thenobviously it is best to make use of this propertyand to use a fabric which is sufficiently weak not todisturb the exudate when the bulk of the dressingis removed. It is possible to reduce the tensilestrength of fine-weave acetate fabrics artificially to avalue which permits a dressing to be removed,leaving behind the part incorporated in the scab.

It seems that a dressing must be a compromise.Initially it should absorb wound exudate for in thisway bacteria are removed from the wound; it shouldpermit evaporation of fluid in order to allow con-centration of the exudate which in turn retardsbacterial growth; and the dressing must be of sucha construction that its removal does not disturbthe eschar beneath which the repair process istaking place. To achieve this the layer of thedressing in contact with the wound must have a lowtensile strength, probably in the region of 100 g./12-5 mm. width.

93



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/


ConclusionLooking back on the history of surgical dressings,

we have seen how progress has taken place in a

series of discrete steps, often with many barrenintervening years. The stimulus for each new advancehas been some new thought about wound treatment,some new knowledge about the wound-healingprocess itself, or the development of some new classof material in another field. In this century we havea whole host of new materials. We are able now

to define the problems associated with wounddressings more clearly than ever before. I believe itis essential to develop a standard method of assessingwound dressings. For this we must have an inter-nationally agreed standard dressing which can beused as a control dressing in all animal and humanwork. There are certain anatomical variations anddifferences in physiological activity of the skin ofthe mouse, rat, guinea-pig, and rabbit which makethe interpretation of experimental findings inrelation to man very difficult. The only suitableanimal with a skin morphologically similar to manis the domestic pig. A number of wounds can bemade on one animal which can be examined histo-logically at various times during healing. In an

assessment of wound dressings, three types ofwounds should be used: partial-thickness excisions;full-thickness excisions; and third-degree bums.The influence of a dressing on wound healing can bejudged only by histological examination of thewounds. While this method of assessing a wounddressing might appear costly and time-consuming, itwould allow an international comparison of wounddressings which would be of benefit to the patient,to industry, and, in many countries, to the nationaleconomy.

In an effort to help and stimulate research, the Inter-national Rayon and Synthetic Fibres Committee hassponsored a survey of literature concerned with woundhealing and dressing. I have been most fortunate in

having access to the excellent abstracts that Dr. L. J. M.Laurent has made.

REFERENCES

Arey, L. B. (1936). Physiol. Rev., 16, 327.Bailey, H., and Bishop, W. J. (1946). Notable Names in Medicine and

Surgery, 2nd ed., p. 93. Lewis, London.Baron, H. (1956a). Arzneimittel-Forsch., 6, 277.

(1956b). Berufsdermatosen, 4, 29.(1957). Reyon Zellwolle und andere Chemiefasern. Informations-stelle, Frankfurt.

Bishop, W. J. (1959). A History of Surgical Dressings. Robinsonand Sons, Chesterfield.

Blaine, G. (1947). Ann. Surg., 125, 102.Blakiston's Illustrated Pocket Medical Dictionary (1952). 1st ed.,

ed. N. L. Hoerr and A. Osol. Blakiston, New York.Bloom, H. (1945). Lancet, 2, 559.Bull, J. P., Squire, J. R., and Topley, E. (1948). ibid., 2, 213.Burtenshaw, J. M. L. (1945). Brit. med. Bull., 3, 161.Choy, D. S. J. (1954). A.M.A. Arch. Surg., 68, 33.Ekengren, A. (1954). Nord. Med., 51, 854.Frantz, V. K. (1948). Ann. Surg., 127, 1165.Gamgee, S. (1880a). Lancet, 1, 127.

(1880b). ibid., 1, 308.Gelinsky, E. (1954). Zbl. Chir., 79, 1354.

(1957). Bruns' Beitr. klin. Chir., 195, 160.Giles, K. W. (1956). Brit. med. J., 1, 727.Gillman, T., and Hathorn, M. (1957). Transplant. Bull., 4, 65.

and Penn, J. (1956). Plast. reconstr. Surg., 18, 260.Gordon, B. L. (1959). Medieval and Renaissance Medicine. Philoso-

phical Library, New York; Peter Owen, London.Gray, G. H., and Jones, H. W. (1956). Plast. reconstr. Surg., 17, 471.Hartwell, S. W. (1955). The Mechanisms ofHealing in Human Wounds.

Thomas, Springfield, Illinois.Heifetz, C. J., Lawrence, M. S., and Richards, F. 0. (1952). A.M.A.

Arch. Surg., 65, 746.Richards, F. O., and Lawrence, M. S. (1953). ibid., 67, 661.

Heite, H. J., and Ludwig, M. (1959). Munch. med. Wschr., 101, 415.Hoffmeister, H. (1959). Med. Klin., 54, 1243.Korlof, B. (1954). Acta chir. scand., 107, 244.Lister, J. (1867). Lancet, 2, 353.Lowbury, E. J. L., and Fox, J. (1953). J. Hyg. (Lond.), 51, 203.Marshak, A. (1945). Proc. Soc. exp. Biol. (N. Y.), 58, 63.Olow, B., and Hogeman, K. E. (1953). Transactions of the Meeting

of the Northern Surgical Association in Gothenburg.Owens, N. (1946). Surgery, 19, 482.P.A.T.R.A. (1948). Packaging Research Report No. 2. Printing,

Packaging, and Allied Trades Research Association.Pharmaceutical Society of Great Britain (1959). British Pharma-

ceutical Codex, 7th ed. Pharmaceutical Press, London.Randall, P., and Randall, R. J. (1954). Plast. reconstr. Surg., 14, 105-Rice, R. H., and Vogt, P. R. (1955). Northw. Med. (Seattle), 54, 162,Rob, C. G., and Eastcott, H. H. G. (1954). Brit. med. J., 2, 17.Savage, R. M., Bryce, D. M., and Elliott, J. R. (1952). J. Pharnm.

Pharmacol., 4, 944.Scales, J. T. (1954). Trans. Ass. industr. med. Offrs, 4, 69.

Towers, A. G., and Goodman, N. (1956). Brit. med. J., 2, 962.and Winter, G. D. (1961). In Wound Healing. Proceedings of a

Symposium 12/13 November 1959, London, ed. D. Slome,p. 54. Pergamon Press, Oxford.

Schilling, R. S. F., Roberts, M., and Goodman, N. (1950). Lancet, 1, 293.Wallgren, G. R. (1954). Ann. Chir. Gynaec. Fenn., 43, 279.

(1957). Acta chir. scand., 112, 161.Williams, R. E. O., and Miles, A. A. (1945). J. Path. Bact., 57, 27.Winsor, T., and Burch, G. E. (1944). Arch. intern. Med., 74, 428.Winter, G. D. (1962). Nature (Lond.), 193, 293.

94



.bmj.com

/B


.20.2.82 on 1 April 1963. D

ownloaded from

http://oem.bmj.com/

Documents

WOUND HEALING ANDTHEDRESSING* · wound as soon as possible, one should dry the wound... for whatis soonest dried up. . . thereby most readily separates from the rest of the tissue