Conference Contribution Details


RE Imhof, P Xiao, EP Berg & MEP De Jesus.
Contributed Talk, World Congress on Non-Invasive Studies of the Skin, Philadelphia, September 2005.



The aim of this study was to develop a method for analysing the decay kinetics of occlusion recovery flux curves at short-times, where instrumental response speed effects are important.

Volar forearm skin of a healthy volunteer was occluded for pre-set times with an 8cm * 3cm Silgel wound dressing. Occlusion recovery flux curves were measured with a condenser-chamber instrument, starting immediately after the removal of the dressing (<5 seconds) and continuing until the signals had settled to steady, final TEWL values. The main experimental results are a family of flux curves for occlusion times in the range 0-15 minutes. The final, steady TEWL values were found to be consistent, with a mean of 9.3 g/(sq.m h) and a CV<2%. The quantity of trapped water was found to increase linearly with occlusion time, with a mean accumulation rate of 1.6 g/(sq.m h) and a CV<11%. Peak flux densities were found to be in the range 14-30 g/(sq.m h), low compared with the ~180 g/(sq.m h) expected from free surface evaporation. The reason is thought to be instrumental response speed: the estimated evaporation times of the small quantities of accumulated surface water are ~7 seconds and less, whereas the 1/e response time of the instrument is ~15 seconds. Other instrumental response time effects include a finite rise-time, a rounding of the peak and a distortion of the decay kinetics at short times. These effects can be corrected to some extent by least-squares convolution methods such as those developed for fluorescence decay analysis. The results of our analysis of these data by this approach are presented.


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