Wound Dressing

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Wound Dressing Artificial Skin
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Introduction

• Our skin is a major organ of the body that acts
  as a barrier to pathogens and trauma.
• Skin defects caused by burns, venous and diabetic
  ulcers, or acute injury occasionally induce
  life-threatening situations.

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Introduction

• Many burned people die, their body couldnt
  produce new skin
• Skin is largest organs in the body
• Skin is important to protect body from infection
  and harmful bacteria
• Skin keep vital fluid in

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Functions of Skin?

• Skin is the largest organ in the human body
• Helps preserve fluid balance
• Controls body temperature
• Helps prevent and fight diseases

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Wounds

• What are wounds ?
• Break in skin or mucous membranes
• Any breach in the surface of the body or any
  tissue disruption produced by the application of
  energy
• Usually physical injury
• Abrasion injury
• Contusion, crush injury
• Incision, laceration

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The Anatomy of Human Skin

• Epidermis (5 layers)
• Keratinocytes provide protective properties.
• Melanocytes provide pigmentation.
• Langerhans cells help immune system.
• Merkel cells provide sensory receptors.
• Dermis (2 layers)
• Collagen, glycoaminoglycans, elastine, ect.
• Fibroblasts are principal cellular constituent.
• Vascular structures, nerves, skin appendages.
• Hypodermis (fatty layer)
• Adipose tissue plus connective tissue.
• Anchors skin to underlying tissues.
• Shook absorber and insulator.

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Wound Classification

• Superficial
• Deep (blood vessels, nerves, muscle, tendons,
  ligaments, bones)
• Open Wound
• Superficial or deep break in skin (abrasion,
  puncture, laceration)

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Wound Classification

• Closed blunt force twisting, turning,
  straining, bone fracture, visceral organ tear
• Acute trauma sharp object or blow
• Surgical incision, gun shot, venipuncture
• Chronic pressure ulcers
• Causality
• Intentional surgical incision
• Unintentional traumatic
• Knife
• Burn

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Wound Healing

• Primary Intention
• skin edges are approximated (closed) as in a
  surgical wound
• Inflammation subsides within 24 hours (redness,
  warmth, edema)
• Resurfaces within 4 to 7 days
• Secondary Intention tissue loss
• Burn, pressure ulcer, severe laceration
• Wound left open
• Scar tissue forms

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Wound Healing Phases

• Inflammatory Response
• Serum and RBCs form fibrin network
• Increases blood flow with scab forming in 3 to 5
  days
• Proliferative Phase 3-24 days
• Granulation tissue fills wound
• Resurfacing by epithelialization
• Remodeling more than 1 year
• collagen scar reorganizes and increases in
  strength
• Fewer melanocytes (pigment), lighter color

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Some Factors Influencing Wound Healing

• Age
• Nutrition protein and Vitamin C intake
• Obesity decreased blood flow and increased risk
  for infection
• Tissue contamination pathogens compete with
  cells for oxygen and nutrition
• Hemorrhage
• Infection purulent discharge
• Dehiscence skin and tissue separate
• Evisceration protrusion of visceral organs
• Fistula abnormal passage through two organs or
  to outside of body

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Wound Healing

• As wound heals
• Fluid and cells drain from damaged tissue
• Exudate may be
• Clear
• Bloody
• Pus-containing
• Proper wound healing
• Cleanliness and care of lesion
• Proper circulation
• Good general health and nutrition

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Wound Healing

1. Vascular Response
2. Blood coagulation
3. Inflammation
4. Formation of new tissue
5. Epithelialisation
6. Contraction Remodeling

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Phases of healing

• Inflammatory
• Bleeding/clotting
• Migration of WBCs
• Cell swelling
• Reparative
• Laying down of collagen migration of epith.
  cells
• New capillary loops
• Proliferation of fibroblasts?strands of collagen
• Consolodative
• reorientation contraction of collagen
• collagen synthesis?degradation
• ? vascularity

