In vitro assessment of water vapour transmission of synthetic wound dressings.

The water vapour transmission rate (WVTR) of 14 commercially available wound dressings (11 hydrocolloids, 2 hydrogels and 1 polyurethane film) was evaluated over 24 and 48 h periods using a modified ASTM standard method (ASTM E96-90). For the 48 h studies a novel microcomputer-controlled apparatus was employed. The dressings exhibited a wide range of WVTRs (76-9360 g m-2 d-1 at 24 h under forced air convection of 0.4 m s-1). The influence of air velocity of 0.4 m s-1 was not significant if the WVTR of the dressing was less than 880 g m-2 d-1 when measured under static air conditions. The influence of outer barrier layers and additional bandages on WVTR was also examined.