Therapeutic current estimation and leakage current safety of a cold air plasma jet on chronic wounds

Abstract

Abstract Cold atmospheric air plasma jets (CAAPJs) are increasingly recognised for their efficacy in chronic wound treatment, with reactive oxygen and nitrogen species (RONS) traditionally cited as the primary therapeutic mechanism. However, their electromagnetic nature inevitably involves electrical interactions with wound tissue that have not yet been explicitly quantified. This work presents a quantitative framework distinguishing two coexisting electrical phenomena during CAAPJ treatment. First, the oscillating field at 30 kHz induces ionic currents in microscopic closed loops on the wound surface. Applying Ohm’s law with the measured electric field ( $$E \approx 10$$  V/mm) and wound exudate conductivity ( $$\sigma = 0.5$$  S/m), an induced current of 2–20 mA is obtained depending on exudate layer thickness, spanning and exceeding the therapeutic range of established Wound Healing Electrostimulation Devices (WHESDs). Second, the systemic patient leakage current — defined by IEC 60601-1 for Type B applied parts (limit: 100  $$\mu$$ A) — was measured under worst-case conditions using a brass target at zero resistance to earth, yielding values below 100 nA, more than three orders of magnitude below the normative limit. These results suggest that the long-standing RONS-versus-electric-field discussion in plasma medicine may be more productively framed as a question of complementary contributions: the therapeutic relevance of CAAPJs may lie in the co-delivery of both chemical and electrical mechanisms, while the device simultaneously guarantees full electrical safety. The two-current framework also provides a rigorous physical basis for the regulatory assessment of CAAPJ devices under IEC 60601-1.