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A pressure injury is a result of prolonged force applied to the skin and underlying tissue from the individual's body weight and the surface in contact with the skin; over time, this can lead to the degradation of the skin and tissue. Pressure injuries primarily occur in areas with thin layers of tissue and are commonly affected by pressure. Areas such as the heels, elbows, tailbone, and shoulder blades are bony prominences that are at a greater risk of developing pressure injuries. Pressure injuries can also be caused by medical instruments such as nasal prongs, tubes, compression wraps, and splints. (Mondragon & Zito, 2024)

Pressure injuries can occur in any age or gender; however, they are much more prevalent in people with poor or limited mobility and people with compromised or fragile skin.

Pressure injuries are categorized by the severity of damage done to the tissue.

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How sheer pressures and friction can result in the development of pressure injuries

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How sheer pressures and friction can result in the development of pressure injuries

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The constant pressure applied to the skin tissue can compress blood vessels in the integumentary system. These blood vessels provide nutrients and supply oxygen to the cells that form the tissue. Over time, the blocked blood vessels in the tissue will result in ischemia. Ischemia is the occlusion of blood flow to all forms of tissue.

Ischemia is reversible; however, if left untreated, it can develop into hypoxia, which is tissue damage caused by a deprivation of oxygen to the cells.

(WebMD, 2017)

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There are many types of mechanisms for cellular injury such as: Hypoxic Injury, Calcium Imbalance, and damage caused by oxygen or oxygen-derived free radicals. These mechanisms of injury are responsible for the degradation of tissue, which can result in the development of wounds.

Blood transports oxygen from the lungs through the blood vessels to the body's cells. Cells require oxygen to produce aerobic adenosine triphosphate (ATP), which serves as the primary energy source for cellular function in the body. (Mallat et al., 2022)

ATP is created by the organelle mitochondria through cellular respiration. Without ATP, cells are not able to maintain the necessary metabolic reactions required to promote cell function, regulate electrolytes and muscle contraction. When aerobic ATP production (cellular respiration) is impaired, the body switches to anerobic ATP production, which is less efficient and results in the production of less ATP (Baker, 2020)

ATP is the primary energy source in DNA synthesis, which is key in cell replication. The decrease compromises DNA synthesis, which can result in cell death. Due to impaired DNA production, ultimately, the cells cannot replicate to replace damaged cells. Prolonged oxygen deprivation from ischemia will result in hypoxic injury, which is caused by the absence of oxygen in the cells, resulting in depleted ATP sources, which will result in a loss of cell membrane integrity, disrupted cellular homeostasis, and eventually, tissue necrosis.

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When the cell membrane is compromised, it can result in an influx of extracellular molecules, such as calcium entering the cell. This occurs due to the natural concentration gradient where molecules in the body from a level of high concentration will move to areas of low concentration to maintain homeostasis in the body. In this case extracellular calcium can enter the cell, increasing intracellular calcium concentration. The increase in calcium within the cell can result in cell injury through the following ways.

A significant increase in intracellular calcium can cause damage to organelles such as the mitochondria, which is responsible for ATP production. The increased calcium concentration can cause the breakdown of the cell membrane and also activate harmful enzymes that could damage the cell.

significant levels of calcium found in the body is call Hypercalcaemia and is harmful if left untreated.

(Trump et al., 1980)

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How oxygen and oxygen-derived free radicals cause damage to the cells.

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How oxygen and oxygen-derived free radicals cause damage to the cells.

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free radicals are the natural byproduct of the metabolism, however, when there is an imbalance of anything in the body, it can cause harmful effects. Oxidative stress is the result of an imbalance of oxygen-derived free radicals within the body.

(cleveland clinic, 2024)

The increase in free radicals can overwhelm the homeostatic control of the body, leading to damaged cells and degradation of the cell membrane, resulting in loss of structural integrity of the cell and tissue damage.

free radicals are unstable molecules due to them missing an electron. In an attempt to stabilize themselves, they try to take an electron from another atom or molecule within cells. The removal of these molecules from the cells results in cellular damage that results in cell damage and eventual cell death. Free radicals can damage the DNA within cells, effectively mutating the cell's ability to replicate. Under normal circumstances, if a cell is detected with a DNA mutation, it can be detected by the tumor suppressor genes in our body, which can force the mutated cell to initiate apoptosis if the DNA mutation cannot be fixed. A DNA mutation can become carcinogenic due to its ability to spread and multiply without control. This can result in the development of malignant tumors or cancer.

(Cleveland Clinic, 2022)

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(Structure and Function of Skin: Skin Layer and Diagram, 2023)

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The integumentary system is the first line of defense against foreign pathogens and a barrier to the external environment. The Integumentary system is primarily made up of the skin; however, it also involves the nails, hair, and certain glands.

