In vitro human skin model to evaluate water permeability and determine wound dressings' occlusivity

Wound dressings' occlusivity is directly correlated with water permeability and may affect wound healing. This study evaluated the wound dressings' occlusivity in comparison to their ability to retain water in an in vitro human skin model. Human cadaver skin was stretched over fully filled vials of physiological saline and banded. After 30 minutes, during which equilibrium was established, baseline values for transepidermal water loss (TEWL) were measured. Then an occlusive film was placed over one skin, a semi-occlusive dressing over another and finally 100 microL of a 5% copolymer solution over the third piece of skin, which was then allowed to aerate until it formed a thin membrane. One skin sample was left fully exposed to the air, serving as a blank control. After 30 minutes post-treatment, the TEWL was re-measured for all the samples. TEWL values showed the occlusive film was the most water-impermeable, allowing only a mean of 1.6 g/m(2) hours of water to pass through and thus also showing a significant difference (p < 0.05) in comparison to the blank (untreated) control. Furthermore, the semi-occlusive membrane decreased TEWL but not significantly, whereas the film former appeared to have no effect. We found no significant decrease in TEWL in the semi-occlusive membrane and even in the film former. This in vitro model provides a fast and economical method of screening the effect of occlusivity in wound dressings.