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The TIME Model: Overview

Established over a decade ago, the acronym TIME still demonstrates the basic principles integral to an organized approach to wound bed preparation.1 This approach allows the clinician to go through the assessment process to keep the wound healing or take a chronic or delayed wound and get it moving forward again. The “T” stands for tissue or removal of devitalized tissue or foreign material and debris from the wound bed. This can be accomplished by either appropriate cleansing or some type of debridement. “I” stands for infection and inflammation management. “M” stands for moisture and keeping the wound bed optimally moist, avoiding desiccation or too much moisture. Finally, “E” stands for edge and refers to keeping the edges moving across the wound bed toward achieving closure.
Wound bed preparation includes identifying the etiology of the problem, then reviewing all the cofactors and comorbidities that may inhibit or delay the healing process. The next step is to implement interventions and make appropriate referrals. Realistic goals need to be set for wound care, to implement the appropriate plan of care. Is the wound healable? This would be an individual whose body can support the phases of wound healing within an expected time frame. The treatment should be aggressive to prevent any delay that could cause the wound potentially to stall or become chronic. If the wound is expected only to be maintained, the goal is to keep a wound from deteriorating by providing comprehensive wound care. There can be situations when the wound is not expected to heal, such as when the patient is receiving hospice or palliative care. When the individual cannot support the phases of wound healing within an expected time, comfort is more important than cure.


Before any dressing change and before any assessment,

  • the wound be should be cleansed. Wound cleansing removes surface debris, contaminants, and toxins from the wound bed and is a key measure to controlling bioburden.
  • The process should provide adequate cleansing while minimizing any chemical or mechanical trauma, but it should also be aggressive enough to remove any foreign material or devitalized tissue that can impede wound healing.

Wound cleansers are available commercially and typically use surfactants to help reduce surface tension and release debris from the wound bed. Some commercial cleansers contain ingredients that help reduce bacteria such as benzethonium chloride, polyhexamethylene biguanide, or hypochlorous acid. Ingredients such as povidone-iodine, chlorhexidine, hydrogen peroxide, and acetic acid have been shown to interfere with fibroblast proliferation and epithelial growth.These substances are found in many skin cleansers and soaps, and they should be used only on the skin because they are not intended for use in the wound bed.

“So, once the wound is cleansed, what needs to be debrided?

Most obvious would be any necrotic tissue, such as slough or eschar.” So, once the wound is cleansed, what needs to be debrided? Most obvious would be any necrotic tissue, such as slough or eschar. Slough may be thin and stringy or thick and fibrous, and it often has a sticky appearance. Slough may be yellow, tan, gray, green, or brown and is often the result of protein, fibrin strands, and dead cells that naturally collect in the wound bed. It may cover all or part of the wound bed or appear patchy across the wound bed. Because slough is known to slow or even prevent wound healing, once it is removed wounds typically heal faster. Eschar is dead tissue and is found only in full-thickness wounds. It may be tan, brown, or black. Intact stable eschar without erythema, drainage, or fluctuance should not be removed because it is a biological dressing keeping bacteria out and protecting the underlying tissue, which has poor blood flow and is susceptible to infection. Should the eschar become loose, wet and draining, or boggy, edematous, or red, then debridement is necessary. Eschar is not a “scab.” A scab is the crusty coagulation of blood, lymphatic fluid, and exudate found on superficial or partial-thickness wounds. Other substances that need to be debrided include senescent or aberrant cells (which unfortunately cannot be visualized), foreign material that inhibits healing such as dressing residue, animal hair or dander, suture material, or any other type of debris.
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Why should wounds be debrided?

Preparing the wound bed allows for good visual access to assess the wound appropriately, to determine the depth of tissue damage and in the case of pressure injuries or ulcers make it possible to stage the wound accurately. Debridement is necessary for the proper removal of necrotic tissue or senescent or aberrant cells that may harbor bacteria, increase the risk of infection, delay the healing process, impair macrophage function, and physically splint the wound open. Before debridement, it is important to identify who is able to perform the debridement based on experience and qualifications. Special considerations that should be taken into account may include the condition of the patient, the cost of the products, the therapeutic effectiveness, how efficient the procedure might be, and what resources are available.

