Overview of Negative Pressure Wound Therapy
Negative Pressure Wound Therapy (NPWT) is a method used to enhance the healing of wounds. It works by creating a lower pressure environment in the wound, which helps to lessen inflammation and encourage the development of new tissue, assisting the healing process. This technique can be used in a range of wound types, including open wounds from surgery and diabetic foot ulcers, as well as on closed surgical incisions.
NPWT has come a long way since its earliest use back in the 19th century. The latest version of this system was highlighted by researchers Argenta and Morykwas in 1997, who explained how it works. It involves using a special dressing made of porous foam, over which a controlled suction is applied via a machine. This creates a pressure which is less than the surrounding pressure, by approximately 125mmHg (a unit of pressure).
This method is now commonly used on a variety of open wounds, including things like open fractures, ulcers, and infected wounds. Often referred to as Vacuum-Assisted Closure or “VAC,” it is important that the system is applied correctly by trained professionals, and it’s often done in operating rooms, as the wounds usually also need cleaning and removal of dead tissue in a sterile environment.
More modern versions of the system offer improved features, such as a range of different pressure settings that can be adjusted to suit the type of wound being treated. The foam dressing may be made of either black polyurethane (PU) or white polyvinyl alcohol (PVA). There are also disposable wound VACs available, which are typically used for smaller wounds.
In recent years, NPWT has started being used to help improve healing of closed wounds, like surgical incisions or skin grafts. It helps to reduce swelling and fluid accumulation, and emphasizes the growth of new tissue to foster healing. This method is increasingly being used on closed wounds that are at risk of reopening or getting infected due to inflammation.
One new direction for NPWT is combining it with the addition of a fluid, like saline or an antibiotic solution, directly into the wound. After a period of time allowing for the solution to spread within the wound, the negative pressure is reapplied for several hours. This cycle is then repeated.
NPWT is an important and promising advancement in wound care, with a variety of uses. This information should give you a better understanding of how it works and when it can be used to promote healing.
Anatomy and Physiology of Negative Pressure Wound Therapy
The skin has three main parts: the outer layer or epidermis, the middle layer or dermis, and the inner fatty layer also known as the hypodermis. Further, the epidermis itself contains five sublayers, each with its unique structure and function. These play a key part in the maintenance of the skin, including skin repair.
Let’s try to understand how our skin heals itself when it’s injured. The wound healing process is generally split into acute and chronic phases. In the acute phase, immune cells and various signaling proteins rush to the site of the injury over the first week, initiating inflammation and clotting to prevent blood loss. Then the healing process enters the “proliferation and re-epithelialization” stage where new skin cells and blood vessels are grown.
The newly formed skin cells and blood vessels are collectively called granulation tissue, which marks a transition to the final phase of wound healing, known as the remodeling phase. This phase can last up to two years and is focused on depositing collagen, a vital protein that provides strength and flexibility to the skin. The configuration of this collagen network is mediated by growth-promoting factors, and gives the skin its unique properties.
In contrast, a chronic wound is a wound that hasn’t healed properly over time. This usually happens when the inflammation stage of healing goes on for too long and disrupts the normal healing process. Factors like repetitive stress on the tissue, or an ongoing bacterial infection can contribute to this. Instead of healthy skin, the wound fills up with a lot of inflammation-promoting proteins, scarring tissue, and a surplus of collagen and fibronectin, which makes the skin stiff and less pliable.
Some treatments can help kickstart the healing process again. Negative pressure wound therapy (NPWT) is one of them. Though we have a lot to learn about this therapy, it’s thought to work in a few ways. First, it can shrink the wound space by up to 80% using a suction force of 125 mmHg. Second, this suction also causes miniscule waves on the wound surface, stimulating healthy tissue formation. Third, it helps remove excess inflammatory fluid from the wound, improving circulation in that area. Finally, removing this fluid helps balance the pressure and concentration of proteins in the wound, facilitating healing. Alongside these effects, the warmth provided by the sealed dressing of NPWT gives another boost to wound healing.
Why do People Need Negative Pressure Wound Therapy
Negative pressure wound therapy (NPWT) is a special technique used to speed up the healing of complicated wounds that either don’t heal or might not heal on their own. There are two types of wounds typically treated with this therapy: acute wounds (those which are new and typically severe) and chronic wounds (ones that remain unhealed over time).
