Physical properties of hydrogel wound dressing and its use in low-level laser therapy (LLLT).

Hydrogel dressings are routinely used in the treatment of superficial skin wounds. Due to their excellent transparency, we decided to evaluate their usefulness in laser-based medical procedures. We focused on assessing selected physical properties of HydroAid hydrogel wound dressing, used for low-level laser therapy (LLLT) aka laser biostimulation procedures. For the two wavelengths of 660 and 808 nm used in the biostimulation laser POLARIS 2, a dressing transmittance of 92 and 98%, respectively, was determined. Using a FLIR i7 thermal imaging camera, the changes in temperature distribution across the surface of the dressing were assessed, during a 3-h period following its unpacking and placing on the skin of a patient or leaving it at the ambient temperature. The results of the thermal imaging, as well as temperature measurements using a digital thermometer, showed that the cooling properties of a hydrogel dressing were maintained throughout the entire experiment and that it was capable to keep the temperature at least 5° below the skin/ambient (room) temperature. During the 6-h observation using the holographic microscope, which provided indirect insight into the processes occurring within the hydrogel, only minimum topographical changes (observable at a micrometre scale) were recorded, although dressing thickness and its flexibility decreased significantly with time. Additionally, the possibility to regenerate the hydrogel dressing by treating it with distilled water or a physiological salt solution was tested.