There are several ways to achieve debridement of the wound bed

including sharp surgical debridement, conservative sharp debridement, and mechanical, enzymatic, biological, or autolytic debridement.
Sharp debridement is performed under sterile conditions in the operating room and is the most effective and efficient way of converting a chronic wound to an acute wound and restarting the healing process.
Conservative sharp debridement is done outside the operating room, and although it removes necrotic tissue and debris, it is not as aggressive a procedure as surgical sharp debridement. During conservative sharp debridement, the practitioner can clearly identify devitalized tissue above the level of viable tissue by using sharp instruments, including scalpels, curettes, and scissors.6 With this method, repeated debridement is often needed; however, minimal pain and bleeding should be expected.
“During conservative sharp debridement, the practitioner can clearly identify devitalized tissue above the level of viable tissue by using sharp instruments, including scalpels, curettes, and scissors.”
Mechanical debridement is a non-selective method of physically removing non-viable tissue and debris; however, it also can remove viable tissue at the same time. Mechanical debridement methods include wet-to-dry dressings, wound irrigation, or pulsed lavage.
Thesemethods are costly, time consuming, and labor intensive because of the time required to perform them. Mechanical debridement can also cause pain, bleeding, and additional wound trauma.
Enzymatic debridement is achieved with the use of exogenous proteolytic enzymes, which work directly on devitalized tissue or indirectly by dissolving the collagen that attaches the devitalized tissue to the wound bed. When using an enzymatic agent on eschar, it is necessary to cross-hatch or score the eschar to help with the mechanism of debridement.
Biological or larval debridement is the application of sterile, medical-grade larvae or maggots into the wound bed. The larvae are selective and remove only devitalized tissue while disinfecting the wound bed and thus promote wound healing.
Autolytic debridement is a selective process by which endogenous phagocytic cells and proteolytic enzymes break down necrotic tissue. This process occurs in varying degrees in the presence of a moist wound healing environment and is dependent on the patient’s having a functioning immune system.

IInfection or Inflammation

The “I” in TIME stands for infection or inflammation management. It is important to remember that all wounds are contaminated with microorganisms. Low levels of bacteria can actually stimulate wounds to repair themselves. It is when these organisms increase in the wound bed that healing slows and wound repair is severely retarded or halted altogether. Increased levels of bacteria can prolong the inflammatory phase of healing and result in further tissue damage.7 If bacterial load is determined to be of a sufficient level to be considered infection, this can also delay wound healing. This makes it important to understand the difference between normal wound inflammation and the progression of contamination to infection. Inflammation manifests with an increase in periwound erythema (redness), warmth, pain, and edema; however, the clinical signs and symptoms of infection can be very similar.
Wound contamination is the presence of non-replicating bacteria in the wound. The host remains in control of the environment, and healing is not impaired by these bacteria. When effective wound bed preparation is not completed and wounds are not managed well, bacteria will begin to replicate. If there is an increase in the number of bacteria, depending on the virulence of those bacteria, this process can begin to overwhelm the host.
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Critical colonization concepts were developed to describe the idea that bacteria may play a role in non- healing wounds that do not have any signs and symptoms of obvious infection. In reality this concept most likely describes the presence of biofilm. In wound infection, there is a presence of replicating bacteria that invade both the superficial tissue and the deep tissue, with the host showing a local or systemic reaction. Assessment of chronic wound infection is a clinical skill and requires good decision making on when to prescribe or apply antibiotics or apply topical antimicrobial agents.
“Assessment of chronic wound infection is a clinical skill and requires good decision making on when to prescribe or apply antibiotics or apply topical antimicrobial agents.”
Superficial infection may manifest as a delay in healing with only islands of granulation tissue or granulation tissue that is abnormal in appearance, with discoloration, friability, or a flat and smooth surface. There may be eroding wound edges, an increase of drainage, necrotic tissue, or debris in the wound, pocketing at the wound base, or an abnormal odour. Peri-wound indicators are helpful in determining wound status. Normally in the inflammatory phase, which occurs during the first one to five days of wounding, erythema is noted and may extend as far as 5cm. Periwound erythema after five days that is greater than 5cm may be an indication of cellulitis. If tracking of the erythema away from the wound bed occurs, this is considered a pathological response and may indicate a systemic issue. Symptoms of systemic infection may include elevated temperature, increased white blood cell count, elevated glucose levels, malaise, or a change in level of consciousness.
“Symptoms of systemic infection may include elevated temperature, increased white blood cell count, elevated glucose levels, malaise, or a change in level of consciousness. ”
Addressing increased bioburden begins with increasing the frequency and aggressiveness of wound cleansing. Commercial wound cleansers or antimicrobial wound cleansers should be delivered at a psi (pounds per square inch) that facilitates appropriate cleansing. The wound should be closely monitored for improvement; if none is seen, then reassessment for any additional pathological findings should be conducted.
Frequently, biofilm in the wound may be a factor delaying wound healing. Biofilm is a complex microbial community containing bacteria and fungi. The microorganisms synthesize and secrete a protective matrix that enables firm attachment to a living or non-living surface. Biofilm has been found to form on surfaces of medical devices and wounds. Biofilms exist in 60% of chronic wounds and 6% of acute wounds and contribute to underlying wound infection, chronic inflammation, and delays in wound healing. These all occur because the biofilm stimulates a chronic inflammatory response that increases exudate, neutrophils, macrophages, proteases, and reactive oxygen species, which can damage normal and healing tissue.
Biofilm forms in different stages. Stage 1 is when the microoganisms have a reversible attachment. They can attach in a matter of minutes, form microcolonies within four hours, and become biocide tolerant within 12 hours. In stage 2, the biofilm has permanently attached to the wound bed. Stage 3 is a slimy protective matrix, or biofilm. Treatment should always be of high importance and begin with aggressive cleansing and debridement. Appropriate dressings can then be used to prevent bacteria from entering the wound bed, and antimicrobial dressings will help kill the bacteria in the wound bed. Remember that topical antibiotics should be avoided because of the risk of developing drug resistance.11


