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.