Nonhealing, chronic wounds (ie, wounds that have failed to proceed through an orderly and timely reparative process) present significant clinical challenges to health care professionals. In the United States, chronic wounds affect approximately 6.5 million patients (2% of the US population)1; among these, venous leg ulcers (VLUs, wounds due to chronic venous insufficiency) affect between 500 000 and 2 million people annually.2 Diabetes affects more than 29.1 million people (approximately 9.3% of the US population), and it is estimated that up to 25% of all people with diabetes will develop a diabetic foot ulcer (DFU) during their lifetime.3,4 These staggering numbers demonstrate a clinical need to provide effective treatment interventions in order to accelerate healing in chronic wounds. VLUs and DFUs represent the majority of chronic wounds treated each year in wound centers.2,4
Ultraviolet (UV) light has been used for many years as a treatment modality for chronic wounds and a variety of skin conditions. UV energy encompasses wavelengths between 180 nm and 400 nm with 3 distinct bands: UVA (400–315 nm), UVB (315–280 nm), and UVC (280–100 nm).5 Although experimental data6 from as early as 1945 suggest the positive effects of both UVA and UVB in wound healing, chronic, prolonged exposure to high-dose UVB has been linked to carcinoma formation.7,8 In contrast, UVC has been shown to be safe to use in a clinical setting,5 with evidence-based research demonstrating bactericidal effects.9
A quantitative analysis by Conner-Kerr et al9 examined the effectiveness of UVC radiation on antibiotic-resistant strains of Staphylococcus aureus and Enterococcus faecalis in vitro. Between 2 and 5 replications of each organism at 108 organisms/mL were prepared and plated on a sheep blood agar medium. Organisms on agar plates were treated with UVC (254 nm, 15.54 mW/cm2 output), resulting in a 99.9% kill rate with irradiation times of 5, 8, 15, 30, 45, and 60 seconds and a 100% percent kill rate at irradiation times of 90 and 120 seconds for a methicillin-resistant strain of S aureus (MRSA). In addition, 99.9% kill rates for vancomycin-resistant E faecalis were identified at irradiation times of 5, 8, 15, and 30 seconds.9
Thai et al10 presented a case series describing 3 individuals with chronic wounds that were locally positive for MRSA. In this study,10 UVC (using a 254-nm cold quartz UVC generator) was applied at a perpendicular distance of 1 inch from the wound base. Wounds were treated for 180 seconds; semiquantitative swab results taken before and following 7 UVC treatments showed a reduction in bacteria growth. In 2 of the cases, heavy growth of MRSA was identified before UVC treatment, and after 7 UVC treatments, light growth was noted. In the third case, light growth of MRSA was identified before UVC treatment and occasional growth (scant) of MRSA was noted after 7 UVC treatments. Two (2) of the 3 wounds were healed following 1 week of UVC treatment, and the third wound showed evidence of healing.
A prospective, 1-group, pre-post treatment study by Thai et al11 found UVC was effective in reducing bacteria in chronic wounds (pressure ulcers [PUs], VLUs, and DFUs). Participants included individuals (N = 22) with chronic ulcers exhibiting at least 2 clinical signs of infection (pain/tenderness, moderate exudate, foul odor, friable granulation tissue, slough in the wound bed, periulcer skin erythema, elevated local temperature, and swelling) and critically colonized as defined by Sibbald et al,12 as well as patients who had both a positive wound culture of at least 1 type of bacteria. These individuals received a single 180-second treatment using an UVC light lamp (wavelength = 254 nm) placed 1 inch from the wound bed. Semiquantitative swabs taken immediately before and after UVC treatment demonstrated excellent test-retest reliability of the semiquantitative swab technique used to evaluate the type and amount of bacteria present in chronic wounds (Cohen’s kappa = 0.92). A statistically significant (P <.0001) reduction in the relative amount of Pseudomonas aeruginosa, S aureus, and MRSA following a single treatment of UVC was observed. The greatest reduction in semiquantitative swab scores following UVC treatment were observed for wounds colonized with P aeruginosa and wounds colonized with only 1 species of bacteria. Significant (P <.05) reductions in the relative amount of bacteria also were observed in 12 ulcers in which MRSA was present, but the effects of UVC were not as robust for MRSA (only 1 level reduction) after the standard 180-second treatment time. These data indicate multiple treatments of UVC for 180 seconds may be required to eradicate organisms that are sensitive to antibiotics.
Although evidence is strong for the bactericidal effects of UVC in chronic wounds in vitro, clinical studies examining the effects of UVC, specifically the effect on wound healing, are limited. In a 1995 review, Kloth13summarized modalities that have been shown to have a positive effect on nonhealing, slowly healing, or regressing wounds as well as the effects of UVC on wound healing including hyperplasia, reepithelialization or desquamation of the leading edge of periulcer epidermal cells, granulation tissue formation, and sloughing of necrotic tissue. The literature review by Rennekampff et al14 noted UVC also may stimulate and restore normal melanocyte numbers and distribution in reepithelialized wounds while preventing hypopigmentation. However, few studies have examined the healing response on chronic wounds of various etiologies treated with UVC. The purpose of this retrospective, descriptive study was to evaluate the outcomes of UVC as an adjunct modality when used with standard care for chronic wounds.