NPWT is often used on acute wounds when they can’t be simply stitched up due to a high risk of getting an infection, already being infected, having too much tension on the skin, or swelling. Traumatic wounds like open breaks in the bone or cuts, degloving injuries (where skin is torn off), and burns causing partial loss of skin are common types of acute wounds where NPWT can be beneficial. These wounds have a high risk of getting infected since they are exposed to bacteria from the environment. Stitching it up would trap bacteria inside, leading to an abscess or pus-filled pocket. Additionally, any unhealthy tissue left behind could die off and lead to further tissue loss, worsening the wound. Before using NPWT, surgeons make sure to thoroughly clean and remove any unhealthy tissue from the wound to help new, healthy tissue grow back faster and promote the wound healing.
NPWT is also beneficial for “dehisced wounds”, which are wounds that have opened after surgery, and can be either acute or chronic. NPWT can help protect the wound while reviving the skin around it, thereby helping the wound heal successfully. Similar to this, NPWT can prepare skin for successful grafting, a procedure where a piece of skin taken from another part of the body is transplanted onto the wound.
Another use of NPWT is treating skin breakdown due to ulcers caused by various reasons or treatment of closed wounds, such as surgical cuts including skin flaps and grafts.
When a Person Should Avoid Negative Pressure Wound Therapy
Before using a technique called negative pressure wound therapy, which helps wounds heal by sucking away fluid and other materials, it’s important to thoroughly check the wound to ensure that the therapy won’t harm the patient. This therapy shouldn’t be used if the patient has exposed blood vessels or organs, unopened and unexplored abnormal openings called fistulae, as these can create a serious risk of heavy blood loss or dehydration and electrolyte imbalance.
This therapy may not also work properly if there is dead tissue or a type of scab called eschar in the wound, as seen in severe burns. The presence of dead tissue may lead to more non-healing and further spread of dead tissue. If either of these issues is identified, the wound requires further medical treatment or a different type of dressing.
If cancer is present in the wound area, negative pressure wound therapy should not be used due to the theoretical possibility that it could help the cancer spread. Similarly, if a bone infection, called osteomyelitis, is present and active, ideally, it should be treated before using this therapy. However, there have been cases where the therapy has been used even with active osteomyelitis, with no further damage to the wound.
Equipment used for Negative Pressure Wound Therapy
Here are the things your doctor will need for your treatment:
1. A skin-cleaning substance (2% chlorhexidine in 70% isopropyl alcohol or 7.5% povidone-iodine), commonly known as alcoholic chlorhexidine or betadine.
2. Special sterile sheets (drapes) that will be used to cover the area around where your surgery is taking place. This helps to keep everything clean and germ-free.
3. A set of clean, sterile tools for either a small bone surgery or standard wound care surgery. These kits have all the necessary tools your doctor will need for your procedure.
4. Six liters of a saline solution (0.9% sodium chloride). This is kind of like a salt-water mixture that helps to clean your wound.
5. Sterile pads (gauze) which the doctor uses to soak up any blood or fluids.
6. A special net made of non-paraffinized, coated polyester. This will be used to cover your wound.
7. A pack of tools for a specific type of wound treatment called Negative Pressure Wound Therapy (NPWT):
- A specialized sticky dressing that creates a vacuum seal for closed wounds.
- A specialized foam dressing (either pre-cut or not), which will be used if you have an open wound.
- A transparent sticky tape that helps keep the dressing in place.
- A medical vacuum device used to extract fluid from open wounds and promote healing.
Who is needed to perform Negative Pressure Wound Therapy?
Negative pressure wound therapy is a medical treatment that a range of medical professionals, such as doctors, foot specialists, wound care experts, nurses, experienced nurses, and physician assistants, can undertake. But, it’s crucial they’ve received proper training and gained ample experience beforehand. These requirements are due to the complicated nature of the wounds, which are tough to treat using other methods. If not done properly, the treatment can lead to more problems.
Closed wounds are typically treated by trained health professionals either in a hospital or a clinic. If the wound is a surgical incision or a skin graft, the therapy should be started in the operating room by the surgeon or a surgical nurse. On the other hand, open wounds need surgical management in the operating room at first. As such, one or two surgeons and a trained surgical nurse are needed during the process. After the initial treatment in the operating room, the therapy’s subsequent stages can be carried out in a hospital ward or at a clinic by trained health professionals.
For very complicated cases, with multiple injuries, the treatment may need to take place in an ICU (Intensive Care Unit), a specialized department in a hospital where critically ill patients receive high-level care.
