title: A portable device using a closed chamber system for measuring transepidermal water loss: comparison with the conventional method.
abstract: OBJECTIVE
  The measurement of transepidermal water loss (TEWL) is frequently used to evaluate the barrier function of the stratum corneum (SC) of diseased skin in vivo, as well as normal skin damaged by external injurious agents. For this purpose, most people use biophysical instruments, based on an open chamber system, measuring the water vapor pressure gradient produced above the skin surface by vapor passing through the SC barrier. Recently, we tested a new portable device (Model H4300 NIKKISO-YSI CO., LTD., Tokyo, Japan) based on a closed chamber system. Its measuring principle is based on a computed TEWL estimation, from the progressive increase in relative humidity inside a closed chamber, due to continuous water evaporation from the skin surface on which the chamber is placed.
  
  
  METHODS
  We conducted an in vivo comparative study between the new portable device and a conventional method, using the DermaLab (Cortex Technology, Hadsund, Denmark), on both healthy and diseased skin surfaces, under well-controlled, standardized, experimental conditions (21 degrees C and 50% relative humidity).
  
  
  RESULTS
  We found that the sensitivity of the new device was similar to that of the DermaLab. For example, the poor SC barrier function of normal facial skin was clearly demonstrated by significantly higher TEWL values than those of the extremities (P<0.0001). The compromised barrier function of the lesional skin of atopic dermatitis and psoriasis was also demonstrated in a severity-dependent fashion. However, the TEWL values measured with the new device were much lower than those obtained with the DermaLab, probably reflecting differences in the methodological principles. Nevertheless, they correlated well with those of the latter method (P<0.001). For the instruments compared in the present study, we found the following equation useful for conversion: [corresponding value obtained with the DermaLab]= 1.42 x [the recorded value with Nikkiso-YSI Model H4300] + 1.892.
  
  
  CONCLUSIONS
  We consider this closed chamber system practical because it can be carried easily and its portability enables TEWL measurements to be taken in any location, without ensuring a special environment against air turbulence. Moreover, it is far less expensive than other devices currently available.
authors: Department of Dermatology, Tohoku University School of Medicine, Sendai, Japan.
authors: Hachiro
authors: H
authors: Tagami
authors: Hiromi
authors: H
authors: Kobayashi
authors: Katsuko
authors: K
authors: Kikuchi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001703:Biophysics / Q000295:instrumentation*; D003876:Dermatitis, Atopic / Q000378:metabolism; D006801:Humans; D008875:Middle Aged; D011565:Psoriasis / Q000378:metabolism; D012867:Skin / Q000378:metabolism*; D013696:Temperature; D014867:Water / Q000378:metabolism*; D014870:Water Loss, Insensible
chemical_list: D014867:Water