Evaporative water loss and epidermis regeneration in partial-thickness wounds dressed with a fluid-retaining versus a clot-inducing wound covering in guinea pigs.

The effects of a new high vapour permeable poly-(ether urethane) (PEU) wound covering on evaporative water loss (EWL) and epidermis regeneration in partial-thickness wounds in guinea pigs were investigated and compared with an occlusive wound covering (OpSite) and air-exposed controls. It was also assessed whether the EWL reflected the phases of epidermis regeneration. In PEU-covered wounds, the initially raised EWL of 100 gm-2h-1 decreased in four days to 30 gm-2h-1, the same level as in occluded wounds. In control wounds this level was only reached after seven days, reflecting slower epidermis regeneration. The results showed that triphasic EWL behaviour corresponded to the sequence of wound healing. There was (1) a constant raised EWL until epidermal resurfacing is complete, (2) a fast EWL decrease during parakeratotic keratinization, and (3) a gradual normalization of the EWL during maturation of the stratum corneum. In wounds covered with OpSite this phasic EWL behaviour did not occur, owing to forced reduction because of the relatively impermeable covering. It was concluded that the PEU wound covering has an ideal water vapour permeance of 22.2 gm-2h-1 kPa-1, as can be seen in the accelerated epidermis regeneration and fast EWL reduction in partial thickness wounds in guinea pigs.