Preparing for Negative Pressure Wound Therapy
Whether a wound is closed or open, it can be treated both inside and outside of the operation room, based on how serious the wound is. First, all the tools required are cleaned and arranged in a contamination-free area. The wound itself is also cleaned with a solution made from alcohol and chlorhexidine (a disinfectant and antiseptic). If the wound is being treated outside an operation room, it needs to be allowed to dry naturally before a special dressing used for negative pressure wound therapy (NPWT) is applied.
If the wound is open, the patient will need to be admitted to the operation room. Before the treatment starts, the patient needs to complete a consent form and safety checklists. The patient and doctor should talk about why the procedure is needed, what the benefits are, and what the risks could be. The conversation should also include how each risk can affect the patient personally.
In the operation room, the surgical scrub nurse prepares all necessary equipment in a clean area. The open wound is cleaned with the alcoholic chlorhexidine solution and then covered by a sterile drape to keep it contamination-free, following standard surgical preparation.
Before the Vacuum Assisted Closure (VAC) device can be applied, any dead or infected tissue left could slow down the process of wound healing through a reduced blood supply to the wound and multiplication of bacteria on it, so, it needs to be removed.
After this cleaning process or ‘debridement’, the wound is rinsed with a good quantity of Sodium Chloride solution (0.9%). Once this is done, sterile gauze is used to dry the wound which is then covered with a sterile wound contact layer that doesn’t stick to the wound or further harm it. Nowadays, a polyester net that is not coated with a paraffin based material is a popular choice for this.
How is Negative Pressure Wound Therapy performed
When treating a patient’s wound, it’s important to position them in a way that properly shows the area to be treated. This whole area will be carefully covered to protect it.
If the wound is closed, a special sticky bandage will be used to cover it. In order to make sure the bandage stays firmly in place, wide pieces of clear, sticky sealing tape are put around its edges. This part of the process is really important if we’re using Negative Pressure Wound Therapy (NPWT), a treatment that uses a vacuum to help heal wounds. Without a tight seal on the bandage, the vacuum won’t work and the treatment won’t be effective.
If the wound is open, a special spongy bandage is used to cover it. This bandage needs to fit the size and shape of the wound exactly, so it might be cut to fit properly or even be available in a ready-made suitable size. The whole wound needs to be covered by this bandage. If the wound is too big for just one piece, more pieces can be added. It’s important to remember and note down how many pieces are used, so none of them get left inside the wound when the dressing is changed.
Like the closed wound, the spongy dressing for an open wound is also sealed tightly using large strips of the clear, sticky tape. A suction drain tube is then added to the dressing. This can be done in two ways, depending on the type of vacuum system being used: it can either be placed over the spongy dressing before adding the tape, or it can be fixed as part of another sticky dressing on top of the tape.
Once the dressing is completed, the NPWT device, which creates a vacuum to help heal the wound, is connected to the suction drain tube. The device will give out an electronic signal to show whether or not the treatment is working properly.
Possible Complications of Negative Pressure Wound Therapy
Negative Pressure Wound Therapy (NPWT), or vacuum-assisted wound closure, is a medical treatment used to help wounds heal. But like all medical treatments, it might have some side effects. Most common among these are pain, bleeding, potential infections, inability to remove the foam used in the treatment, and failure of the treatment due to loss of suction.
The loss of suction is mainly caused by a problem with the bandage seal covering the wound. If the seal doesn’t stick to the skin properly or falls off, the treatment might not work. This problem needs to be corrected quickly so the healing is not delayed. Other reasons for suction loss can be improper placement of the suction tube, the battery dying, blockage in the suction tube, or the suction device being full.
Further issues could include an allergic reaction to the bandage materials, more damage to the wound due to the negative pressure, or complications during the treatment like harming nearby nerves, blood vessels, or soft tissue. If the skin around the treatment area starts to break down, or if there’s pain, a skin-softening therapy or a different type of bandage can be used to reduce tension. If the wound or the edges around it start to change color, the suction should be decreased. If the problem persists or gets worse, the device should be turned off.
The treatment might also cause the patient to become dehydrated due to fluid being lost through the suction. To avoid this, fluids may need to be given through an intravenous (IV) drip.
What Else Should I Know About Negative Pressure Wound Therapy?
Negative pressure wound therapy is a helpful method used by skilled healthcare professionals to manage complicated wounds and promote healing. This technique is used in various medical specialities such as plastic surgery, orthopaedics, vascular surgery, dermatology, endocrinology, and tissue health. The type of wound you have determines how long you’ll need this therapy and how it’ll help you heal. Therefore, the duration and healing process can significantly vary for each patient. It is useful for getting the skin back to its normal, healthy state.