经皮水分散失与角质层水分分布的数值模拟

Numerical modeling of trans-epidermal water loss (TEWL) and water distribution in stratum corneum (SC)

目的:预测经皮水分散失(TEWL)动态变化过程及角质层(SC)中的水分分布状况。方法:本研究将角质层假定为多孔介质,采用混合形式的一维非饱和流动方程与角质层水分吸收等温线的BET模型,建立了角质层中水分迁移的一维孔质模型并进行了数值模拟。采用角质层中水分分布的试验数据及角质层经皮水分散失数据,拟合了水力渗透系数参数并进行了模型验证。结果:讨论了水分体积含量θ对水力渗透系数K的影响:K随着θ的增加而递增,由拟合水分分布试验数据获得的K分布在4.26*10-19与5.41*10-17m·s-1之间。讨论了周围环境湿度RH变化对TEWL稳态值的影响:TEWL随着RH的增加而递减。RH从10%变化到70%的过程中,TEWL模拟值随之变化较小,约从10.50g·m-2·h-1降低到9.56g·m-2·h-1;RH从70%变化到95%的过程中,TEWL模拟值急剧降低,约从9.56g·m-·2h-1降低到0。结论:建立的一维孔质模型可以用于模拟角质层中的水分分布。

Objective： To predict dynamic process of trans-epidermal water loss （TEWL） change and water distribution in stratum comeum （SC）. Methods： One-dimensional mathematical model of moisture migration was set up in SC, using the fluid unsaturated flow equation in mixed form and SC moisture BET absorption isotherm, and then carries out a numerical solution. By means of SC water dis- tribution experimental data and SC TEWL data, the parameter fitting for hydraulic conductivity and further model validation were imple- mented. Results： The effect of water volume fraction 0 on the hydraulic conductivity K was discussed. K rises as 0 increases and K is dis- tributed over the range of 4.26×10^-19 and 5.41×10^-17m· s-1 by fitting water experimental data in SC. The effect of ambient relative humidity （RH） change on steady TEWL value was also discussed. TEWL monotonously increases when RH decreases. TEWL will steeply reduce when RH is more than 70 %, otherwise, TEWL changes slowly. Conclusion： One-dimensional porous model established can be used to simulate the water distribution in SC.