Digital editor, Monet Bailey, examines the burden of chronic wounds on quality of life and the latest innovations in wound care treatment.
A chronic wound develops when any acute wound fails to heal in the recommended time frame, typically within three months. If a wound fails to heal, it could be due to a lack of one or more of the main requirements of healing, including a healthy supply of blood, oxygen and nutrients, and a clean and infection-free environment. Wounds, which are under constant pressure like weight-bearing conditions, can cause a cumulative breakdown of the tissue.
Understanding chronic wounds and their risk factors
Chronic wounds are common with an estimated 1 to 2% of the population in developed countries experiencing a chronic wound during their lifetime. Types of chronic wounds can include:
- Infectious wounds: this could be a bacterial, fungal or viral infection which without the proper treatment, can lead to the wound not healing in the correct time frame;
- Ischemic wounds: the wound is not receiving sufficient bloody supply and this can delay or prevent the healing process;
- Radiation poisoning wounds: excessive exposure to therapeutic (gamma rays or X-rays) or accidental (exposure to radioactive materials from nuclear plant accidents or radioactive devices that detonate) can weaken the immune system and delay healing; and
- Surgical wounds: wounds caused by incisions made during surgery can become chronic if blood supply to the area was damaged.
Ulcers are the most common type of chronic wound and can occur as a result of a medical condition these include:
- Arterial ulcers: these can occur from hypertension, artherosclerosis (plugging) and thrombosis (clotting), where the reduced blood supply leads to an ischemic state;
- Venous ulcers: these account for more than half of ulcer cases, mainly found in the lower limbs and are associated with deep vein thrombosis, varicose veins and venous hypertension. These ulcers can lead to stasis, where the blood fails to circulate normally;
- Diabetic ulcers: in uncontrolled diabetes mellitus, these ulcers occur resulting in impaired immune function, ischemia and neuropathy; and
- Pressure ulcers: the pressure and friction from bodyweight for a prolonged duration can lead to ulceration (bed sores); especially on the back and on the ankles and feet.
Individuals who have an acute wound are at risk of it becoming chronic however, some people are more at risk than others. People with specific conditions or those following certain lifestyles can be more vulnerable to chronic wounds, such as:
- Chronic medical conditions, like diabetes, high cholesterol, severe burns, cancer or AIDS;
- Vascular disease, including heart disease, hypertension, atherosclerosis, anemia, varicose veins or deep venous thrombosis;
- Elderly, immobile or obese people;
- Unhealthy lifestyles or habits like smoking, poor diet and hygiene or lack of exercise;
- Previous history of ulcers, multiple surgeries or prolonged periods of bed rest;
- Weak immune system, as in patients taking corticosteriods, chemotherapy or radiotherapy; and
- High-risk occupation with radiation exposure or long periods of sitting.
Preventing chronic wounds
Taking appropriate preventative measures can decrease the chances of wound chronicity and serious complications developing.
Offloading excessive pressure
Pressure ulcers account for around 43% of chronic wounds. Avoiding excessive pressure on any body parts for an extended period is essential to prevent pressure ulcers. Techniques such as changing seated positions regularly, avoiding crossing the legs and regularly exercising to improve circulation can improve this condition.
Diabetic foot ulcers can be prevented by ensuring proper footwear is worn, not going barefoot and through routine checks of the feet and legs. However, if an individual is immobile, repositioning throughout the day, around every two hours, can help offset the pressure.
Optimising nutrition and promoting healthy eating
The body should be fuelled with vitamins, minerals, and nutrients to aid the prevention of chronic wounds. Whilst, supplementing these nutrients can be beneficial, focusing more on eating whole, unprocessed foods and lean protein promotes a healthier lifestyle.
Eating healthy food can help reduce the Body Mass Index (BMI) and managing blood sugar levels in individuals with diabetes is necessary to avoid chronic wounds.
Quitting smoking will aid chronic wound prevention as this habit can significantly decrease your body’s natural healing process.
Appropriate moisture levels
Wounds require a certain level of moisture to heal correctly as dry environments lead to cracking, dehydration, and delayed healing. However, too much moisture can increase bacteria spreading, which increases the risk of infection. By utilising efficient wound dressings, appropriate moisture levels will be retained.
Maintain standard treatments
An important technique to avoid chronic wounds is treating the site of infection correctly and in a timely manner. Standardised treatment plans for specific injuries should be implemented which can include debridement, negative pressure wound therapy and hyperbaric oxygen treatment.
What are the current treatment options?
As standard, the wound will be cleaned with a saline solution, however it is unclear how effective various cleaning solutions are for cleaning the wound and the effect on the healing process. The chronic wound will be covered in a dressing, such as, films, gauze, or hydrocolloid dressings with the aim to remove excess fluid and protect it from infection. It is recommended that dressings are changed regularly once they cannot soak up anymore wound secretions, they slip out of place, or if fluid leaks out the bandage.
Doctors or nurses often remove dead or inflamed tissues from chronic wounds, using instruments like tweezers or a scalpel. This is known as debridement. It can be a painful process; therefore, a local anaesthetic is used to numb the wound beforehand. Pain killers can also be taken if the pain is severe.
Another form of debridement involves the use of a species of maggots (fly larvae) that are specifically bred for medical purposes. The maggots are placed on the wound, as they are or in a pouch. They remove dead tissue and fluid from the wound.
An enzyme-based gel is sometimes applied to help clean the wound.
There is not enough good research on the advantages and disadvantages of the various debridement techniques to be able to say how effective they are.
