Fluid Handling Dynamics and Durability of Silver-Containing Gelling Fiber Dressings Tested in a Robotic Wound System.

OBJECTIVE: To develop a robotic phantom system containing multiple simulated wound replicates to determine the synergy in fluid absorbency and retention (sorptivity) performances and the post-simulated-use mechanical durability of silver-containing gelling fiber primary dressings when used with a secondary dressing, as per clinical practice. METHODS: Using a robotic system containing six identical wound simulators, the authors tested the sorptivity performances of the Exufiber Ag + (Mölnlycke Health Care, Gothenburg, Sweden) primary dressing (ExAg-polyvinyl alcohol [PVA]) against a market-leading comparator product, when used with a secondary foam dressing. The durability of the primary dressings after simulated use was further investigated through tensile mechanical testing. RESULTS: The ExAg-PVA primary dressing delivered greater fluid amounts for absorbency and retention by the secondary foam dressing, approximately 2- and 1.5-fold more than the comparator dressing pair after 10 and 15 hours, respectively. The ExAg-PVA dressing was also substantially less sensitive to the direction of pulling forces and, accordingly, exhibited post-use mechanical strength that was approximately four and six times greater than that of the other primary dressing (when the latter dressing was tested out-of-alignment with its visible seams) after 10 and 15 hours, respectively. CONCLUSIONS: The dynamics of the sorptivity and fluid sharing between primary and secondary dressings and the effect of directional preference of strength of the primary dressings for adequate durability, resulting in safe post-use removals, have been described. The comparative quantification of these capabilities should help clinical and nonclinical decision-makers select dressings that best meet their patient needs.

The biomechanical efficacy of a hydrogel-based dressing in preventing facial medical device-related pressure ulcers.

Continuous positive airway pressure masks for breathing assistance are used widely during the coronavirus pandemic. Nonetheless, these masks endanger the viability of facial tissues even after a few hours because of the sustained tissue deformations and extreme microclimate conditions. The risk of developing such device-related pressure ulcers/injuries can be reduced through suitable cushioning materials at the mask-skin interface, to alleviate localised contact forces. Here, we determined the facial tissue loading state under an oral-nasal mask while using hydrogel-based dressing cuts (Paul Hartmann AG, Heidenheim, Germany) for prophylaxis, which is a new concept in prevention of device-related injuries. For this purpose, we measured the compressive mask-skin contact forces at the nasal bridge, cheeks, and chin with vs without these dressing cuts and fed these data to a finite element, adult head model. Model variants were developed to compare strain energy densities and effective stresses in skin and through the facial tissue depth, with vs without the dressing cuts. We found that the dry (new) dressing cuts reduced tissue exposures to loads (above the median loading level) by at least 30% at the nasal bridge and by up to 99% at the cheeks, across the tissue depth. These dressing cuts were further able to maintain at least 65% and 89% of their protective capacity under moisture at the nasal bridge and cheeks, respectively. The hydrogel-based dressings demonstrated protective efficacy at all the tested facial sites but performed the best at the nasal bridge and cheeks, which are at the greatest injury risk.

What makes a hydrogel-based dressing advantageous for the prevention of medical device-related pressure ulcers.

The synergistic influences of geometrical, mechanical and thermal mismatches between a skin-contacting medical device and the skin may cause tissue stress concentrations and sharp temperature gradients, both of which contribute to the risk for medical device-related pressure ulcers. In this work, we developed an innovative, integrated experimental bioengineering approach encompassing mechanical stiffness, friction and thermal property studies for testing the biomechanical suitability of a hydrogel-based dressing in prophylaxis of injuries caused by devices. We characterised the viscoelastic stress relaxation of the dressing and determined its long-term elastic modulus. We further measured the coefficient of friction of the hydrogel-based dressing at dressing-device and skin-dressing interfaces, using a tilting-table tribometer. Lastly, we measured the thermal conductivity of the dressing, using a heat-flow meter and infrared thermography-based method. All measurements considered dry and moist conditions, the latter simulating skin perspiration effects. Our results revealed that the long-term stiffness and the thermal conductivity of the hydrogel-based dressing matched the corresponding properties of human skin for both dry and moist conditions. The dressing further demonstrated a relatively high coefficient of friction at its skin-facing and device-facing aspects, indicating minimal frictional sliding. All these properties make the above dressing advantageous for prevention of device-related injuries.