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Burn Injuries

• Statistics
• Annually, there are approximately 1.25 million
  people in the US who sustain burn injuries
• Of these, 5,500 do not survive and 51,000 require
  hospitalization
• Persons whose burn injuries require
  hospitalization have about a 50 chance of
  sustaining temporary or permanent disability
• The most common part of the body involved in burn
  injury is an upper extremity, followed by the
  head and neck

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Burn Classification - Cause

• The primary cause of burn injury is exposure to
  temperature extremes
• Heat injuries are more frequent than cold
  injuries
• Cold injuries almost exclusively result from
  frostbite
• Electrical and chemical injuries constitute 5-10
  of burn injuries and are largely the result of
  occupational accidents

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Effects

• Burn injury causes destruction of tissue, usually
  the skin, from exposure to thermal extremes
  (either hot or cold), electricity, chemicals,
  and/or radiation
• The mucosa of the upper GI system (mouth,
  esophagus, stomach) can be burned with ingestion
  of chemicals
• The respiratory system can be damaged if hot
  gases, smoke, or toxic chemical fumes are inhaled
• Fat, muscle, bone, and peripheral nerves can be
  affected in electrical injuries or prolonged
  thermal or chemical exposure
• Skin damage can result in altered ability to
  sense pain, touch, and temperature

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Burn Classification - Depth

• Old terminology
• 1st degree only the epidermis
• 2nd degree epidermis and dermis, excluding all
  the dermal appendages
• 3rd degree epidermis and all of the dermis
• 4th degree epidermis, dermis, and subcutaneous
  tissues (fat, muscle, bone, and peripheral nerves)

• New terminology
• Superficial only the epidermis
• Superficial partial thickness epidermis and
  dermis, excluding all the dermal appendages
• Deep partial thickness epidermis and most of
  the dermis
• Full thickness epidermis and all of the dermis

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PRIMARY WOUND DRESSINGSPrimary wound dressing
is applied directlyto wounds to protect from
contamination,absorb exudates and facilitate
healing.They are in the form ofSelf
adhesives and do not need a secondary
dressing.An interface layer between the wound
andthe secondary dressing.
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CHARACTERSTICS OF IDEALWOUND DRESSING

• Maintain humidity
• Remove excess exudates
• Allow gaseous exchange
• Provide thermal insulation
• Impermeable to bacteria
• Allow removal without causing trauma
• Non toxic and non allergenic
• Cost effective
• Availability

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Wound Dressing Selection Types and Usage

• Gauze Dressings
• Transparent Films
• Foams
• Hydrocolloids
• Alginates
• Composites

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Gauze dressings

• Woven or non-woven materials
• Wide variety of shapes and sizes.
• Use on infected wounds, wounds which require
  packing, wounds that are draining, wounds
  requiring very frequent dressing changes.
• Pros readily available cheaper than other
  dressing types can be used on virtually any type
  of wound.
• Cons must be changed frequently, which may add
  to overall cost may adhere to the wound bed
  must often be combined with another dressing
  type often not effective for moist wound
  healing.

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Transparent film dressings

• Allow oxygen to penetrate through the dressing to
  the wound, while simultaneously allowing moisture
  vapor to be released.
• Composed of a polyurethane material.
• Use on partial-thickness wounds, donor sites,
  minor burns, stage I and II pressure ulcers.
• Pros conforms to the wound well, can stay in
  place for up to one week aids in autolytic
  debridement prevents friction against the wound
  bed does not need to be removed to visualize the
  wound keeps the wound bed dry and prevents
  bacterial contamination of the wound.
• Cons may stick to some wounds, not suitable for
  heavily draining wounds, may promote periwound
  maceration due to its occlusive nature.

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Foams

• Less apt to stick to delicate wound beds, are
  non-occlusive and are composed of a film coated
  gel or a polyurethane material which is
  hydrophilic in nature.
• Use on pressure ulcers, minor burns, skin
  grafts, diabetic ulcers, donor sites, venous
  ulcers.
• Pros comfortable, wont adhere to the wound bed,
  and highly absorbent allow for less frequent
  dressing changes, depending on the amount of
  wound exudate come in many shapes and sizes.
• Cons may require a secondary dressing to hold
  the foam in place if not changed often enough
  may promote periwound maceration cannot be used
  on wounds with eschar or wounds that are not
  draining.

