Construction of skin impedance model for evaluation of skin barrier functions in case wet-type electrode

Skin has barrier functions which prevent injection of bacteria and perspiration of water. In the field of clinic, there are many situations of failure in barrier functions by stimuli of apply and remove in tape in dialysis patient, by exchange of artificial anal (ostomate), and frequent disinfection. Then, simple evaluating method of skin barrier function is expected non-invasive and quantitatively. So, skin impedance model was proposed in order to develop the evaluation method of barrier functions. Various levels of skin barrier function were prepared artificially by cellulose adhesive tape stripping of forearm stratum corneum. The stripping was performed up to 32 times. Skin impedances were measured with applying PEG liquid wet concentric electrode by impedance meter over the frequency 20 Hz-2 MHz. Frequency characteristics of skin impedance satisfy Cole-Cole arc`s law. It is characterized by four parameters Z<sub>0</sub>, f<sub>m</sub>, C<sub>0</sub>, and β estimated in impedance loci. Skin impedance varies over 1000 times in magnitude and decrease rapidly with increase of striping time. It is cleared that the relationship between magnitude of skin impedance and barrier function. Then, skin impedances were divided to six groups from magnitude in logarithmic scale. The standard values of arc`s parameters to each group were determined. They are, that is, skin impedance models for evaluation of barrier functions. From the consideration of fundamental characteristic in four parameters, when the skin barrier function is failure, Z₀ is lower, f_m is higher, C₀ is bigger, and β is smaller. Because these agree with experimental results, skin impedance models are useful to evaluation of barrier functions. If a skin impedance measurement result on subject is compared with these models, the barrier function in its site could be determined easily.