How to Build A Better Scar
Everyone has a scar. And there is usually a story to go with it. Did you ever wonder how that scar developed? Well, the process of wound healing is a complex series of physical, biological and chemical interactions. With the entire human body acting synergistically, we heal without much help. However, in the business of providing durable medical equipment (DME), we often are involved with patients who require more complicated and involved wound healing interventions. These patients with chronic wounds have begun a process which requires a concerted, multi-disciplinary team effort to assist the body's own healing cycle. We play an important role in that process. In other words, to use a common analogy, the rate with which your new home can be built is affected by the contractor's inability to get enough building materials. Our chronic wound patient is analogous with the shell or frame of a house, waiting for a contractor with the connections to get the lumber, plumbing and electrical supplies. They are stuck in a cycle that doesn't allow the wound to close effectively, or get the materials built in the correct order. Our job is to provide the foundation, access to these building materials, supervision and laborers. This will help our patients heal and build a better scar.
It is All in There
What is the correct building process, and how do we assist it? To start, let's define a few terms and processes that are important in wound healing. The skin is the body's largest organ. It comprises about 10 percent of our body weight and serves many functions. The skin provides protection from the constant bombardment of bacteria, insulates the body's internal organs, provides moisture and vapor exchange for temperature regulation, excretes waste products, synthesizes Vitamin D from exposure to sunlight, and provides us with our unique identifying features. The skin consists of two functionally distinct layers, the epidermis and dermis. The epidermis is the very thin, outermost layer and is composed of five distinct subdivisions. These divisions begin with the word stratum and are defined by their cellular shape, size and function. The epidermis generally remodels itself every four to six weeks and does not have a blood supply. The dermis, on the other hand, has all kinds of stuff with which we are familiar. The dermis contains many blood vessels, nerve endings, hair follicles, sense organs, oil and sweat glands and connective tissue. Think about it. Pull a hair from your skin, examine the root, and you can see just how thin these layers truly are. Injury to this very thin covering will require quick and efficient healing mechanisms to prevent opportunistic infections and further damage from occurring. Let's review these processes.
Wound Healing 101
The repair cycle that acute wounds follow is relatively complex, so to better understand the terms and processes, we will use the building contractor analogy addressed earlier. The process of wound healing is signaled to begin immediately following damage to the skin. Because the skin performs many important functions, its damage results in a swift and effective cascade of events. These events follow four normal phases: hemostasis, inflammation, proliferation and remodeling. The first phase, hemostasis, is the process of controlling bleeding. Platelets are attracted to the site by clotting factors (the things that hemophiliacs don't have enough of) and the disrupted blood vessels are immediately repaired. This is necessary to prevent further damage and loss. This initial phase can be greatly affected by medications including aspirin, anticoagulants such as Coumadin, some herbal supplements and over-the-counter anti-inflammatories. The second phase, inflammation, involves providing a clean site to begin repairs. This is accomplished by attracting neutrophils and macrophages (the laborers and supervisor cells). The neutrophils clean up the debris and remove it from the area. The release of histamine begins the inflammatory phase and is equivalent to sending a large crew of workers to do what a team of five can accomplish. This results in inflammation which can impact blood flow and healing. The inflammatory phase typically lasts from four to six days. The macrophages supervise the clean-up and signal the third phase, proliferation, to begin.
The proliferation phase is the process of rebuilding the injured skin with new tissue. In the open wound, the appearance begins to resemble shiny, red granulation tissue. This is called granulation tissue because the immature collagen fibers, among many other things, fill in the area haphazardly and has the appearance of granules. As this tissue continues to fill in, blood vessels also grow (angiogenesis) to supply much needed oxygen and nutrients to help the wound heal. This phase typically lasts for around three to four weeks. During this time, the wound is very susceptible to damage as the new tissue is slowly filling in with granulation tissue and the overlying epithelium is contracting to cover the wound. Using our analogy, the contractor brings in all of the specialists; the framers, roofers, plumbers, electricians and drywallers. These subcontractors work together to complete the job in a particular order. Thus begins the remodeling phase and the final finishing work can begin.
The remodeling phase then continues for up to two more years, decreasing the scar volume and bolstering its strength and flexibility. Now the finish carpenters, cabinet makers, flooring experts and appliances arrive. It is now beginning to look complete. However, in the human body, the tissue that just laid down needs to be strengthened so that it can resist the forces that injured the skin in the first place. This is the most important concept. Even after two years of remodeling, the repaired tissue is still only about 70 percent to 80 percent the strength of the surrounding intact skin. What does that mean? It means that no matter how healthy the patient is, the wound area will still be susceptible to re-injury. We will revisit this concept later.
Now, for healthy people, this is a fairly straightforward process. Unfortunately, the patients we see may not proceed through these phases as rapidly or may stagnate in between stages. What kinds of things can impede the normal wound healing process? Numerous extrinsic and intrinsic (outside and inside the body) risk factors play a large role in reducing the body's effectiveness in healing itself. Intrinsic risk factors include, but are not limited to, age, smoking, cardiovascular disease, history of previous ulcers, hydration, nutrition, poor mobility, lack of sensation and obesity. These factors, often times, are impossible to manage or beyond our roles. Our job as providers of wound healing equipment and supplies, focuses our efforts on minimizing the extrinsic risk factors. Briefly, the key extrinsic risk factors are pressure, shear, friction, moisture and heat. Support surfaces, wound dressings, sheets and coverlets are designed to reduce these detrimental forces that impede healing. How does each impede the wound healing process?
