Evaluation of a hand-held evaporimeter (VapoMeter^®) for the measurement of transepidermal water loss in healthy dogs

In humans, transepidermal water loss (TEWL) is measured by noninvasive techniques using either open- or closed-chamber instruments. The aim of this study was to investigate the use of a hand-held, closed chamber device (Vapometer) to measure TEWL in canine skin. Repeated measurements obtained from multiple body sites in one short and one long-coated dog had mean coefficients of variation ranging from 20% to 33%. In the short-coated dog, TEWL ranged from a mean of 5.8 g/m(2)/h on the ventral abdomen to 24.4 g/m(2)/h between the shoulders. In the long-coated dog, mean TEWL values ranged from 26.3 g/m(2)/h on the right chest wall to 51.3 g/m(2)/h in the right axilla. TEWL readings differed significantly at different body sites and showed significant day-to-day variation. In a comparison of a further 20 dogs, TEWL readings obtained from the lateral thorax differed significantly between dogs. Furthermore, in seven of the twenty dogs, readings differed significantly when one side was compared with the other. The Vapometer was able to measure TEWL in canine skin and yielded values similar to those previously reported in the literature using other devices. However, for use in clinical studies, the significant site to site, day-to-day and dog to dog variations would make changes induced by disease, drugs, dietary supplements or topical agents very difficult to reliably detect.