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

An anatomically-realistic computational framework for evaluating the efficacy of protective plates in mitigating non-penetrating ballistic impacts

BACKGROUND

A major threat in combat scenarios is the 'behind armor blunt trauma' (BABT) of a non-penetrating ballistic impact with a ballistic protective plate (BPP). This impact results in pressure waves that propagate through tissues, potentially causing life-threatening damage. To date, there is no standardized procedure for rapid virtual testing of the effectiveness of BPP designs. The objective of this study was to develop a novel, anatomically-accurate, finite element modeling framework, as a decision-making tool to evaluate and rate the biomechanical efficacy of BPPs in protecting the torso from battlefield-acquired non-penetrating impacts.

METHODS

To simulate a blunt impact with a BPP, two types of BPPs representing generic designs of threat-level III and IV plates, and a generic 5.56 mm bullet were modeled, based on their real dimensions, physical and mechanical characteristics (plate level-III is smaller, thinner, and lighter than plate level-IV). The model was validated by phantom testing.

RESULTS

Plate level-IV induced greater strains and stresses in the superficial tissues post the ballistic impact, due to the fact that it is larger, thicker and heavier than plate level-III; the shock wave which is transferred to the superficial tissues behind the BPP is greater in the case of a non-penetrating impact. For example - the area under volumetric tissue exposure histograms of strains and stresses for the skin and adipose tissues were 16.6-19.2% and 17.3-20.3% greater in the case of plate level-IV, for strains and stresses, respectively. The validation demonstrates a strong agreement between the physical phantom experiment and the simulation, with only a 6.37% difference between them.

CONCLUSIONS

Our modelling provides a versatile, powerful testing framework for both industry and clients of BPPs at the prototype design phase, or for quantitative standardized evaluations of candidate products in purchasing decisions and bids.

A robotic venous leg ulcer system reveals the benefits of negative pressure wound therapy in effective fluid handling

We applied a market-leading, single-use negative pressure wound therapy device to a robotic venous leg ulcer system and compared its fluid handling performance with that of standard of care, superabsorbent and foam dressings and compression therapy. For each tested product, we determined a metrics of retained, residual, evaporated and (potential) leaked fluid shares, for three exudate flow regimes representing different possible clinically relevant scenarios. The single-use negative pressure wound therapy system under investigation emerged as the leading treatment option in the aspects of adequate fluid handling and consistent delivery of therapeutic-level wound-bed pressures. The superabsorbent dressing performed reasonably in fluid handling (resulting in some pooling but no leakage), however, it quickly caused excessive wound-bed pressures due to swelling, after less than a day of simulated use. The foam dressing exhibited the poorest fluid handling performance, that is, pooling in the wound-bed as well as occasional leakage, indicating potential inflammation and peri-wound skin maceration risks under real-world clinical use conditions. These laboratory findings highlight the importance of advanced robotic technology as contemporary means to simulate patient and wound behaviours and inform selection of wound care technologies and products, in ways that are impossible to achieve if relying solely on clinical trials and experience.

Mechanical and contact characteristics of foam materials within wound dressings: Theoretical and practical considerations in treatment

In the treatment of acute and chronic wounds, the clinical performance of a given foam-based dressing, and, ultimately, the wound healing and cost of care outcomes are strongly influenced by the mechanical performance of the foam material/s within that dressing. Most aspects of the mechanical performance of foam materials, for example, their stiffness, frictional properties, conformability, swelling characteristics and durability, and the overall mechanical protection provided by a foam-based dressing to a wound strongly depend on the microstructure of the foam components, particularly on their microtopography, density and porosity. This article, therefore, provides, for the first time, a comprehensive, self-inclusive compilation of clinically relevant theoretical and practical considerations, based on published analytical and experimental research as well as clinical experience related to the mechanical performance of foams in foam-based wound dressings. The current bioengineering information is useful for establishing understanding of the importance of mechanical properties of foams in foam-based dressings among clinicians and researchers in industry and academia, and other potential stakeholders in the wound care field, for example, regulators and buyers. This information is also particularly important for the development of standardised test methods for the evaluation of foam-based wound dressings and resulting standard mechanical performance metrics for these dressings.

Fluid handling performance of wound dressings tested in a robotic venous leg ulcer system under compression therapy

We designed, developed, built, and utilised a robotic system of a leg with two venous leg ulcers for testing the fluid handling performance of three wound dressing types. The results showed that a foam-based dressing technology is inferior in fluid handling performance when applied to an exuding venous leg ulcer, such that the dressing needs to manage the exudate in a vertical configuration with respect to the ground, that is, so that gravity pulls the exudate to concentrate in a small region at the bottom of the dressing. Moreover, wound dressings containing superabsorbent polymers do not necessarily function equally in fluid handling for venous leg ulcer scenarios, as the extreme requirements from the dressing (to manage the viscous fluid of a vertical and typically highly-exuding wound) appear to distinguish between optimal and suboptimal product performances despite that the tested products contain a superabsorbent, theoretically lumping them together to belong to a so-called 'superabsorbent dressing category'. In other words, it is a false premise to categorise products from different manufacturers into families based on material contents, and then assume that their laboratory or clinical performance is equal, so that from this point they can be judged solely on the basis of price.