The “M” in TIME is for moisture management. It has long been recognized that maintaining an optimal moisture balance in a wound is critical to the healing process. A wound is a disruption or alteration of the skin’s architecture, structure, and function. When wounding occurs, the healing cascade begins and hopefully the wound will move through the normal stages of wound healing, which are the inflammatory, proliferative, and maturation phases. For optimal healing, the wound should have good vascularity and be clean and free of devitalized tissue and debris, clear of infection, and moist. The single most impactful part of wound care in maintaining a moist wound healing environment is the choice of wound dressing.
The wound healing process is complicated, and as a pathophysiological process, one of the primary essential components is a balanced microenvironment. That cellular microenvironment is fluid, and after an injury the evaporative water loss can be as high as 20 times greater than that of intact skin. Air exposure leads to wound bed dehydration, desiccation, and scab formation. Although the scab’s aim is to protect from infection, this dry or low-moisture microenvironment leads to cell death and delayed wound healing.
In years past the focus in making and choosing dressings was on reducing moisture and drainage.
Now, with a heightened awareness of the importance of moist wound healing, the focus has been on developing advanced wound dressings that maintain a moist wound healing environment. That said, in TIME, the best way to manage moisture in wounds is primarily through choosing the right dressing that meets the needs of the wound identified in the assessment. Critical to the healing process is the balance of moisture, which is accomplished by the dressing’s ability to control water vapor evaporation from the wound bed and promote healing. Interactive dressings are capable of working with wound properties such as wound exudate, tissues, cells, and growth factors while optimizing the wound environment. Dressings should be cost-effective as well as easy to use by the health care professional, family, or alternate caregiver.
“Critical to the healing process isthe balance of moisture, which is accomplished by the dressing’s ability to control water vapor evaporation from the wound bed and promote healing.”


The “E” in TIME is for the edge environment of the wound. As wounds heal and fill in with granulation tissue, they also contract and attain closure via epithelial cell migration across the surface of the wound. If a wound becomes stuck or healing stalls, then more aggressive debridement may be needed to return the wound to an acute state of injury and restart the healing process. There may be a need for more advanced therapies essentially to “kick start” the healing process.
Getting wound edges to advance is essential to wound healing, and it is important to protect the wound margins. Although maintaining optimal moisture may be key to making this happen, there is also the possibility that the presence of excessive amounts of biological components or proteases present in the wound exudate may impede healing and cause the wound to stall. The wound care provider must observe for signs of maceration, dehydration, undermining, or epibole (rolling under), which will impact the ability of the wound edges to advance and close. This information is then used to make informed decisions on wound management therapies and topical dressing selection to promote wound closure.

