Department of Clinical Science, Intervention and Technology, Karolinska Institutet, SE-14186 Stockholm, Sweden.
Physiol Meas. 2011 Jan;32(1):1-18. doi: 10.1088/0967-3334/32/1/001. Epub 2010 Nov 19.
The functional integrity and pathology of the skin is reflected in its electrical impedance spectra. Non-invasive electrical impedance measurements of intact skin are dominated by the high impedic stratum corneum in low frequencies and with increasing frequency gradually comes to be dominated by viable skin. Models of this multi-layered organ can increase our understanding of the actual physical properties/dimensions and facilitate better diagnostics in certain applications. Therefore, a mathematical model considering conservation of charge in the various layers of the skin and adjacent electrodes is derived and validated with experimental findings; the latter was carried out on 60 young female subjects. The impact of the stratum corneum thickness, inundation, solvent and cohort size on the electrical properties is studied. Both model parameters and experimental conditions were adjusted for calibration and subsequent validation of the model with measurements. It is found that both the model's thickness of the stratum corneum as well as experimental soaking conditions (both time and saline concentration) affect the fit between the model and measurements. It is concluded that it is essential that the electrical properties of the skin are presented in the context of the ion concentration (if a moisturizer is employed) as well as the soaking time. Further refinements should be made to determine even more accurate dielectrical properties of the stratum corneum and viable skin layers by accounting for the true skin thickness and the heterogeneity of the skin layers-this would be useful in applications where subtle alterations in the skin are of interest.
皮肤的功能完整性和病理学反映在其电阻抗谱中。完整皮肤的非侵入性电阻抗测量主要由高阻抗的角质层在低频下主导，随着频率的增加，逐渐由有活力的皮肤主导。这种多层器官的模型可以增加我们对实际物理性质/尺寸的理解，并在某些应用中促进更好的诊断。因此，推导并验证了一个考虑皮肤各层和相邻电极中电荷守恒的数学模型；后者是在 60 名年轻女性受试者上进行的。研究了角质层厚度、浸润、溶剂和队列大小对电特性的影响。对模型参数和实验条件进行了调整，以对模型进行校准，并随后对测量结果进行验证。结果发现，模型的角质层厚度和实验浸泡条件（时间和生理盐水浓度）都影响模型与测量结果的拟合程度。结论是，在考虑到离子浓度（如果使用保湿剂）以及浸泡时间的情况下，皮肤的电特性非常重要。进一步的改进应该考虑到真实的皮肤厚度和皮肤层的异质性，以确定更准确的角质层和有活力的皮肤层的介电特性，这在对皮肤细微变化感兴趣的应用中非常有用。