Minimizing the extrinsic risk factors
Pressure is the easiest to understand. The application of pressure to the skin and underlying surfaces causes ischemia (lack of blood flow) to the tissues when body weight combined with gravity exceeds the capillary blood pressure. This most commonly occurs around bony prominences like the sacrum (tailbone), the ischial tuberosities (sitting bones), the greater trochanters (hip bones) or the (calcaneous) heels. Medical support surfaces for the bed, wheelchair, commode chair, etc. are designed to redistribute the high peak pressures so that blood flow is not occluded, or cut off. This concept is very important. The ability of a support surface to facilitate immersion of the patient's body into a product by increasing the surface area effectively decreases all pressures. For example, imagine a petite woman of 120 pounds walking across a frozen pond with a man twice her weight. If the ice were thin, who would fall through first? Of course the man would. But, what if the man wore snowshoes and the woman word stiletto heels? The woman would, this time. The pressure applied by her 120 pounds would be distributed over a very small surface area whereas the man's weight would be distributed over a very large surface area, provided by the snowshoes. Therefore, the design of therapeutic support surfaces maximizes the ability for the patient to immerse into the product and allow the product to envelop their body. These surfaces provide people with very bony bottoms to have much larger surfaces or bigger bottoms, much like the snow shoes in the above example. Interface pressure measurement devices allow us to see these problem areas and work to relieve these areas by redistributing the pressures to other areas. Unfortunately, pressure isn't our only enemy.
Shear and friction forces also impede healing by similar means. Shear forces are caused by transfer of forces between deep tissues and bony prominences in opposite directions. These forces are easy to describe, but very hard to measure. For example, when a patient's head of the bed is raised from flat to upright, the weight transfer due to gravity shifts toward that direction For example, when we raise the head of the bed from flat to upright, due to gravity and movement, the patient's weight is transferred and shifts toward the foot of the bed. Unfortunately, their entire body doesn't shift in that direction (well, maybe sometimes!). The skin has cohesion with the bed sheets, along with gravity, and is held in place while the underlying tissues migrate toward the foot of the bed. This creates a change in the capillary bed in the skin and underlying tissues. This change results in ischemia and tissue death. Friction, on the other hand, happens on the surface of the skin and can negatively affect the epidermis. Friction injuries are often seen on heels, ankles and elbows. The movement of the legs against rough sheets and equipment can create friction wounds in patients with delicate, dehydrated skin. A skin tear is an example of a friction assault. Therefore, prevention measures are often employed in these patients by providing prophylactic skin coverings like transparent dressings that protect these highly susceptible bony prominences.
The last extrinsic risk factors that impede our body's natural healing are heat and moisture. As we all know, after doing dishes, our skin turns white and gets pruny. It is very fragile and cuts easily. Patients with poor temperature regulation (sweating), incontinence and heavily exudating (draining) wounds often have wounds that will similarly become macerated. These wound edges become white and very fragile. Moisture regulation and wicking becomes paramount. The ability to change the climate around the wound so that the excess moisture can be removed without directly exposing the wound to the outside is the goal. The choice of wound dressings that absorb excess moisture, allow vapor exchange while still maintaining a moist wound environment is indicated.
The support surface also can play an important role in managing this microclimate. True low air loss technologies were designed to provide airflow between the patient and the surface that wicks moisture away from the patient. This occurs only when the air flow escapes through the top of the mattress baffles and is contained within a cover that allows the vapor to permeate. This microclimate change also helps in temperature regulation. Direct cool air blowing on the patient may cool the skin too much and cause vasoconstriction (narrowing of blood vessels). The last thing we want is to reduce the amount of blood flow getting to the damaged tissues.
Building the better scar
After reviewing the healing process and the factors that impede this progression, we are still left with a wound that is closed. Scar tissue has filled in the damaged area and contracted. It continues to remodel itself as long as the extrinsic risk factors we just discussed are minimized. The scar tissue is no longer the same as the surrounding skin, muscle and connective tissue, so it reacts to stresses differently. It will also be that way for the rest of the patient's life. That's right, the wound on the patients tailbone that has taken six months to close is going to be at risk for opening again for the rest of their life. Building a better scar requires providing the scar tissue the appropriate environment to remain closed. That means providing adequate blood flow, reducing shear and friction forces, appropriate ambient temperatures and removing any excess moisture. Wound patients require diligence in their turning schedules, incontinence care and pressure management throughout their daily activities. In the business of providing medical equipment, it is our job to make products, services and education available to the patient, family, caregivers and facilities that treat patients with wounds. But it is also important to understand the key concepts behind why some people heal while others have trouble. It is everyone's role in wound healing to help these patients understand these concepts and help them heal and build a better scar.
This article originally appeared in the July 2003 issue of HME Business.