# Cold Atmospheric Pressure Plasma in Wound Healing and Cancer Treatment
## 2 CAP Treatment to Promote Healing of Acute and Chronic Wounds  
A couple of smaller studies and case reports assessed the safety and efficacy of cold atmospheric pressure plasma (CAP) to treat acute and chronic wounds (Table 1). The first studies primarily aimed at showing the safety of different CAP devices and a reduction of bacterial load in chronic wounds [6, 7, 8, 9]. For example, two prospective randomized and controlled studies assessing the use of a plasma jet (MicroPlaSter, the predecessor of SteriPlas, Adtec Healthcare; Adtec Plasma Technology Co. Ltd., Hiroshima, Japan/London, U.K.), including 36 and 24 patients with chronic wounds, respectively, showed a significant reduction of the bacterial load [6,7]. A case-control study comparing the efficacy of another plasma jet device (kINPen MED, neoplas tools GmbH, Greifswald, Germany) with ocenidine dihydrochloride (ocenidine) treatment revealed a similar anti-bacterial effect in the CAP group compared to the ocenidine group [9]. A similar study of the same 34 patients showed advantages regarding the antimicrobial efficacy of sequential treatment with CAP and Ocenidine _versus_ mono-treatment of just one of the two antiseptic treatments [8]. While the primary endpoint of these studies was safety and bacterial load, a retrospective follow-up study of the two studies by [PERSON] and colleagues [6,7] revealed that CAP might accelerate the healing of chronic wounds [10]. A first monocentric two-armed, open, prospective, randomized, and controlled pilot-study regarding CAP treatment of chronic leg venous ulcers used a dielectric barrier discharge plasma source (PlasmaDerm VU-2010, Cinogy GmbH, Duderstadt, Germany) and included 14 patients [11]. Half of the patients received standard wound care, and the other half received CAP treatment in addition to standard wound care. In both groups, a reduction of wound size by about 50% was observed, whereas, after three weeks, a faster and stronger reduction of wound size was observed in the CAP treated group. One patient in the CAP treated group experienced complete healing. In the so far discussed studies, wound healing was examined either as a secondary endpoint or retrospectively. A comprehensive prospective, randomized, controlled trial comprising 50 patients, however, specifically assessed wound size reduction of pressure-induced ulcers after CAP treatment (BIOPlasma jet, PhotoBioCare, Nonthaburi, Thailand) and revealed a significantly accelerated wound size reduction in the CAP treated group [12]. Besides investigating the effect of CAP on chronic wounds, studies have also been conducted to assess the effects of CAP on acute wounds. In a series of case-reports, four sterile laser skin lesions were induced in five volunteers [13]. These acute wounds were treated for either 10 s, three times 10 s, 30 s with CAP (kINPen MED, neoplasms tools GmbH, Greifswald, Germany), or left untreated. Treatment for three times 10 s and one time 30 s showed the best outcome for early wound healing, as well as 6 and 12 months after treatment [14]. A significantly improved healing of vacuum-generated acute wounds was observed after CAP treatment (kINPen, neoplasms tools GmbH, Greifswald, Germany) in comparison with either no treatment, ocenidine treatment, or sequential CAP and ocenidine treatment [15]. Significantly improved wound healing was also observed after CAP treatment (MicroPlaSter \(\beta\), Adtec Plasma Technology Co. Ltd., Hiroshima, Japan/London, U.K.) compared to placebo in a study assessing the effect of CAP on skin graft donor sites [16]. Half of the skin graft donor wounds were randomly treated CAP, and the other half received placebo treatment. The healing of the wounds was assessed in a blinded fashion by independent experts. Despite these multiple indications for a positive influence of CAP on wound healing, a meta-analysis published 2019 came to the conclusion that CAP treatment based on the included studies has no significant effect on wound healing over standard care [17].