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Prolonged use of continuous positive airway pressure masks, as often required for non-invasive ventilation, involves a risk for facial tissue breakdown due to the sustained deformations caused by tightening of the stiff mask surfaces to the head and the moist environment. The risk of developing mask-related facial injuries can be reduced through suitable cushioning materials placed at the skin-mask interfaces to spread the localised contact forces and disperse the surface and internal tissue stresses. Using an integrated experimental-computational approach, we compared the biomechanical protective performance of three popular foam-based wound dressings to that of a market-lead hydrocolloid dressing when applied to protect the facial skin under a mask. We measured the compressive stiffness properties of the four commercial dressing types in dry and moist conditions, and then fed those to an anatomically realistic finite element model of an adult male head, with an applied simulated mask. Through this process, we calculated the protective efficacy index of each dressing type, indicating the relative contribution of the specified dressing to alleviating facial soft tissue loads with respect to the no-dressing case. The foam-based dressings generally performed substantially better than the hydrocolloid, but foam dressings were also demonstrated to vary by their protective performance.

Objective: The aim of this review article was to identify reported outcomes and measurement instruments used in clinical research on bordered foam dressings in the treatment of complex wounds. Methods: MEDLINE (PubMed interface), Cumulative Index to Nursing and Allied Health Literature (CINAHL), EMBASE, and The Cochrane Library were systematically searched using a combination of key terms including; wounds, bordered foam dressing, and treatment. Studies were included if they (1) targeted an adult population, (2) addressed the treatment of complex wounds with a bordered foam dressing as the primary wound dressing, (3) were retrieved from original research, and (4) were published between 2000 and 2022. There were no restrictions on language or study design. Studies that focused primarily on the prevention of complex wounds were excluded. Data extraction included outcome domains, outcomes, instruments, time points, and outcome measures. The OMERACT Filter 2.0 was used as a conceptual framework for the extraction of outcomes. Results: A total of 24 outcome domains and 82 outcomes were identified. The outcomes were categorised into five core areas: (1) impact on life, (2) dressing performance, (3) pathophysiological manifestations, (4) resource use, and (5) adverse events. Thirtynine outcomes (47.0%) were measured at more than one time point. The most frequently reported time point was ‘at the end of treatment’ (62.7%). Outcomes were measured using self-report instruments, clinical observations, and bio-physiological instruments. Conclusion: This systematic review identified reported outcomes and measurement instruments in research on bordered foam dressings in the treatment of complex wounds. The variety and lack of consistency in terms of instruments, time points and outcome measurements made it difficult to compare data directly across different reported studies. A solution to the variety in outcome reporting across studies in complex wound care, and moreover for the treatment with bordered foam dressings, is the development of a Core Outcome Set (COS). The outcomes in this review article will inform the next steps of developing a COS, where patients, clinicians and researchers will be involved to decide on the final outcomes included in a COS for the treatment of complex wounds with bordered foam dressings.

Diabetic heel ulceration is a serious, destructive, and costly complication of diabetes. In this study, a novel "graded-stiffness" offloading method was proposed. This method consists of heel support with multi-increasing levels of stiffness materials, to prevent and treat heel ulcers. A three-dimensional finite element model of the heel was used to evaluate the novel "graded-stiffness" orthotic device compared to two existing solutions: (1) an insole with a hole under the active ulcer and (2) an insole with a hole filled with a soft material (elastic modulus of 15 kPa). Volumetric exposure evaluation of internal tissues to stress was performed at two volume-of-interests: (1) the area of the heel soft tissues typically at high risk for ulceration, and (2) the soft tissues surrounding the high-risk area. The models predict that the "graded-stiffness" offloading solution is more effective than existing solutions in distributing and reducing heel internal loads, considering both volume-of-interests. Comparing different material gradient combinations for the offloading support reveals considerable variation of the heel stress distribution. In clinical practice, the "graded-stiffness" technological solution enables to form an adaptable and flexible system that can be customized to a specific patient, through adequate selection of the offloading materials, to fit the shape and size of the ulcer. This solution can be made as an off-the-shelf product or alternatively, be manufactured by-demand using 3D printing tools. The proposed novel practical offloading solution has the potential for streamlining and optimizing the prevention and treatment of diabetic heel ulcers.