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POLYUNETHANE FOAM DRESSING

• Varying types and with different performance
  features and indications.
• Available in both non adhesive and adhesive.
• Allows absorption of exudates.
• Uses Traumatic wounds, Leg ulcers, Minor Burns,
• Donor sites.
• Examples
• Lyofoam allows passage of fluid
• Allevyn has low-adhering wound contact with
  moderate exudates
• Tielle allows vapour escape with low exudates.

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POLYUNETHANE FOAM DRESSING Lyofoam
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Hydrocolloid dressings

• Very absorbent and contain colloidal particles
  such as methylcellulose, gelatin or pectin that
  swell into a gel-like mass when they come in
  contact with exudate.
• Strong adhesive backing.
• Use on burns, pressure ulcers, venous ulcers.
• Pros encourage autolytic debridement provide
  insulation to the wound bed waterproof and
  impermeable to bacteria, urine or stool provide
  moderate absorption of exudate.
• Cons leave a residue present in the wound bed
  which may be mistaken for infection may roll
  over certain body areas that are prone to
  friction cannot be used in the presence of
  infection.

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HYDRO GEL DRESSINGS

• Consist of insoluble polymers with hydrophilic
  sites, which interact with aqueous solutions,
  absorb and retain water.
• Key Features
• Removes slough and necrotic tissue by rehydrating
  dead tissue and enabling autolytic debridement.
• Carries metronidazol to treat fungal and other
  malodorous wounds.
• Uses Sinuses, Infected wounds, Sloughs and
  necrotic wounds.
• Examples
• Intrasite gel, Neugel, Granugel.

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Alginates

• Contain salts derived from certain species of
  brown seaweed.
• Woven or nonwoven
• Form a hydrophilic gel when they come in contact
  with exudate from the wound.
• Use on venous ulcers, wounds with tunneling,
  wounds with heavy exudate.
• Pros highly absorbent may be used on wounds
  that have infection present are non-adherent
  encourage autolytic debridement.
• Cons always require a secondary dressing, may
  cause desiccation of the wound bed, as well as
  drying exposed tendon, capsule or bone (should
  not be used in these cases).

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ALGINATE DRESSINGS

• Consist, principally of calcium salts of alginic
  acid, a polysaccharide derived from seaweed.
• Key Features
• The calcium alginate in contact with the wound
  exudates forms a gel on the wound surface that is
  believed to facilitate healing.
• The chemical and physical properties differ in
  the varieties of alginate on available.
• Plain or impregnated with silver.
• Examples
• Saesorb, Kaltogel, Kaltostat, Sorbsan, Tegagen,
  Acquacel.

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Composites

• May be used as the primary dressing or as a
  secondary dressing.
• Made from any combination of dressing types, but
  are merely a combination of a moisture retentive
  dressing and a gauze dressing.
• Use on a wide variety of wounds, depending on
  the dressing.
• Pros widely available simple for clinicians to
  use.
• Cons may be more expensive and difficult to
  store less choice/flexibility in indications for
  use.

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The best material for wound closure is the
patients own skin however autografting has
several disadvantages

1. The donor site is a new wound.
2. Scarring and pigmentation changes occur.
3. Dermis is not replaced.
4. Donor site is a potential site for infection.
5. Donor site is not unlimited.
6. Extensive burns makes it impossible.

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Xenografts

• Xenografts, particularly porcine skin grafts,
  are
• commercially available and are an effective means
  of short-term wound closure .
• A Xenograft is normally removed on the third
  or
• fourth day of use before extensive adhesion onto
  the wound bed sets in, thereby necessitating its
  traumatic excision prior to drying and sloughing
  off.

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Cadaver Skin Allograft as a Temporary Skin
Substitute

• The annual national requirement for cadaver skin
  is estimated to be only 3000 m2.
• Yet only 14 to 19 of human skin needed is being
  recovered.