Compression stockings and bandages
If poor blood circulation caused the chronic wound, then compression stockings or compression bandages can support the healing process. The pressure from the stockings and bandages helps the veins to carry the blood back to the heart and improves circulation.
If a wound is infected with bacteria, it is less likely to heal. Antibiotics may be considered dependant on how severe the infection is. They can be applied using an ointment or placed on the wound using a compress. The initial study results show that wounds in people with diabetic foot syndrome heal faster as a result. On the other hand, it is not clear whether this also applies to wounds caused by other underlying diseases.
Hyperbaric oxygen therapy
With hyperbaric oxygen therapy, the individual will breathe in oxygen under high pressure in a special chamber. This is meant to increase the oxygen concentration in their blood and improve blood supply to the wound.
Ultrasound and electromagnetic therapy
Ultrasound therapy involves treating chronic wounds using sound waves. The sound waves make the tissue warmer, but this type of therapy has not been proven to help healing. Electromagnetic therapy uses weak electromagnetic waves applied to the wound using pillows or mats that have magnets in them.
Negative pressure wound therapy
Negative pressure wound therapy works by covering the chronic wound in an airtight dressing that is connected to a pump by a thin tube.
The pump sucks fluid out of the wound, creating negative pressure across the wound’s surface. The aim of this treatment is to increase the flow of blood to the wound whilst keeping it moist. The pump system is used at regular intervals or continuously. However, there is a lack of evidence that negative pressure wound therapy can help chronic wounds.
Skin grafts are only considered as a treatment option where a wound is so large it cannot close on its own. The procedure involves taking skin from another area of the body, typically the thigh, and transplanted on the wound.
Studies have showed that these increase the chances of poorly healing venous leg ulcers closing faster. Foot wounds also healed faster after a skin graft than after standard treatment.
The future of care
The market for chronic wound technology is growing at a rapid pace, with research teams from around the world working towards new, innovative approaches to caring for wounds.
Printing skin equivalents
Research teams from the University of Birmingham and the University of Huddersfield have developed a new innovative approach to print skin equivalents that has the potential to change the landscape of what is currently achievable in wound healing.
The novel technique is the first of its kind to simulate three layers of skin, the hypodermis, the dermis, and the epidermis. The team utilised a method called suspended layer additive manufacturing (SLAM), this enabled them to create a gel-like material to support the skin equivalent. By altering the structure of the gel, it produces produce a bed of particles that can then support the second phase of gel injection.
During the printing, the skin layers are deposited within the support gel that holds everything in place; after the printing, the team washed the support material away, leaving only the layered skin equivalent behind.
Natural killer cells
New research led by the University of Zurich has found that natural killer cells help with the management of wounds. After tissue injury, an adequate immune and repair response are prerequisites for rapid wound closure and the prevention of microbial infections.
A skin injury triggers skin repair and defence mechanisms including inflammation and regenerative angiogenesis, and these must be tightly coordinated. Innate lymphoid cells (ILCs) are an early source of cytokines, particularly NKp46+ group 1 ILCs (ILC1s) that comprise natural killer (NK) cells, guide inflammation, and tailor the immune response to the type of the encountered insult. While the role of skin-resident ILC1s for steady-state skin homeostasis is increasingly recognised, the significance of infiltrating NK cells for skin repair and antimicrobial defence remains unknown.
NK cells directly kill tumour cells and microbes, and secrete cytokines, including Interferon y (IFN-γ), Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF), and Tumour Necrosis Factor α (TNF) to instruct immune responses as well as repair processes. IFN-γ and GM-CSF drive macrophage activation and favour proinflammatory M1 over a pro-regenerative M2 polarisation. In addition, IFN-γ has been shown to exert anti-angiogenic effects. Hypoxia is a characteristic feature of the tissue microenvironment during skin repair and bacterial infections, with tissue oxygen tensions lower than 10mmHg in wounds and necrotic tissue foci.
Wound-infiltrating NK cells need to function under such conditions and adapt to low oxygen, which is mediated by hypoxia-inducible transcription factors (HIFs), with HIF-1 and HIF-2 being the most extensively studied isoforms. HIFs are basic-helix-loop-helix transcription factors that consist of a constitutively expressed β-subunit and an oxygen-regulated α-subunit that is hydroxylated by prolyl hydroxylases in the presence of oxygen, and subsequently degraded through the ubiquitin proteasome pathway via interaction with its negative regulator von Hippel-Lindau (VHL) protein. The role of HIFs in tumour-infiltrating NK cells is controversial but in general, evidence shows that HIFs are important for NK cell performance in low oxygen environments. Yet, the impact of the hypoxic response in NK cells upon skin injury and infection remains enigmatic.
The study found that mice lacking the Hypoxia-inducible factor HIF)-1α isoform in NK cells show impaired release of the cytokines Interferon (IFN)-γ and Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) along with a blunted immune response. This accelerates skin angiogenesis and wound healing. Despite rapid wound closure, bactericidal activity, and the ability to restrict systemic bacterial infection are impaired. Conversely, forced activation of the HIF pathway supports cytokine release and NK cell-mediated antibacterial defence including direct killing of bacteria by NK cells, despite a delayed wound closure. Their results identify HIF-1α in NK cells as a nexus that balances early antimicrobial defence versus a global repair in the skin.
- What are the treatment options for chronic wounds? – InformedHealth.org – NCBI Bookshelf (nih.gov)
- UK scientists develop cutting-edge wound healing technique (healtheuropa.com)
- Exploring how natural killer cells can enhance wound healing (healtheuropa.com)
This article is from issue 20 of Health Europa Quarterly. Click here to get your free subscription today.