Understanding the Role of Plasma Bullet Currents in Heating Skin to Mitigate Risks of Thermal Damage Caused by Low-Temperature Atmospheric-Pressure Plasma Jets

Abstract

Low-temperature atmospheric-pressure plasma jets are generally considered a safe medical technology with no significant long-term side effects in clinical studies reported to date. However, there are studies emerging that show plasma jets can cause significant side effects in the form of skin burns under certain conditions. Therefore, with a view of developing safer plasma treatment approaches, in this study we have set out to provide new insights into the cause of these skin burns and how to tailor plasma treatments to mitigate these effects. We discovered that joule heating by the plasma bullet currents is responsible for creating skin burns during helium plasma jet treatment of live mice. These burns can be mitigated by treating the mice at a further distance so that the visible plasma plume does not contact the skin. Under these treatment conditions we also show that the plasma jet treatment still retains its medically beneficial property of producing reactive oxygen species in vivo. Therefore, treatment distance is an important parameter for consideration when assessing the safety of medical plasma treatments.

Characterization and Treatment Performance of an Atmospheric Pressure Plasma Jet-Operated Spinning Disc Reactor for the Treatment of Rhodamine B Dye

“…The lack of significant variation in electron density with discharge power can be attributed to the relatively constant power density of the discharge (~ 3×10 5 W/m 2 ) arising from changes in plasma area. The observed increase in gas temperature with discharge power, as shown in Figure 5b, is due to Joule's heating, which has been reported in previous studies [36][37][38][39]. Furthermore, the increase in gas temperature between 8 W and 13 W indicates that the increase in plasma area following power deposition is associated with increased OH production.…”