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.

Many burned people die, their body couldn’t 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

Functions of Skin?Functions of Skin? Skin is the largest organ in the

human body Helps preserve fluid balance Controls body temperature Helps prevent and fight diseases

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

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.

Superficial

Deep (blood vessels, nerves, muscle, tendons, ligaments, bones)

Open Wound Superficial or deep break in skin

(abrasion, puncture, laceration)

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

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

Inflammatory Response Serum and RBC’s 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

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

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

1. Vascular Response

2. Blood coagulation

3. Inflammation4. Formation of new

tissue5. Epithelialisation6. Contraction &

Remodeling

Inflammatory Bleeding/clotting Migration of WBCs Cell swelling

Reparative Laying down of collagen + migration of epith. cells New capillary loops Proliferation of fibroblastsstrands of collagen

Consolodative reorientation +contraction of collagen collagen synthesisdegradation vascularity

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

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

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

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

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

Gauze Dressings Transparent Films Foams Hydrocolloids Alginates Composites

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.

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.

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, won’t 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.

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.

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.

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.

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).

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.

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.

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.

• 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.

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.

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

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

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

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.

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

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.

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.

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.

"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)

b) 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.

d) Peeling force lifts graft away from woundbed.

f) Very low moisture flux causes fluid accumulation at graft-woundbed interface and peeling.

Types of Skin ReplacementsTypes 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.

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.

BenefitsBenefits

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

Biodegradable skin Doesn’t 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

BiobraneCan be easily peeled off; good for donor sites and superficial partial-thickness burns within 6 hrs; shortens time in hospital; low cost

Temporary coverage

TranscyteReadily 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

ApligrafImmediate 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

DermagraftReadily available; living dermal structure; used for chronic lesions, foot ulcers.

Temporary coverage; only 1 main application

ProductAdvantagesDisadvantages

Advantages and Disadvantages of Temporary Skin Substitutes

IntegraImmediate permanent wound coverage; allows ultra-thin split-thickness skin autografts; most widely accepted for burn patients; allows migration of patient’s 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.

AllodermImmediate 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

EpicelCovers 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;

LaserskinDelivers keratinocytes to the wound in an upside-down manner

Expensive

ProductAdvantagesDisadvantages

Advantages and Disadvantages of Permanent Skin Substitutes

Types of Skin Types of Skin Replacements 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

How does it work?How does it work?

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

Drape a sheet of Integra ® over the wounded area for 2 to 4 weeks.

Allows the victim’s 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 victim’s own epithelial cells.

Over time, a normal epidermis (except for the absence of hair follicles) is reconstructed from these cells.

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