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Synthetic Skin

• Traditional solution replacing the skin with
  another human or animal skin
• Some of the body rejects others skin
• So, alternative solution needed
• Synthetic Skin is invented by Burke and Yannas

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Definition Synthetic Skin

• Is laboratory production for substitution of
  human skin (tissue Engineering)
• Tissue Engineering is Knowledge of building or
  repairing human organ
• Cells brought from lab or patients blood used to
  initiate the process

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Artifical Skin

• Graft should be flexible enough to conform to
  wound bed and move with body
• Should not be so fluid-permeable as to allow the
  underlying tissue to become dehydrated but should
  not retain so much moisture that edema (fluid
  accumulation) develops under the graft

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Eight Functions of Human Skin

1. Protect underlying tissues from injury
   mechanical, heat, cold, biological.
2. Prevent excess water loss.
3. Act as a temperature regulator.
4. Serve as a reservoir for food and water adipose
   tissue
5. Assist in the process of excretion H20, Salt,
   Urea, Lactic Acid.
6. Serve as a sense organ for cutaneous senses
   pain, heat, cold, pressure, touch.
7. Prevent entrance of foreign bodies
   microorganisms.
8. Serve as a seat of origin for Vitamin D.

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Artificial Skin - Possibilities

• Polymeric or collagen-based membrane
• Some are too brittle and toxic for use in burn
  victims
• Flexibility, moisture flux rate, and porosity can
  be controlled
• Fabrics and sponges designed to promote tissue
  ingrowth
• Have not been successful
• Immersion of patients in fluid bath or silicone
  fluid to prevent early fluid loss, minimize
  breakdown of remaining skin, and reduce pain
• Culturing cells in vitro and using these to
  create a living skin graft
• Does not require removal of significant portions
  of skin

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How Artificial Skin is Made

• Skin is usually donated by other donors.
• Fibroblasts are removed from the donated skin and
  are frozen until they are needed.
• The fibroblasts are placed on a polymeric mesh
  scaffolding, gather oxygen, and grow new cells.
• The cells are then transferred to a culture
  system.

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Artificial Skin cont.

• After 4 weeks the polymer mesh dissolves and
  leaves behind a new layer of dermal skin.
• When the growth cycle is completed, they add more
  nutrients.
• Keratinocytes are added to the collagen and are
  exposed to air to form epidermal layers.
• The skin is now completed and is stored in
  sterile contains until ready to use.

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Synthetic Polymers (Yannas, 1980)

• A high incidence of infection
• Low capacity for inducing vascularisation and
  epithelialisation
• However, useful insights into the requirements
  for a satisfactory skin replacement have been
  discovered through the use of synthetic polymers.

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General Design Properties

• "The dermal replacement should provide both the
  information necessary to control the inflammatory
  and contractile processes and also the
  information necessary to evoke ordered recreation
  of autologous tissue in the form of a neodermis"
  (Schulz, 2000).
• "The initial replacement material should provide
  immediate physiologic wound closure and be
  eliminated once it has provided sufficient
  information for reconstitution of neodermis"
  (Schulz).
• It should protect the wound by providing a
  barrier to the outside (Beele, 2002)
• It should control water evaporation and protein
  and electrolyte loss (Beele)
• It should limit excessive heat loss (Beele)
• It should decrease pain and allow early
  mobilization (Beele)
• It should provide an environment for accelerated
  wound healing (Beele)
• The risk of infection must be taken into account
  (Beele)

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Specific Physiochemical and Mechanical Problems
to Overcome (Yannas, 1985).

• Flexural rigidity of graft is excessive graft
  does not deform sufficiently under its own weight
  to make contact with depressions in woundbed
  surface, thus air pockets form.
• Peeling force lifts graft away from woundbed.
• f) Very low moisture flux causes fluid
  accumulation at graft-woundbed interface and
  peeling.

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Types of Skin Replacements

• Epicel skin replacement technology
• Introduced by Genzyme Biosurgery in 1987.
• Isolation of individual cells from a
  postage-stamp-sized biopsy of skin.
• Grow the cells for about 2 to 3 weeks and allow
  them to form individual sheets of tissue.
• Surgeons transplant these sheets of tissue to the
  burnt area where these sheets fuse over time with
  the burnt area.

