1, the concept of wound: is the normal skin (tissue) in the external injury-causing factors such as surgery, external force, heat, electricity, chemical substances, low temperature and the body’s intrinsic factors such as local blood supply disorders caused by the action of damage. It is often accompanied by the destruction of skin integrity and the loss of a certain amount of normal tissue, and at the same time, the normal function of the skin is impaired. Also called trauma.
2.Wound classification.
According to the healing time of making wounds, it is divided into acute wounds and chronic wounds. There is no uniform standard about the definition of acute/chronic trauma. It is generally considered that acute trauma refers to all wounds within the first 2 weeks from the formation of trauma. Subsequently, the healing process is partially or completely stopped due to some adverse influences such as infection, foreign body, etc., which causes the wound to heal for more than 2 weeks, at which point the wound is called a chronic wound. It can be seen that all chronic wounds are developed from acute wounds. Common acute wounds are: Surgical incision Skin abrasion Burns
(1) Skin donor area (Donor site)
(2) Common chronic wounds are
(3) Decubitus ulcers (Pressure sores)
(4) Lower extremity vascular (arterial/venous)
(5) Ulcers (Leg Ulcer)
(6) Diabetic foot ulcers (Diabetic foot)
(7) Other hard-to-heal wounds (Hard-to-healing)
Once a wound is formed, the body responds quickly to initiate the healing process to repair it. However, different wounds have different characteristics and their healing process varies, which leads to different ways of wound healing.
Acute wounds
(1) refers to a healing process that conforms to the classical time of wound repair
(2) Wounds that can heal spontaneously
(3) Can heal quickly and normally
(4) Healing starts from the hemostatic stage
Mainly surgical incisions, post-traumatic clean wounds and partially contaminated wounds
Chronic wounds
(1) Wounds with extended healing time
(2) Wounds that require external force to heal
(3) Not healing properly
(4) Lack of hemostatic phase due to lack of blood supply
(5) Contaminated or polluted wounds, formed after the occurrence of infection
According to the depth of wound damage, wounds can be divided into four types.
(1) Stage I —— skin is intact, blood vessels are damaged, erythema that does not turn white under finger pressure
(2) Stage II —— superficial injury. The injury is limited to the involvement of the epidermal layer of the skin and does not exceed the dermis, manifesting as epidermal peeling, or blistering. When the wound is small, its healing is achieved through the division, proliferation and differentiation of basal cells that migrate upward to achieve wound healing; if the wound is large, the healing is initiated by the division and proliferation of surviving basal cells at the perimeter of the wound to start the healing process. Usually, the original structure and function can be fully restored 2-4 days after the injury. Therefore, the healing of these wounds is correspondingly simple.
(3) Stage III —— Dermal injury. The injury is deeper, reaching the dermis and even the subcutaneous tissue.
(4) Stage IV —— full-layer injury. The injury is deep to the fascia, tendon or muscle layer, often accompanied by rupture of blood vessels, nerves and even bones.
According to the clinical manifestations of the wound, the wound can be divided into: red wounds, yellow wounds, black wounds 1988 by the American Journal of Nursing from Europe introduced the trauma RYB classification method RYB method will be stage II or delayed healing open wounds (including acute and chronic wounds) into red, yellow, black and mixed types. Red wounds, which may be in the inflammatory, proliferative or mature stages of the wound healing process; yellow wounds, which are infected wounds or contain fibrinous scabs with no readiness to heal; and black wounds, which contain necrotic tissue and again have no tendency to heal.
According to the degree of bacterial contamination of the wound wounds are divided into 3 categories: clean wounds, contaminated wounds, infected wounds.
Clean wounds.
Refers to wounds that are not infected with bacteria and can be healed up to stage I; contaminated wounds: refers to wounds that are contaminated with foreign bodies or bacteria and are not infected, and can be healed up to stage I with proper early treatment; infected wounds: includes surgical incisions with secondary infection, wounds that have been infected and septic for a longer period of time after injury, which require surgical procedures, such as adequate drainage of wound secretions, removal of necrotic tissue, and enhanced dressing changes to reduce infection and promote wound Healing after the growth of granulation tissue, belongs to stage II healing. According to the cause of injury is divided into: pressure wounds, burns, burns, frostbite, radiation wounds, chemical wounds, electric shock wounds …….
3, the wound healing process is divided into four phases.