“Getting wound edges to advance is essential to wound healing”

Proposed expansions to the TIME mnemonic would recommend a more holistic view of wound care. While the current version focuses on assessment and management of the wound tissues, the updated versions include recommendations for managing comorbidities and social factors as well.
One such update was created by a recent consensus panel, who recommended updating the mnemonic to “TIMERS”; the R would stand for regeneration/repair of tissue and the S for social factors. These two factors expand the scope of holistic patient care to encompass additional components that may have an impact on healing. They may also help to better identify where advanced adjunctive therapies should be considered as a part of the standard of care. Another recommended update is the TIME Clinical Decision Support Tool. This update adds an ABCDE care cycle to help clinicians determine the appropriate next step at each stage of wound healing.
• Assess Patient, wellbeing, and wound
• Bring in multi-disciplinary team and informal careers to promote holistic patient care • Control or treat underlying causes and barrier to wound healing
• Decide appropriate treatment
• Evaluate and reassess the treatment and wound management outcomes.
Each of these components should be individually addressed and readdressed during each step of clinical decision makng.

Five Principles of Wound Healing

Utilization of the Five Principles of Wound Healing will aid in appropriate dressing choices.15

1. Wound healing principle

Is the wound healing?
If the answer is yes, then proceed with best practice treatment. If the answer is no, then consider other etiologies, critical factors affecting wound closure, or bioburden. Is healing stalled or slowed and needing to be “kick started”? Are there issues with pain that prevent the patient from complying with the treatment regimen or are there other reasons for non-compliance (for example, the patient does not want to have the dressing changed or to look at the wound).

 2. Wound healing principle

Is there an optimal amount of moisture and is there an odor?
If the wound is wet, then dressing choice should be focused on absorption. Drainage levels should start to decrease as the wound moves from the inflammatory phase to the proliferative phase of healing. Is there an unusual odor? Is it in line with the odor of normal wound drainage? Does the odor dissipate with wound cleansing and debridement? On the other hand, is the wound dry? If so, utilizing dressings that donate moisture and/or maintain a moist wound environment would be the best choice. Epidermal cells migrate more easily and more quickly in a moist wound environment. When the wound is dry, the cells have to burrow to find moisture that will make migration possible.

3. Wound healing principle

Understand the periwound skin
The periwound skin should be without redness, edema, or pain and should have evidence of epithelial migration beginning. Assessment parameters should include looking for evidence of skin issues caused by medical adhesives. If these issues exist, then other securement devices or another type of tape should be considered. Other considerations include adhesive removers, silicone-based tapes and barriers, and skin sealants as appropriate.

4. Wound healing principle

Is the tissue necrotic, senescent, or viable?
If the tissue is necrotic, it should be debrided if that is consistent with the overall goals of treatment. If the cells are senescent, then consider debridement followed by the use of antimicrobials. If the tissue is viable and progressing, then the treatment regimen should continue to support wound repair.

5. Wound healing principle

Is there depth or dead space?
Dead space needs to be filled so that the wound heals from the inside out. This also helps ensure that pockets do not form, which can result in abscess formation and further delay in healing. If the wound is flat, then cover it with the appropriate moisture retentive dressing.


Remember that prevention is our goal above all else, and keep the patient and family involved and active in decision making. An accurate and complete assessment helps to set realistic goals for each patient, including an understanding of the expected time to healing. Early, appropriate, and aggressive interventions help keep wounds on a healing trajectory. Follow the principles of wound healing and implement a comprehensive plan of care that includes cleansing, debridement, maintaining a moist wound environment, and reassessing the wound and the individual with any change in condition. Dressings and other products utilized should be not only clinically effective and efficient, but cost-effective as well. Following the wound healing principles demonstrated by TIME helps maintain an organized approach to addressing the needs of wounds and achieving positive outcomes.

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