Description

End-stage peripheral arterial disease (PAD) is characterized by critical limb ischemia, which manifests clinically as insufficient arterial perfusion leading to ischemic rest pain, ulceration, and gangrene. A substantial proportion of these cases occur in patients with diabetes complicated by lower extremity arterial occlusion. Ischemia in diabetic patients predominantly affects infrapopliteal arteries, often presenting bilaterally and symmetrically, with diffuse lesions that commonly involve the entire vessel wall. These patients are more prone to both intimal atherosclerosis and medial arterial calcification.

A large multicenter cohort study in China that enrolled 669 patients with diabetic foot ulcers from 15 tertiary hospitals reported that more than 98% had underlying neurovascular pathology. The overall amputation rate was 19.03%, with major and minor amputation rates of 2.14% and 16.88%, respectively. Notably, the five-year survival rate after amputation was approximately 50%, which is lower than that observed for many malignancies. According to a large European cohort study, about half of diabetic foot ulcers are attributable to neuropathic or ischemic etiologies. Both macrovascular and microvascular dysfunctions jointly impair tissue perfusion and exacerbate diabetic foot pathology. From a clinical perspective, successful arterial revascularization alone is not sufficient; maintenance and optimization of distal microcirculatory perfusion following revascularization are also essential for effective ulcer healing.

With advances in endovascular techniques, infrapopliteal angioplasty has become the first-line treatment for diabetic lower limb ischemia, with proven efficacy. However, even after successful revascularization, some patients continue to suffer from inadequate distal perfusion due to microembolization or from persistent, hard-to-heal ulcers driven by the underlying pathophysiology of diabetic wounds. Several studies have demonstrated that diabetic patients experience metabolic dysregulation, local wound hyperglycemia, and accumulation of advanced glycation end-products (AGEs); combined with immune dysfunction and chronic inflammation, these factors maintain wounds in a persistent inflammatory state. Chronic inflammation suppresses vascular endothelial growth factor (VEGF) and angiopoietin-1 (ANG-1) expression, impairs endothelial cell function, and leads to angiogenesis disorders and delayed tissue repair. Reduced VEGF and ANG-1 expression has been confirmed in skin specimens from diabetic patients. In addition, peripheral neuropathy further inhibits neovascularization.

Despite widespread clinical use of advanced wound dressings-such as hydrogels, natural or synthetic polymer-based products, and other dressings designed specifically for diabetic ulcers-treatment efficacy remains limited, and costs can be substantial. For patients with diabetic foot ulcers complicated by large-vessel occlusion, ongoing assessment and support of distal microvascular perfusion remain a major unmet clinical need, even after successful revascularization.

Cold atmospheric plasma (CAP) has been widely adopted in medical applications and has demonstrated robust antimicrobial activity as well as the capacity to enhance tissue microcirculation and promote wound healing, with excellent patient tolerance. Multiple preclinical and clinical studies have confirmed the bactericidal efficacy of CAP, including activity against multidrug-resistant organisms. For example, Brun et al. reported that CAP effectively eradicates Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) in vitro, achieving results comparable to antibiotics but with higher efficiency. Lis et al. found that CAP could also inactivate MRSA, Klebsiella pneumoniae, and Acinetobacter baumannii. Korean researchers Kim et al. demonstrated that CAP effectively disrupts biofilms formed by P. aeruginosa and other pathogens in canine skin and ear infections. In a prospective clinical study, Stratmann et al. showed that CAP treatment accelerates wound healing in diabetic foot ulcers. Boekema et al. \[6\] reported a significant reduction in bacterial load and no serious adverse events in patients with P. aeruginosa infections treated with CAP, confirming its safety profile.

The antimicrobial mechanism of CAP is primarily attributed to the generation of reactive oxygen and nitrogen species (RONS), which induce local free radical formation and disrupt microbial membranes, leading to apoptosis without fostering antimicrobial resistance. This highlights CAP as a valuable adjunct to conventional antibiotic therapy, especially for wounds infected with multidrug-resistant bacteria.

Importantly, CAP's benefits extend beyond antimicrobial effects. Numerous studies indicate that CAP promotes wound healing not only by eliminating pathogens but also by directly activating tissue regeneration. At the cellular level, CAP has been shown to modulate fibroblasts, vascular endothelial cells, and keratinocytes. Stratmann et al. observed that CAP enhanced tissue regeneration in diabetic foot ulcers without a corresponding decrease in colony-forming units, suggesting a regeneration mechanism independent of bactericidal action. In the study by Brehmer et al., CAP (PlasmaDerm device) significantly improved healing rates in lower extremity venous ulcers compared with standard care. These findings imply that CAP can accelerate tissue regeneration and shorten healing time, regardless of its antimicrobial effects.

Delayed wound healing is often accompanied by local microcirculatory disorders, resulting in decreased collagen production and impaired proliferation and migration of keratinocytes and fibroblasts. Several clinical trials have demonstrated that CAP exposure at therapeutic doses increases local skin blood flow and tissue oxygen saturation without raising skin temperature. The underlying mechanism may involve nitric oxide (NO) permeation, modulation of cysteine disulfide bonds and acidic lipid groups, reduced local pH, and improved microcirculation. In animal and cellular experiments, Arndt et al. demonstrated that CAP induces oxidative stress pathways in a paracrine and autocrine manner, stimulating keratinocytes, fibroblasts, and endothelial cells to produce vascular growth factors (EGF, FGF-2, IL-8, uPA, angiopoietin, VEGF), thereby promoting angiogenesis.

Based on these findings, this study aims to evaluate the efficacy and safety of CAP combined with endovascular intervention in patients with diabetic foot ulcers complicated by lower extremity arterial occlusion, providing essential evidence to support future large-scale clinical application of CAP.