The evaporative water loss from burns and the water-vapour permeability of grafts and artificial membranes used in the treatment of burns

The evaporative water loss from burns, granulating wounds and donor sites was calculated from measurements of the vapour-pressure gradient of the air layer close to the skin. Soon after burning the mean value and s.e. mean for the rate of evaporation from partial- and full-thickness burns was 178·1 ± 5·5 g m^?2 h^?1 and 143·2 ± 4·5 g m^?2 h^?1 respectively. Uncovered granulating wounds lost water at 214·1 ± 8·4 g m^?2 h^?1, while fresh donor sites during the first postoperative day lost water at 176·0 ± 14·5 g m^?2h^?1, which gradually decreased during the following week to 73·2 ± 12·0 g m^?2 h^?1 as the wound healed.When burned skin was covered with grafts or artificial membranes the evaporative water loss was reduced by a degree depending on the vapour permeability of the cover applied. Compared with the rate of evaporation of water from uncovered tissue, fresh biological dressings reduced the rate of loss by 90 per cent and frozen porcine heterograft skin (Skintec) by 63 per cent. An artificial dressing (Op-Site) reduced the rate of evaporation by 73 per cent while collagen film (Cutycol) and microporous polypropylene film (Epigard) were almost completely permeable to water vapour.