The aim of this article is to identify and describe clinical practice performance characteristics for bordered foam dressings in the treatment of complex wounds. Our recently published systematic review of outcomes and applied measurement instruments for the use of bordered foam dressings in complex wounds has led to us identifying a range of important clinical and patient-centred issues related to this dressing class. Specifically, here, we focus on an overview of performance criteria in the areas of application, adhesion, exudate management and debridement functions of bordered foam dressings. Our hope is that by highlighting the clinical performance criteria, future testing standards for wound dressings will more closely match our clinical expectations and, thereby, assist clinicians to make better wound treatment choices based on meaningful and clinically relevant dressing product performance standards. complex wounds, complex wound care, treatment, bordered foam dressings, dressing performance.

Using a novel, automated robotic phantom system containing multiple wound simulants, we determined the fluid handling performance of the curea P1 multipurpose dressing vs market-leading comparator superabsorbent and foam-based dressings (FBDs). Specifically, we measured the retained, residual, evaporated, and (potentially occurring) spillover fluid shares for high- vs low-viscosity exudate-simulant test fluids, at 12, 24, and 30 hours postapplication of the dressings. These experiments were conducted for off-loaded ('prone'), non-off-loaded ('supine'), and vertical ('side-lying') simulated body positions. We found that the multipurpose dressing exhibited the best and most robust fluid handling performance across all the test configurations, for both the low- and high-viscosity fluids. The FBD consistently showed the poorest performance compared to the other dressings, rendering it unlikely to be able to manage viscous exudates in ambulant patients (such as when applied to venous leg ulcers) as effectively as the other dressings. The superabsorbent dressing performed better than the foam dressing, but its fluid handling metrics were inferior to those of the multipurpose dressing. The current comparative quantification of the shares of retained, residual, evaporated, and spillover fluid, acquired through standardised laboratory tests, should help decision-makers to select dressings that best meet their patient needs.

Two types of single-use negative-pressure wound therapy systems are currently available to treat surgical wounds: Canister-based and canisterless. This work was aimed to evaluate the performance of a canister-based vs a canisterless system, each with a different negative-pressure setting and technology for fluid management. Continuous delivery of a specified level of negative pressure to the wound bed is hypothesised to be important for promoting surgical wound healing, by achieving continuous reduction of lateral tension in the wound, particularly through decrease of skin stress concentrations around suture insertion sites. To test the above hypothesis, we developed a computational modelling framework, a laboratory bench-test for simulated clinical use and had further conducted a pre-clinical study in a porcine model for closed incision. We specifically focussed on the impact of effective fluid management for continuous delivery of a stable, consistent negative pressure and the consequences of potential losses of the pressure level over the therapy period. We found that a greater (absolute) negative-pressure level and its continuous, consistent delivery through controlled fluid management technology, by removing excess fluid from the dressing, provides far superior biomechanical performances. These conditions are more likely to result in better quality of the repaired tissues.

Sub-epidermal moisture is an established biophysical marker of pressure ulcer formation based on biocapacitance changes in affected soft tissues, which has been shown to facilitate early detection of these injuries. Artificial intelligence shows great promise in wound prevention and care, including in automated analyses of quantitative measures of tissue health such as sub-epidermal moisture readings acquired over time for effective, patient-specific, and anatomical-site-specific pressure ulcer prophylaxis. Here, we developed a novel machine learning algorithm for early detection of heel deep tissue injuries, which was trained using a database comprising six consecutive daily sub-epidermal moisture measurements recorded from 173 patients in acute and post-acute care settings. This algorithm was able to achieve strong predictive power in forecasting heel deep tissue injury events the next day, with sensitivity and specificity of 77% and 80%, respectively, revealing the clinical potential of artificial intelligence-powered technology for hospital-acquired pressure ulcer prevention. The current work forms the scientific basis for clinical implementation of machine learning algorithms that provide effective, early, and anatomy-specific preventive interventions to minimise the occurrence of hospital-acquired pressure ulcers based on routine tissue health status measurements.

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.

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.

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.