(1) coagulation period
(2) inflammation period
(3) repair period
(4) maturation period
The process of wound healing is mainly achieved through cell regeneration. Regeneration is the compensation for the loss of tissues and cells, and is therefore the initiation and basis of wound healing. Under normal circumstances, some tissues and cells will be continuously consumed, aged and died, and continuously replenished by the same kind of cell division and proliferation, which is called physiological regeneration, such as the shedding and renewal of epidermis, and the periodic apoptosis and replenishment of blood cells. It is characterized by the complete maintenance of the original structure and function of the regenerated cells, so it is called complete regeneration. The regeneration after the loss of tissue cells due to injury is called pathological regeneration or reparative regeneration.
When the wound is superficial and the loss of tissue cells is slight, it can be supplemented by dividing and proliferating tissue cells of the same species to make it have the same structure and function, forming a complete pathological regeneration; it is seen in wounds with intact epidermal basement membrane such as skin abrasions and first-degree burns. However, when more tissue cells are missing, the organism is often repaired by another replacement tissue —– connective tissue to fill in, so that it loses the structure and function of the original tissue, forming an incomplete pathological regeneration. The vast majority of clinical cases are of this type of regeneration. Wound healing is based on a series of biological activities of inflammatory cells such as macrophages and neutrophils as well as repair cells such as fibroblasts and epidermal cells, with the involvement of the cellular matrix.
One of the wound processes coagulation phase
From the moment of wound formation, the first response of the organism is its own hemostatic process. This process includes some very complex biological reactions: first, the small vessels and capillaries around the wound surface reactively constrict to reduce local blood flow, and then the exposed collagen fibers attract platelets to aggregate and form clots; subsequently, platelets release vasoactive substances such as 5-hydroxytryptamine and prostaglandins, which further constrict the blood vessels and slow down blood flow, while the released phospholipids and ADP will attract more more platelet aggregation. Finally, endogenous and exogenous coagulation processes will be initiated. Once the coagulation process is complete, the body begins to heal the wound.
Wound Process II Inflammatory Phase
This period starts from the first 2-3 days of trauma formation. Local vasoconstriction leads to local tissue ischemia, causing the release of histamine and other vasoactive substances, which cause local vasodilatation of the wound; at the same time, the presence of necrotic tissue and possibly pathogenic microorganisms triggers the body’s defense reaction (inflammatory response): immune cells such as granulocytes and macrophages move and concentrate towards the wound. On the one hand, granulocytes prevent or engulf invading bacteria, while on the other hand, macrophages engulf and digest necrotic tissue cell fragments, while their own proteolytic enzymes released after tissue cell destruction can also digest and dissolve necrotic tissue cell fragments, leaving the wound surface clean in order to initiate the tissue repair process.
In addition to phagocytosis and digestion of tissue cell debris, macrophages are also key factors in stimulating fibroblasts to proliferate and differentiate to synthesize collagen. This process is also known as the cleansing phase. At the same time, the trauma surface will reactively contract with a view to reducing the trauma area. Clinically, this is also known as the black phase because most of the wounds in this period are covered by black necrotic tissue. When this layer of necrotic tissue is removed, the wound is still covered by a thin layer of decaying inactivated tissue, giving the wound a yellow appearance, hence the clinical staging often refers to the wound as the yellow phase.
Wound process of the third repair period
This period can be divided into 2 stages: Epithelialisation and Granulation. It is also called the Proliferation phase. This period lasts from about 2-24 days after the formation of the wound.
Epithelial cell regeneration
Wound repair begins with the proliferation of surviving basal cells at the perimeter of the wound and their migration to the center. At the same time, the proliferation of basal cells stimulates a reactive proliferation of capillaries and connective tissue at the base of the wound. When the wound is covered with new epithelial cells, the wound has a pink appearance, which is why it is also called the pink phase. Granulation tissue formation
Subsequently, the proliferation of basal cells stimulates the growth of granulation tissue. At the same time, macrophages release growth factors such as platelet-derived growth factor (PDGF), β-transformed growth factor (β-TGF) and α-transformed growth factor (α-TGF), which accelerate granulation tissue formation.
The formation of granulation tissue has important biological significance, mainly in terms of.
(1) filling tissue defects
(2) Protecting the wound surface from bacterial infection and reducing bleeding
(3) Mechanization of blood clots, necrotic tissue and other foreign bodies
Because of the bright red appearance of the new healthy granulation tissue, the wound is clinically referred to as the red phase at this time. With the continuous formation of granulation tissue, the lack of wound tissue is filled and the epithelial cells move from the circumference of the wound to the center, eventually allowing the wound to be completely covered by regenerated epithelial cells.
