Comparison of two skin temperature assessment methods after the application of topical revulsive products: Conductive iButton data logger system vs contact-free infrared thermometry.

BACKGROUND: Skin temperature assessments comprise conductive and contact-free techniques. Comparison between conductive data loggers and contact-free thermometry after the application of revulsive products is scarce. This study aimed to compare iButton data loggers with an infrared thermometer after the application of two revulsive products. Secondly, the relation between skin temperature kinetics with skin's perfusion of microcirculation was investigated. MATERIALS AND METHODS: Healthy females (n = 25) were randomly allocated to two groups, representing the products A and B. Skin temperature was measured with "iButtons" and an infrared pistol at baseline and up to 1 hour after application. Skin's perfusion of microcirculation was monitored with a laser speckle contrast imager. RESULTS: Baseline "iButton" temperature values were significantly lower compared with infrared pistol values in both groups. After application of the products, skin temperature decreased as recorded with both devices followed by an increase to baseline values when measured with the pistol. The results obtained by the "iButtons" reached values above baseline in both products towards the end of the follow-up period. A moderate correlation was found between infrared pistol and "iButton" system in product A, with a weak negative correlation between skin's perfusion of microcirculation and temperature devices. For product B, the correlation between the devices was moderate and between skin's perfusion and temperature devices weak and positive. CONCLUSION: Both devices produced similar kinetics, except at baseline, where they may differ as metallic loggers have been insufficiently adapted to skin temperature. Skin's perfusion of microcirculation could not explain skin temperature changes.

Hydration measurements of the stratum corneum: comparison between the capacitance method (digital version of the Corneometer CM 825®) and the impedance method (Skicon-200EX®).

BACKGROUND: Measurement of stratum corneum (SC) hydration often involves the use of commercial instruments. The aim of this study was to compare and validate two recent instruments: the Corneometer 825® (digital probe) and the Skicon-200 EX®. METHODS: In vitro calibration was carried out on filter pads using different solvents, measurements over different layers of plastic foils, and evaluation of desorption kinetics. In vivo measurements were carried out on skin sites covering a range of very dry to well-hydrated skin areas. RESULTS: Conductance measurements are influenced by electrolytes while capacitance measurements are not. Dielectric constant of the solvents influences the values of both instruments (r respectively 0.92 and 0.99). The capacitance method carries information from deeper layers (up to 45 µm) compared with the conductance instrument (up to 15 µm). Desorption experiments show a strong relation between the amount of water and respectively the capacitance and the conductance values. The in vivo experiments revealed a strong relation between the two methods (r = 0.97). Sensitivity of the capacitance method is limited for the highest hydration values. CONCLUSIONS: Both instruments allow a certain calibration and both give good estimates of the SC hydration.

Influence of probe application pressure on in vitro and in vivo capacitance (Corneometer CM 825(®)) and conductance (Skicon 200 EX(®)) measurements.

BACKGROUND/PURPOSE: The measuring probe of the electrical hydration instruments is equipped with a spring system to ensure a constant pressure of probe application on the skin surface. However, it is possible to trigger the measurement at, respectively, a low and a high force of probe application. It is the purpose of this paper to compare the in vitro and in vivo hydration values of the capacitance and conductance method at, respectively, low and high values of application pressure on the considered surface. METHODS: In vitro capacitance and conductance hydration measurements were carried out at a low and a high pressure on a calibration filter pad impregnated with different alcohols and in vivo on different skin sites covering a wide range of hydration values. RESULTS: The in vitro results were pressure dependent and higher hydration values were noticed when the probes were applied with a high pressure compared with a low pressure. In vivo, the pressure effect was a function of the skin type and it was more pronounced for dry skin (40%), lower for normal skin (20%) and the lowest for hydrated skin (5-8%). CONCLUSION: This study confirms the influence of probe pressure application on the skin surface when carrying out capacitance and conductance hydration measurements.

Determination of the in vivo bioavailability of iontophoretically delivered diclofenac using a methyl nicotinate skin inflammation assay.

BACKGROUND/AIMS: In this study, we investigated the bioavailability of iontophoretically delivered diclofenac with the methylnicotinate (MN) test. The inhibition of an erythema provoked by MN is proportional to the bioavailability of diclofenac in the skin. It was our aim to use this procedure in the determination of the contribution of, respectively, passive diffusion, occlusion and electrically assisted delivery during an iontophoretic procedure as used in physiotherapy. METHOD: A total of six application sites were marked on the volar forearms of each volunteer (n=12), for the following treatment and/or control modes: A=cathodal iontophoresis of 12 mg/cm(2) Voltaren Emulgel (diethylammonii diclofenac 1%) for 20 min; B=passive diffusion under a contact sponge; C=passive diffusion without any covering; D=current alone; E=standard MN response; and F=blanco site. Tristimulus surface colorimetry and Laser Doppler flowmetry were used to measure, respectively, the skin color and the perfusion of the microcirculation. Bioavailability was assessed by quantification of an MN-induced erythema under the different conditions. RESULTS: A significant reduction of the MN-induced erythema was observed with the Chromameter and Laser Doppler measurements for the following treatment modalities: (1) electrically assisted delivery: respectively, 65% and 100%, (2) application under a contact sponge: 66% and 97% and (3) passive diffusion without any covering: 32% and 65%. A significant reduction was equally observed for the site treated with the current alone: 19% and 42%. There was no significant difference between the response after iontophoretic-delivered diclofenac (mode A) and application of diclofenac under a contact sponge (mode B). CONCLUSION: The procedure used enabled us to evaluate the bioavailability of a non-steroidal anti-inflammatory drug in the skin. Under the conditions used, we did not find an increased bioavailability after electrically assisted delivery of diclofenac compared with the passive percutaneous penetration under the contact sponge.