Medical device-related pressure ulcers (PUs) (injuries) are a subclass of PUs, associated with pressure and/or shear applied by a medical device onto the skin. Clinical application of a cyanoacrylate liquid skin protectant (CLSP) under the contours of skin-contacting medical devices to shield an intact skin from the sustained mechanical loads that are applied by medical devices is a preventative option, but no computer modelling work has been reported to assess the biomechanical efficacy of such interventions. Here, we investigated the biomechanical protective effect of a polymerised cyanoacrylate coating using three-dimensional, anatomically realistic finite element models of the ear with oxygen cannula and the mouth with endotracheal attachment device, informed by experimental studies. We have compared tissue stress exposures under the devices at these facial sites between conditions where the cyanoacrylate skin protectant has been applied or where the device was contacting the skin directly, without the shielding of the cyanoacrylate coating. The CLSP considerably reduced the skin stress concentration levels and overall tissue stress exposures under the aforementioned medical devices. This demonstrates strong biomechanical effectiveness of the studied cyanoacrylate-based skin protectant in prevention of facial medical device-related injuries at small, curved and thereby difficult to protect facial sites.

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.

Chronic wounds affect millions globally and are a huge financial burden. Whilst there are many wound dressings commercially available to manage these wounds, the complexity of the repair process makes it difficult to select the right dressing for the right wound at the right time. Thus, in this narrative review, we have examined reasons why wounds fail to heal, summarised the pathophysiology of the chronic wound environment and provided an evidence-based, clinically-relevant compilation of the published literature relevant to dressing design and evaluation. This has highlighted the need for a deeper understanding of wound exudates, how exudates change throughout the healing process, and how they are impacted by different dressing materials. Studies assessing biochemical and biophysical changes in exudates throughout the healing process are extremely valuable in this regard, enhancing both our understanding of the wound healing process and the ability to assess dressing performance. In addition, this knowledge allows us to replicate various wound conditions in the laboratory, and develop clinically-relevant models for testing current and new dressings, therefore providing a more comprehensive understanding of how and when they should be used. This approach makes the use of dressings more effective, thereby improving outcomes, and reducing the economic burden of chronic wounds.

This article provides an introduction to the theory of, what is termed, the ‘influence zone’ in the context of negative pressure wound therapy (NPWT). It is a quantitative bioengineering performance measure for NPWT systems, to indicate their effectiveness, namely, how far from the wound bed edges a specific system is able to deliver effective mechano-stimulation into the periwound, and at which intensity. The influence zone therefore provides objective and standardised metrics of one of the fundamental modes of action of NPWT systems: the ability to effectively and optimally deform both the wound and periwound macroscopically and microscopically. Most important is the mechanical deformation of the periwound area to activate cells responsible for tissue repair, particularly (myo)fibroblasts. Notably, the influence zone must extend sufficiently into the periwound to stimulate (myo)fibroblasts in order that they migrate and progress the wound healing process, facilitating the formation of scar tissue, without overstretching the periwound tissues so as not cause or escalate further cell and tissue damage. The inclusion of the influence zone theory within research to investigate the efficacy of NPWT systems facilitates systematic comparisons of commercially available and potentially new systems. This approach has the capacity to guide not only research and development work, but also clinical decision-making. Recently published research found that inducing an effective influence zone first and foremost requires continuous delivery of the intended pressure to the wound bed.

At least 1 in 10 patients develop intraoperative pressure ulcers (PUs). The specific rigid (bio)mechanical constraints that apply in the operation room (OR) and which are unique to this clinical environment, including the inability to periodically reposition patients during surgery and the need to use a ‘stable’ support surface with relatively stiff padding materials lead to soft tissue exposure to extreme conditions of sustained tissue deformations and stress concentrations due to bodyweight forces. Accordingly, the risk of intraoperative PUs, which are triggered and driven by a sustained cell and tissue deformation/stress exposure, is especially high on the operating table (OT). Importantly, the basic OT and OT pad designs are simple and have changed very little over at least a century. The available OT pads, in particular, did not evolve despite the well-known and documented risk for PUs among surgical patients. This article reviews the relevant biomechanical studies published by the author and his research group with respect to the extents of tissue deformations expected on the OT at the body regions which are most susceptible to intraoperative PUs, namely the sacral region and the posterior aspects of the heels. These are the body sites which transfer considerable bodyweight forces in a supine position and contain relatively ‘sharp’ bony prominences compressing relatively thin soft tissue structures, as evident by the magnetic resonance imaging (MRI) studies conducted by the author and his team, as reviewed here. The results reported in this article further highlight the roles of OT pad and positioner materials in reducing localized tissue deformations and thereby, in lowering the risk of intraoperative PUs.