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How Artificial Skin is Used

• Artificial skin is already being used for burn
  victims and soon will be available for other skin
  disorders.
• The skin is not used for a permanent replacement,
  but to temporary cover the skin until your skin
  can grow back naturally.

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Benefits

• Protect skin from infection
• Keep in moisture to prevent dehydration
• Encourage healing through construction of new
  tissue by infiltration of epidermal cells and
  fibroblasts
• Allow for less severe scarring
• More readily available

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Improvements

• Biodegradable skin
• Doesnt need to be removed
• Slowly releasing antibiotic
• Prevents infection
• Re freeze dried artificial skin
• Easier storage and reconstitution
• Addition of epithelial growth factor and basic
  fibroblast growth factor
• Increased regeneration of tissue

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Advantages and Disadvantages of Temporary Skin
Substitutes
Product Advantages Disadvantages
Biobrane Can be easily peeled off good for donor sites and superficial partial-thickness burns within 6 hrs shortens time in hospital low cost Temporary coverage
Transcyte Readily available easier to remove than allograft good for partial-thickness burns stimulates epithelialisation less scarring improves healing rate. Temporary coverage cost 16 times more than Biobrane
Apligraf Immediate availability 1 step procedure easy to handle primary role is treatment of chronic ulcers hastens healing in deep and chronic wounds improves cosmetic and functional outcomes Temporary coverage limited viability most expensive
Dermagraft Readily available living dermal structure used for chronic lesions, foot ulcers. Temporary coverage only 1 main application
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Advantages and Disadvantages of Permanent Skin
Substitutes
Product Advantages Disadvantages
Integra Immediate permanent wound coverage allows ultra-thin split-thickness skin autografts most widely accepted for burn patients allows migration of patients own endothelial cells and fibroblasts studies over 10 years now cosmetically better than using just autograft greater elasticity avoids risk of infection Complete wound excision 2 step procedure susceptible to infection relatively expensive compared to cadaveric allografts learning curve is steep.
Alloderm Immediate permanent wound coverage good for being a template for dermal regeneration good take rates reduces scarring allows 1 step grafting of an ultra thin split skin graft Allograft supply little barrier function no virus screening 2 step procedure most expensive
Epicel Covers large areas permanent immediate permanent wound coverage minimal risk of disease transmission 3 5 wks to produce 1.8 m2 from 2 cm2 fragile expensive because of quality control spontaneous blistering susceptible to infection and contractures
Laserskin Delivers keratinocytes to the wound in an upside-down manner Expensive
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Types of Skin Replacements

• Integra Dermal Regeneration Template
• Semi -synthetic approach to skin regeneration
• Researchers develop a bi-layer membrane system
  called the Dermal Regeneration Template
• The first and only FDA approved tissue engineered
  product for burn and reconstructive surgery
• Dermal replacement layer is constructed of a
  porous, biodegradable matrix of cross-linked
  bovine tendon collagen and the glycos-aminoglycan
  chondroitin 6-sulfate.
• Allows a the wound to establish a new tissue base

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How does it work?

• Drape a sheet of Integra over the wounded area
  for 2 to 4 weeks.
• Allows the victims cells to grow a new dermis on
  top of matrix of the Integra .
• Remove the top layer of the Integra and applies
  a very thin sheet of the victims own epithelial
  cells.
• Over time, a normal epidermis (except for the
  absence of hair follicles) is reconstructed from
  these cells.

• Skin replacement. Using a bilayer membrane
  system, scientists at Integra LifeSciences help
  repair skin lesions and burns.

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Synthetic Skin Manufacturing process
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Synthetic Skin Manufacturing process
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Synthetic Skin Manufacturing process
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Synthetic Skin Manufacturing process

• Using only labor manual process only 50,000 skins
  produces in a year
• So Automated processes needed
• Machine that refresh nutrient liquid every day
  (increase the time of growth)
• Temperature monitor, steady environment increase
  the growth