Validation of the VapoMeter, a closed unventilated chamber system to assess transepidermal water loss vs. the open chamber Tewameter®

Background/aim: Transepidermal water loss (TEWL) is one of the most important biophysical parameters for evaluating the efficiency of the human skin water barrier. Different approaches exist to measure TEWL. The most commonly used methodology consists of the open chamber diffusion technique in which the water vapor pressure gradient is measured in g/h m(2) according to Fick's law. A typical apparatus is the Tewameter((R)). Recently, a portable device - the VapoMeter - became available with a humidity sensor in a closed chamber. Methods: In the present work, the closed chamber VapoMeter is compared with the open chamber Tewameter((R)) for its applicability to assess TEWL. A comparative study - including parallel in vivo measurements with both devices - was carried out on human forearm skin. Results: It could be concluded that both instruments are reliable tools. A good correlation between recordings (r=0.503-0.966) was found with a consistent feature of measuring higher TEWL values for the Tewameter((R)) than for the VapoMeter. Probe pressure, probe temperature and relative humidity were revealed to be important parameters inducing significant differences in data outcome. Conclusions: From skin barrier damage experiments it became clear that the Tewameter((R)) is able to detect significantly smaller differences than the VapoMeter. In addition, the closed chamber device is currently not sensitive enough to discriminate for the effects induced by diurnal rhythm and fluctuations as a function of time. On the other hand, the small and handy VapoMeter allows more flexibility in measuring protocols and in in-use performance.