Open AccessComparative metrology of the evaporimeter and the DermaLab® TEWL probe
Author(s) -
Grove Gary L.,
Grove Mary Jo,
Zerweck Charles,
Pierce Elizabeth
Publication year - 1999
Publication title -
skin research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.521
H-Index - 69
eISSN - 1600-0846
pISSN - 0909-752X
DOI - 10.1111/j.1600-0846.1999.tb00196.x
Subject(s) - metrology , nanotechnology , chemistry , environmental science , materials science , optics , physics
Background/aims: Transepidermal water loss (TEWL) measurements are one of the most frequently utilized of the noninvasive bioengineering techniques. Recently, Cortex Technology (Hadsund, Denmark) introduced the DermaLab® system, which can be equipped with a TEWL probe. It is based on the vapor pressure gradient estimation method of Nilsson and, thus, is quite similar to the Servo Med evaporimeter. In this paper, we compare these two commercial instruments under identical experimental conditions using both in vitro studies with physical standards as well as in vivo studies employing human volunteers. Methods: Five different evaporimeters and four different Dermalab® m ain units equipped with one or two TEWL probes were configured in such a way that six freshly calibrated probes of each type could simultaneously be compared in an ambient environment with known relative humidity and temperature values. In follow‐up experiments, each type of instrument was interfaced to a Pentium personal computer, and special data acquisition software was written so that changes in water loss rates could be monitored in real time. These follow‐up studies included comparing water vapor transmission rates through various membranes membranes in vitro and a modified soap chamber test using the volar forearm of adult human volunteers in vivo. Conclusions: Although we found very good agreement between the two instruments, our overall findings clearly demonstrate that the DermaLab® system with a TEWL probe is both more accurate and precise than the Servo Med evaporimeter when used under identical conditions. This is especially obvious when the comparisons between the two types of instruments are based on physical standards. The DermaLab® system with a TEWL probe was also found to be more sensitive and better able to resolve among detergents that differed in harshness. The superior performance of the DermaLab® system can be in part explained by the differences in the way the probes are calibrated by the factory.