The Skin has three primary layers

the Epidermis, Dermis, and Hypodermis.

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The Epidermis is the external layer of the skin. It consists of layers called the stratum: corneum, granulosum, spinosum, and basale, and on specific locations such as the palm and the soles of the feet, an extra layer is present called the stratum lucideum. These are 5 layers of stratified squamous epithelial cells, which make up the epidermis. The epidermis does not have a source of blood supply to receive its nutrients, such as capillaries; it instead receives them from the second primary layer of the skin, the dermis. (Kim & Dao, 2023)

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The Dermis is comprised of the superficial papillary layer and the reticular layer, both of which have different roles in maintaining the homeostasis of the skin. The superficial papillary layer forms the dermal papillae, which are loose vascular connective tissue protrusions that help provide nutrients to the epidermis. The reticular layer is comprised of dense connective tissue, which helps provide structural integrity. In its entirety, the dermis contains essential components such as glands, nerves, blood, follicles and vessels within it. (Kim & Dao, 2023)

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The Hypodermis, the deepest layer of the skin as an anchor to the skin and underlying tissue. The hypodermis is comprised of Areolar and Adipose tissue which help provide a form of fuel storage and insulation for the body as well as being a cushioning layer to protect vital organs or muscles from physical trauma. (Kim & Dao, 2023)

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There are 4 stages of a pressure injury growth.

1) The first stage is known as a non-blanchable erythema, which can be identified as a localized redness in the tissue that does not turn white when pressure is applied. The affected area can present differently to the surrounding tissue, such as increases or decreases in temperature, being more firm or soft, and being painful to individuals. In people with darker skin tones, skin discoloration may be more difficult to identify. These signs may indicate that the patient is at risk of developing a pressure injury. (Clinical Excellence Commission, 2012)

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2) The second stage of a pressure injury can be seen as a shallow open wound due to a partial degradation in the dermis. at this stage wound bed will be present, appearing as an ulcer, or it can also appear as an unruptured blister. The wound bed may appear moist, dry, and shallow. It is Important to note that no bruising or slough should be present in this stage; otherwise, it would indicate that the wound has progressed further. Stage 2 Pressure injuries can be quick to heal if treated immediately and properly. however, this stage can be prone to infection since the bodies first line of defense is compromised.(Clinical Excellence Commission, 2012)

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3) The third Stage of pressure injury can be indicated as degradation of the epidermis and dermis layer of the skin and has reached the hypodermis or subcutaneous layer. A buildup of dead tissue, known as slough, may be present as a moist white or yellowish surface on the wound bed. The depth of the stage three pressure injuries is different depending on the area in which they develop. In Areas with less layers of body fat, the wound bed may still be considered shallow, and in areas with higher layers of fat, the wound bed will appear deeper; however, tunneling of the wound and undermining may occur in both. At this stage, underlying tissues such as bones, muscles, and tendons should not be visibly present.

(Clinical Excellence Commission, 2012)

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A stage four pressure Injury is present as complete degradation of the skin and visible presence of muscle, bone, or tendon.

At this stage, an increase in slough and exudate may appear on the wound bed. Similar to stage three, the depth of the pressure injury varies in depth depending on the thickness of fat tissue in the area it developed on. Stage four pressure Injuries can spread and directly damage deeper tissues causing severe tissue necrosis. (Clinical Excellence Commission, 2012)

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Unstageable Pressure injuries are identified when the depth of the wound bed cannot be determined due to the buildup of dead tissue cells in forms such as slough or eschar filling the depth of the wound's bed. At this stage, the wound will appear dark brown, dry, and solid in form. The presence of eschar in the wound can act similarly to a scab and should not be removed.

(Clinical Excellence Commission, 2012)

Deep tissue injuries have not yet broken the external layers of the skin; however, they may appear as a blister. They are dark in appearance due to the damage done in the underlying tissue. Deep tissue injuries may vary in tissue texture and temperature compared to the surrounding healthy tissue. (Clinical Excellence Commission, 2012)

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(Septicemia | What Are the Symptoms of Blood Poisoning? | BASS Medical Group, 2021)

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Infection occurs when a harmful microbial organism enters and spreads throughout the body, having a detrimental effect on the body's homeostatic state. These organisms can come in many forms such as viruses, bacteria, parasitic organisms, and fungi, some being harmful while others can be beneficial to the body.

Viruses require the use of a host organism to replicate and survive since they use the body's cellular systems to gain nutrients and multiply before spreading to other hosts.

(nhmrc, 2018)

Bacteria can be found in almost every environment, most of which are harmless, even providing benefits such as assisting in breaking down nutrients within the body. Others can infiltrate and multiply within the body, resulting in harmful diseases that can damage cellular function.

