Impact of the electrode–tissue contact area on physical process parameters of a dielectric barrier discharge plasma source for wound treatment

Abstract This study examines the operational safety of wound treatment accessories based on direct cold atmospheric plasma (CAP) in scenarios where unintended incomplete physical contact between the high-voltage electrode and biological tissue occurs during treatment. By mimicking incomplete contact using two experimental approaches, we systematically varied the effective electrode area and assessed key physical process parameters: electrical input power, patient leakage currents, surface temperature increase, UV radiation emission, and the emission rates of selected reactive oxygen and nitrogen species (RONS). Measurements were taken in accordance with DIN SPEC 91315 and relevant IEC standards, using metal meshes and tissue models, such as pig ears and hydrogels, as counter electrodes. Experimental trends reveal increasing leakage current densities as electrode area is reduced. Absolute values for leakage currents remain consistently below established safety thresholds. As a result, CAP exposure causes a slight yet physiologically harmless heating effect (ΔT < 2.5 K). A comparable trend was observed for UV intensity, with spectrally weighted irradiances remaining at least 40-fold below risk-related limits. RONS analysis identified ozone as the predominant species, with only slight increases in emission rates during partial electrode ignition. The predictions for the expected average ozone concentrations during typical operating times of the devices indoors generally comply with air quality guidelines. In conclusion, partial electrode contact does not compromise the key safety parameters of wound treatment accessories based on direct CAP technology. These findings support the safe use of such devices under variable clinical conditions and inform future optimization efforts, highlighting the need to further integrate efficacy and safety evaluations in translational plasma medicine.