Influence of external forces (pressure and shear force) on superficial layer and subcutis of porcine skin and effects of dressing materials: are dressing materials beneficial for reducing pressure and shear force in tissues?

The purpose of this study was to measure the impact of external shear force and pressure on a superficial layer of skin and subcutaneous layer with an underlying bony prominence, and also to verify how the influence of these external forces can be reduced after dressings are applied. For this purpose, an experimental model was prepared, consisting of porcine skin and a Predia sensor capable of measuring pressure and shear force simultaneously. External force was applied to the skin model using a 1 kg weight consisting of metal beads. As a result, the control of the shear force value in the subcutaneous layer became approximately 35% smaller than the control in the superficial layer. The shear forces present in the subcutaneous layer were significantly reduced to within 31-45% when compared with the control values, depending on the dressing applied. Regarding the maximum pressures in the subcutaneous layer, the pressure measured following movement was 2.4 times higher in the control than the static pressure and they were also 1.3-1.8 times higher than the static pressure in all instances with the dressing tested. All the dressing materials tested proved to be effective in reducing pressure in the subcutaneous layer compared with the control. Film dressings and hydrocolloid dressings were more effective than hydropolymer and hydrocellular dressings. From the above results, we conclude that efforts made to reduce shear force and pressure may be clinically important.