(nhmrc, 2018)

Much like viruses, parasitic organisms require the use of a host to survive and multiply; however, parasites are multicellular organisms, whereas viruses are noncellular organisms, hence why they require the use of a host to replicate.

(nhmrc, 2018)

Fungal infections are more potent in people with compromised immune systems; however, they can still have detrimental effects on most people. Fungal infections primarily affect the integumentary system however, they can spread and multiply to other organs and internal systems.

(Cleveland clinic, 2022)

These sources of infections are usually stopped by the body's first layer of defense, the skin; however, if the skin is compromised, such as the presence of a pressure injury where the underlying tissue is exposed, the sensitive internal environment of the body becomes much more susceptible to the external environment, making it vulnerable to microorganisms causing infection.

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Wounds can become infected through a multitude of ways, such as direct contact, airborne viruses, and droplet contact with the wound. The wound can become infected during the creation of the wound or throughout its development.

(Britainnica, n.d.)

Multiple physical manifestations can appear and indicate that the wound is infected. Physical manifestations such as swelling, erythema, increased pain, increased temperature, pleurant drainage (pus), and fever are signs and symptoms of infections. These manifestations are caused by the body's immune system triggering the inflammatory response upon contact with the infection.

(Harding, 2019)

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There are four stages of wound healing after tissue damage has occurred.

The first stage of wound healing is hemostasis. This stage occurs to decrease blood loss and prevent foreign bodies from entering the blood stream through the wound, usually occurring 30 minutes post injury, vasoconstriction occurs, reducing the blood flow to the site of injury. At the site of injury, the extracellular matrix will release cytokines and inflammatory markers that will promote platelet thrombosis to develop clots to prevent further loss of blood and decrease permeability to the wound.

(LaPelusa & Dave, 2023)

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The primary function of inflammation is to prevent the development of infection, which can occur through a multitude of stimuli such as tissue damage, the presence of pathogens, and chemical signals released by other body systems. When cells become damaged, they release chemokines. These chemokines activate mast cells and trigger the release of histamines; the histamines then signal the endothelial cells in which line the blood vessels to expand, resulting in vasodilation. Vasodilation increases fluid levels at the site of injury and also increases vascular permeability. Increased permeability allows for diapedesis, allowing white blood cells to enter the site of injury. At this stage white blood cells can combat pathogens through phagocytosis.

(Stone et al., 2024)

The increased fluid levels caused by vasodilation result in the cardinal signs of inflammation. Swelling is caused by the influx of fluid to the affected area, This swelling also increases pressure on nerves, which results in pain. The increased blood vessel diameter allows for increased blood flow, which causes the erythema since capillaries are dilating. Since more blood is being pumped to the affected area, temperatures increase, which is also beneficial since it can improve cell function and impact foreign pathogens.

(Hannoodee & Nasuruddin, 2024)

Prolonged Inflammation can result in a fever, which is triggered by pyrogens, which signals the body to increase in temperature to prevent the replication of infectious pathogens and improve cellular functions in the body.(Britainnica, n.d.-a)

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In this stage, the body is ready to begin repairing damaged tissue. Fibroblasts enter the site of injury and initiate collagen production. Collagen is required in forming new connective skin tissue to replace the clot created in the hemostasis stage. The cells that make up the dermis then replicate to close the wound. (Teller & White, n.d.)

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The remodeling stage of wound healing can take several years to complete. This stage is where the epithelium recovers and scar tissue develops. Unlike muscle cells when they go through atrophy, scar tissue does not improve in strength; the new scar tissue is weaker than the original. The collagen used in the previous stage will be replaced by a new form of collagen that replicates the same functions as the original tissue.

(Singh et al., 2017)

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Pressure injuries are best treated when they are still in the early stages of development. As nurses, it is essential to understand that all patients are at risk of developing pressure injuries, however, some demographics are more prone to developing pressure injuries and may also take longer to heal from them. As nurses, it is essential to educate patients on the causes of pressure injuries, especially for patients who have mobility issues and patients who are bedridden. most effective way of preventing pressure injuries is to assist patients to mobilize; the frequency of mobilization can vary between patients. Elderly patients or patients, patients with sensitive skin and patients with compromised immune systems are at a greater risk of developing a pressure injury and are more likely to take longer to recover.

If a pressure injury develops, nurses must be able to protect the wound to prevent further degradation or risk of infection. This is done by attending to wound care and applying the most appropriate dressings to the wound. At this stage, the best pharmacological interventions are most likely pain management medication such as NSAIDs and opioids, depending on severity; however, if a wound does become infected, it is best to report it and provide antiviral, antibacterial, or antifungal medication depending on the type of infection. People with diabetes will have more difficulty fending against infections due to fact that diabetes can contribute to a compromised immune system.

(Hommel & Santy-Tomlinson, 2018)