ConvaVAC™ Ag+ Negative Pressure Wound Therapy System in Chronic Wounds

Chronic wounds, also sometimes referred to as hard-to-heal wounds, are defined as wounds that do not transition through the normal phases of healing in a timely manner. These wounds reduce health-related quality-of-life (QoL) for the patient and pose a substantial burden on healthcare professionals (HCPs) and healthcare systems. The number of chronic wounds is rising. With a global prevalence of ~1.9 per 1,000 and 1-2% in developed countries, it is predicted that the incidence of chronic wounds will increase with the aging population. Wound care accounts for 2-4% of healthcare expenditure in Europe and costs $28 billion per year in the United States.

A significant contributing factor to the delayed healing of chronic wounds is the increased risk of infection. Evidence suggests that biofilm comprises at least 78% of chronic wounds. Biofilm is communities of microorganisms embedded in a matrix of extracellular polymeric substances. This matrix protects microorganisms from antibiotics, antiseptics and the host immune response. The development of biofilm in wounds elicits a sub-optimal host inflammatory response, and is a precursor of local infection. The presence of biofilm-forming microorganisms leads to a four-fold higher chance of infection in chronic wounds compared with non-biofilm forming microorganisms (p=0.0001). The presence of biofilm in wounds can also lead to the failure of antibiotics.

Silver ions kill micro-organisms rapidly by blocking enzyme activity associated with respiration, impairing DNA synthesis and affecting cell structure. Silver is also thought to reduce bacterial adhesion and destabilize biofilm as well as increase susceptibility of bacteria to antibiotics. In recent years, a wide range of wound dressings containing elemental silver or silver releasing compounds have been developed and have gained considerable popularity. Silver dressings reduce wound healing times, hospital stays, dressing change frequency, the requirement for analgesia and reduce the number of MRSA-infected wounds. Several systematic literature reviews have been conducted highlighting the positive effects of using silver dressings on chronic wounds One of the most prevalent chronic wounds is venous leg ulcers (VLUs). Chronic leg ulcers affect around 1% (increasing to 4% in elderly populations) of the population, VLUs account for up to 90% of all chronic leg ulcers. Standard treatment of VLUs includes local wound management (e.g. debridement, moist dressings), compression therapy and topical antimicrobials. Despite standard treatment, VLUs are often associated with pain, reduced mobility, an increased risk of infection and extensive healing times. Such effects ultimately contribute to a reduced patient QoL. Only about half of VLUs heal within 4 months and recurrence rate is as high as 57% within the first year. This leaves a significant proportion of non-healing ulcers which place a burden on heath resources and patient QoL. Improvements in healing of VLUs would have a significant impact.

A promising preventative intervention is Negative Pressure Wound Therapy (NPWT), first described in the 1990's NPWT was originally designed for the treatment of open wounds. NPWT consists of a closed sealed system, the wound is covered with a foam or gauze dressing and sealed with an occlusive film. Intermittent or continuous sub-atmospheric pressure is created by a vacuum pump which draws excess fluid from the wound and collects it in a connected waste liquid collector. The system promotes granulation tissue formation, increases tissue blood flow, increases lymphatic clearance and removes bacteria from the wound bed. It therefore has the potential to improve wound outcomes rather than just manage the symptoms. NPWT has been found to be an effective treatment to heal chronic, complex and infected wounds. Recently, NPWT has been recommended in the management of chronic wounds including VLUs.