The PlasmaDerm\u00aeFLEX (CINOGY Systems GmbH, Duderstadt, Germany) was used throughout this study. This direct plasma source utilizes the skin tissue as counter electrode, whereas CAP formation occurs in the ambient air layer above the tissue at a rate of 300 Hz. The manufacturer declares that the device with an electrode area of 27.5 cm^2 is a medical device class IIa. The electrode is equipped with nubs, which are to be brought in contact with the counter electrode (human skin) for intended use. The nubs serve as spacers and ensure a constant distance of 2 mm between the counter electrode and the surface of the dielectric material housing the high voltage electrode. In this work, the PlasmaDerm\u00aeFLEX was operated at a power density of 4 mW/cm^2 facilitating gas temperatures of 30 \u00b0C \u2013 40 \u00b0C and electron energies of 8 \u2013 12 eV.
\nfrom: Thomas Borchardt et al 2024 J. Phys. D: Appl. Phys. 57 385203.
\n", "procedure": "Especially for this study, we have developed experimental measures to realize three CAP modalities with different characteristics when applied to the subjects.
\nStandard CAP treatment:
\nThe CAP source was positioned and operated on the skin tissue as recommended by the manufacturer. Consequently, the full spectrum of plasma components was able to interact with the skin tissue when applied to the treatment area.
CAP treatment at no electric currents or fields:
\nA fine mesh made from a conductive metal alloy (Aaronia Shield ULTRA, Aaronia AG, Strickscheid, Germany) was placed between the CAP electrode and the skin and connected to ground potential. As a consequence, the skin tissue no longer acts as a counter electrode, thus eventually avoiding formation of electric fields in the tissue and electric current flow into the body. Gaseous species, however, were still able to interact with the tissue by diffusing through the mesh. UV\u2013VIS radiation, however, was partly shielded by the mesh and the intensity on the skin surface was reduced by approx. 50% compared to standard treatment as estimated from the transmission factor defined by the geometrical properties of the conductive mesh.
CAP treatment at reduced RONS concentration:
\nThe CAP electrode was placed on the treatment area (TA) just like in standard configuration but the electrode was embedded in a selfconstructed hood thus creating a cavity above the subject\u2019s skin in the TA. The hood exhibits a slight curvature on the plane in contact with the participant\u2019s arm in order to support a tight connection. The contact surfaces with the skin were equipped with silicone thus realizing a gas-tight connection and a cavity directly above the skin surface in the TA. The plasma electrode is placed in this cavity so that the nubs are in direct contact with the skin. At the top, the hood provided an inlet and an outlet to realize the gas flow as depicted. Compressed air at a temperature of 295 K and relative humidity of 50% was streamed through the hood at a volume flow rate of V\u02d9 in = 5 l/min when attached to the skin thus eventually reducing local concentrations of RONS on the skin surface compared to standard treatment but also skin temperature as a result of convective cooling. From the cross section of the cavity beneath the hood and the volume flow rate we estimate a flow velocity at the skin surface of approx. 1 m/s. For these conditions, a single gas molecule is transported by 0.1 \u03bcm in the flow direction during the typical lifetime of a microdischarge of approx. 100 ns. In view of the typical microdischarge diameters of approx. 200 \u03bcm and drift velocities in the order of 10^5 m/s, we consider the impact of the hood in combination with the artificial gas stream on physical CAP components such as UV\u2013VIS radiation, electric currents, or electric fields to be negligible.
from: Thomas Borchardt et al 2024 J. Phys. D: Appl. Phys. 57 385203.
\n" }, "medium": { "name": "ambient air, compressed air, air", "properties": "Standard and noCurrent: ambient air, 0 l/min; lessRONS: compressed air, 5 l/min
\n", "procedure": "Compressed air was humidified to approx. 50% relative humidity
\n" }, "target": { "name": "healthy skin, intact skin, skin", "properties": "The field of examination was the lateral, proximal upper left arm of 10 healthy subjects with no visible signs of skin injuries or skin inflammation in the treatment area and no morbidities such as cardiac dysfunction, chronic liver or kidney disease, diabetes mellitus or vascular disease and no oral or skin therapy of the field of examination; three women, seven men, mean age: 27.2 \u00b1 4.52 years, mean BMI: 23.9 \u00b1 3.04.\r\n\r\n---\r\nfrom: Thomas Borchardt et al 2024 J. Phys. D: Appl. Phys. 57 385203.", "procedure": "To stabilize the subject\u2019s microcirculation prior to data assessment, all participants were asked to lie down on a mattress and rest for at least ten minutes. To prevent subjects from falling asleep associated with a drop in microcirculation parameters during the lengthy experiments, their level of attention was stabilized by showing familiar movies.\r\n\r\n---\r\nfrom: Thomas Borchardt et al 2024 J. Phys. D: Appl. Phys. 57 385203." }, "diagnostics": { "name": "TIVITA Tissue system", "properties": "Hyperspectral imaging at a range of 500 \u2013 1000 nm, spectral resolution of approximately 5 nm, resolution of 640 \u00d7 480 pixels
\n", "procedure": "The camera system was positioned 0.5 m above the treatment area, as recommended by the manufacturer for correct data acquisition. After the first ten minutes of resting, a microcirculation baseline was recorded for a period of ten minutes with one picture of the TA taken every 2 min (Baseline = 6 datasets). Afterwards, CAP application was performed with either one of the CAP modalities on all participants for 4.5 min in separate experiments (CAP treatment = 2 datasets missing), with at least one week between experiments on the same subject. Immediately after the intervention, microcirculation parameters were assessed for 30 min at a rate of one picture recorded every 2 min (post treatment = 16 datasets).
\nAssessment of microcirculation parameters
\nThe assessment of microcirculation parameters was performed by hyperspectral imaging (TIVITA\u00ae Tissue System, Diaspective Vision GmbH, Salzhaff, Germany). This is a medical device (class I) camera system that displays tissue parameters such as near infrared perfusion index (NIR) representing information from deeper tissue layers (3\u20135 mm), tissue hemoglobin index (THI) describing total hemoglobin concentration, tissue oxygen saturation (StO2) describing hemoglobin\u2019s oxygen saturation and tissue water index (TWI). The method is based on the scattering of electromagnetic radiation with blood components in the wavelength range of 500\u20131000 nm.
Processing of image data
\nIn order to evaluate the impact of the interventions, microcirculation parameters within the TA were investigated, therefore, the TA was divided into an untreated reference area (REF) and a treated region of interest (ROI), and both were compared. The analysis software (TIVITA\u00ae Tissue System, Diaspective Vision GmbH, Salzhaff, Germany) of the camera provides the opportunity to set individual markers of round shape and variable size for every image set. Two markers represent the treated tissue (ROI), while two other markers represent the reference area (REF).
from: Thomas Borchardt et al 2024 J. Phys. D: Appl. Phys. 57 385203.
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