Maturation phase of the wound healing process
However, when the wound is completely covered by the regenerated epithelial cells, the healing process is not completely finished. This is the maturation phase of the wound. Because the new granulation tissue and epithelial cells need to further divide and differentiate, transform and strengthen before the wound can finally heal completely.
This process is manifested in 2 main ways.
(1) The newly formed epithelial cells keep dividing and thickening the epidermal layer.
(2) Internal transformation of the granulation tissue: the formation of collagen fibers changes, increasing the strength of the new connective tissue; at the same time, the number of capillaries decreases, causing the local color of the wound to fade and approach normal color.
(3) This process takes a long time, often more than 1 year. Before the wound healing is complete and mature, the wound is still vulnerable to re-injury, and this period is often overlooked by patients and medical personnel because the wound is apparently completely healed. This is why, clinically, chronic trauma often occurs in the same area.
Wound healing has also been divided into three phases.
Inflammatory phase
The main cells involved: platelets, neutrophils and macrophages
Phenomena of cellular activity: coagulation, inflammatory response
Characteristics of the wound: redness, swelling, heat, pain
Duration: 0-3 days
Proliferative phase
Main participating cells: macrophages, fibroblasts and epithelial cells
Phenomena of cellular activity: granulation tissue appears, wound fills and shrinks, epithelial cells regenerate
Duration: 1-21 days
Wound characteristics: bright red color, wound shrinkage, epithelial proliferation covering
Maturation phase
Main participating cells: macrophages, collagen
Cellular activity phenomenon: vascular atrophy, collagen reorganization
Wound characteristics: wound scar contraction, epithelial coverage complete, lighter in color, increased resistance to tensile forces
Duration: 21 days to several years
4.New theory of wound healing–wet healing theory
The humidity of the wound wound has a very obvious effect on the healing process of the wound. This has been verified not only in animal experiments, but also in decades of clinical care practice. The mechanisms are manifold.
Facilitates the dissolution of necrotic tissue
Removal of necrotic tissue is the first step in wound healing. In a wet environment, necrotic tissue can be hydrated by exudate and release fibrinolytic enzymes and other proteolytic enzymes from tissue cells, which can hydrolyze necrotic tissue and facilitate absorption to achieve a clearing effect. Fibrinolytic enzymes can dissolve this fibrous sheath and normalize the nutrient exchange between blood and tissues. In addition, the protein degradation product FDP is also a chemotactic factor for immune cells, which can attract immune cells to move to the wound surface and accelerate the debridement process.
Maintaining the hypoxic state of the local microenvironment of the trauma surface
Since the wet environment is often formed beneath closed dressings, and beneath such closed dressings, the local microenvironment of the trauma often develops hypoxic tension. Studies have demonstrated that the relative hypoxic environment results in the fastest growth of fibroblasts and stimulates the release of multiple growth factors from macrophages. It accelerates the formation of blood vessels, thus accelerating the formation of granulation tissue and shortening the wound healing time.
Facilitates cell proliferation and differentiation and migration
Water is needed as a medium for cell proliferation and differentiation as well as enzyme activity, therefore, a moist environment can maintain cell and enzyme activity, which will help the wound healing; at the same time, the cells can migrate more rapidly in a moist environment.
Retaining active substances in exudate and promoting their release
Wound exudate contains various growth factors such as PDGF and β-TGF, which play an important role in regulating the wound healing process. They not only stimulate fibroblast proliferation, but also act as chemotactic agents for macrophages, neutrophils and smooth muscle cells.
Reducing the chance of infection
As mentioned earlier, the wet environment is established under occlusive dressings. Due to the characteristics inherent to closed dressings, which act as a barrier to microorganisms in the external environment, clinical applications have shown that: in this condition, the infection rate of the wound is only 2.6%, which is a significant reduction in the chance of infection (7.1%) compared to the traditional method of wound management (dry).
No formation of dry scabs, avoiding mechanical re-injury to the wound during dressing changes
The moist environment prevents the formation of dry scabs due to excessive evaporation of exudate from the wound, thus preventing mechanical re-injury during dressing changes and facilitating wound healing. At the same time, the moist environment makes the nerve endings of the trauma not directly exposed to the air and feel pain, thus making the patient feel relaxed and thus indirectly promoting the healing of the trauma.