A wound is damage to the skin and sometimes to deeper underlying tissue and even organs as a result of mechanical, thermal or chemical injury.
The wounds caused by mechanical injury include: abrasions, cuts, cracks, stab wounds, bite and surgical wounds.
The wounds caused by thermal or chemical injury include: all kinds of thermal, chemical, electrical or radiation burns.
There are certain types of wounds – chronic (non-healing) wounds, which are caused by other processes – disease processes. Chronic wounds include: pressure ulcers (trophic ulcers), venous ulcers, neuropathic ulcers and ulcers caused by infections and as a result of radiotherapy or neoplastic processes.
Types of wound healing
1. Slowly healing wounds – healing by granulation
- significant loss of tissue
- the wound cannot be closed by using physical methods
- long healing time
- the treatment is based on the processes of tissue reconstruction – the defect fills in with granulation tissue, on which epidermis appears and forms a scar
2. Acute wounds – temporary healing by first intention
- surgical or fresh traumatic wounds
- minimum loss of tissue
- edges are joined by seams or using a plaster
There is no one universal dressing that can be used in each case.
Dressings have different functions: cleansing, absorbent and protective, they often complement each other and none of them alone can meet all the needs of the wound passing through the healing stages:
- inflammation phase (exudate)
- granulation and epithelisation phase (growth)
- maturation phase (reconstruction)
Inflammation phase (exudate)
This phase is the body’s response to an injury. Due to circulatory disorders, enlargement and increased permeability of capillaries oedema occurs, accompanied by exudate.
Functions of the dressing in the inflammation phase:
- stemming the bleeding
- facilitating natural debridement
- absorbing excess exudate
- preventing re-infection
Granulation and epithelising phase (growth)
Granulation – the change from the inflammatory phase into the proliferative phase, which is controlled by macrophages and other cells. Macrophages stimulate fibroblast growth.
Narrowing of the wound – many fibroblasts is transformed into myofibroblasts. The network of connected myofibroblasts pulls the edges of the wound together (0.6-0.7 mm/day).
Epithelisation - new epidermis, which is needed for the complete closure of the wound. Epidermal cells migrating from the edges of the wound cover the granulation tissue and create new skin.
Functions of the dressing in the growth phase:
- maintaining moist environment
- absorbing excess exudate
- protecting against mechanical injury
- preventing re-infection
- maintain a moist environment
- protecting delicate epidermis during dressing changes
Maturation – slow reorganisation of microscopic structure of scar tissue; the remodelling results in improving the strength of the scar, its reduction and smoothing.
This stage can last for months or even years.
In the treatment of abnormal scarring are the following items are used:
- topical silicone dressings
- compression bandages or special compression garments
- surgery, corticosteroid therapy, laser and cryosurgery
Functions of the dressing in the maturation phase:
- smoothing the scar
- whitening the scar
- reducing the scar
What is wound exudate?
Wound exudate is a particular fluid called in the past „nature balm” appears in the first stage of wound healing, immediately after an injury.
The exudate contains a variety of ingredients including nutrients for actively metabolising cells:
- very few red blood cells
- up to 6 times more white blood cells than in the blood
- less glucose, but the same amount of minerals as the blood
- proteins – among which there are enzymes important for the wound healing processes; the released enzymes cleanse the wound and remove damaged tissues
In a normally healing wound the amount of exudate decreases with time. In a wound, in which the healing process is disturbed, the amount of exudate is not reduced in time and its management can be a big challenge for dressings.
NOTE: to maintain the best possible conditions for wound healing the optimal amount of wound exudate is needed, namely a so-called moist wound healing environment.
Too much exudate and its absence can slow down the healing process. Therefore, it is important to choose an appropriate dressing to the amount of wound exudate. In wounds dry without exudate the dressing should moisten, and in wounds with too much exudate preferably the dressing should absorb its excess.
NOTE: The change in colour, odour and exudate density may indicate a change in the wound or the appearance of inflammation / infection – it is a signal that the wound should be examined and assessed by a specialist.
Dressing type vs. indication for its use in wounds with various exudate amount
|Dressing type||Level of exudate|
|challenge for the dressing||hydrate the wound||maintain a moist environment||absorb the excess of exudate||absorb the excess of exudate|
Wound treatment models
The traditional wound healing model
Through the centuries chronic wounds were treated using a variety of materials that were to dry the wound.
The traditional wound treatment system based on the use of absorbent dressings made of gauze which:
- ensured the absorption of excess exudate
- failed to protect the wound against drying out and cooling down, which slowed down the rate of healing
- did not constitute adequate protection against external factors, which could lead to frequent wound infections
- adhered to the wound, which damaged the new tissue and caused pain to the patient during dressing changes
- with limited absorptive capacity compelled to frequent dressing change
Dry wound healing is still the most desirable but for acute wounds healing by first intention.
The modern wound healing model
Since the publication of research by George Winter, it became clear that wounds heal much more quickly if the healing process is carried out in humid conditions in which the optimal amount of exudate is maintained on the surface of the wound. In view of the conditions under which the treatment process takes place, the concept was called A MOIST WOUND HEALING.
According to this concept, the treatment deals with closing the wound with a special dressing which:
- maintains the required level of moisture on the wound surface to create an optimal healing environment
- initiates autolytic cleansing, which leads to faster debridement and to start the healing process
- thermally isolates the wound which keeps the temperature at a constant level and accelerates the healing process
- provides long-term absorption of excess exudate, reducing the number of dressing changes
- does not adhere to the wound thanks to which dressing change is safe for young tissues and painless for the patient
- is water-resistant and protects the wound against external environment, which minimises the risk of infection
Features of a perfect dressing
Moist wound healing is most appropriate for hard-to-heal wounds but it can be also used for the treatment of usual cuts, abrasions or scratches.