Effective exudate retention by dressings requires close and intimate dressing‐wound contact, immediately and continuously after the dressing application. Any dressing‐wound spaces may allow for build‐up of non‐retained fluids, causing exudate pooling which forms a favourable environment for pathogen growth. Maceration may follow if the pooled exudates spread to peri‐wound skin. Dressings with a claimed 3D‐shape‐conformation technology are commercially available; however, their effectiveness in minimising dressing‐wound gaps has never been scientifically investigated. We present a novel bioengineering methodology for testing the effectiveness of such 3D‐shape‐conformation dressings, using our recently reported robotic phantom system of a sacral pressure ulcer. By means of 3D laser scanning and bespoke software, we reconstructed dressing shapes after simulated use and calculated the goodness‐of‐fit between each dressing (swelled to near‐saturation) and the corresponding wound geometry. Two dressing sizes (10 × 10 cm and 12.5 × 12.5 cm) and two wound depths (2.5 or 2 cm) were considered. All the tested dressings were far from reaching good contact with the (simulated) wounds: Approximately one‐third of the wound volume and nearly half of the wound surface were not in contact with the swelled dressings. Our present findings question whether 3D‐shape‐conformation dressings are effective, by revealing their swelling behaviour which was previously unknown.

Although great strides have been made to tackle hospital-acquired pressure ulcers (HAPUs), there is a need for greater recognition of device-related pressure ulcers (DRPUs), including their causes, management and prevention. This consensus statement, an updated second edition, aims to continue raising awareness of these largely preventable injuries and, crucially, to stimulate action. DRPUs are relatively common and account for a growing proportion of HAPUs. Updated information on the incidence of DRPUs is described in chapter 1. Although it is recognised that DRPUs increase the financial burden of healthcare, there is little formal analysis of their economic impact. This needs to be addressed; robust evidence on the burden of DRPUs and the value that can be released by adopting prevention strategies is needed to help drive action. Our understanding of the pathophysiology of DRPUs has improved significantly over the past few years; this is described in chapter 2. One crucial difference between PUs and DRPUs is that body-weight forces are less significant in DRPUs, with the force being exerted from a device that is typically strapped or taped onto the body. Devices and their securement may generate high stress concentrations in tissues, leading to cell and tissue-damage pathways associated with sustained deformation. As more evidence is published on DRPUs, recurring themes are emerging, as outlined in chapter 3: The most vulnerable patients are bearing the brunt of DRPUs; paediatric and neonatal patients, and all those needing critical care are particularly susceptible. During the COVID-19 pandemic, a new high-risk population (people with severe COVID-19 infection) emerged. They are at increased risk of DRPUs because of their need for prolonged ventilatory support, especially when 'proning' Devices associated with DRPUs are often used to perform essential, life-saving functions. They include continuous positive airway pressure (CPAP) masks or endotracheal tubes. Minimising their use is clearly not an option, so practice innovation is needed Although the most common locations for DRPUs are the face, ears, lower legs and heels, any location where a device comes into close contact with the skin can be at risk. In the same vein, any device, whether needed for a medical purpose or not, has the capacity to cause injury if its use is not properly managed. Vigilance is needed for all patients. What can be done? The importance of routine risk assessment is covered in chapter 4. Although use of a validated risk assessment tool is the vital first step, this will not be enough on its own. Several steps can be taken to ensure the safe use of devices. These are described in chapter 5 and include device repositioning, cushioning with prophylactic dressings and moisture control (only where possible and clinically appropriate). Of key importance is the development of an institutional protocol and champions to ensure all necessary steps are adopted. For any of these changes to be put into practice, awareness of DRPUs needs to increase. A number of proposals are outlined in chapter 6. A change of focus among health professionals and policy makers, along with more investment in education and training, are needed. All patients being managed with a medical device must be considered as at high risk. The pandemic introduced the world to the problem of DRPUs in health professionals caused by the extended wear of personal protective equipment. Health professionals also have a right to expect institutional protocols and provision of devices that protect them from DRPUs. Cutting-edge ideas and technologies that may be available in the future are described in chapter 7. When designing new products, manufacturers of medical devices have a duty of care to investigate the risks of DRPUs associated with their products and mitigate them, wherever possible. Our developing understanding of how the design, structure and materials used in medical devices contribute to DRPUs will help us develop new solutions for tomorrow. The first step is for everyone involved to ask themselves, 'what can I do to help?' There is work to be done-your journey to reduce DRPUs starts here!.

Two distinct design concepts exist for single-use negative pressure wound therapy systems: Canister-based versus canisterless. The canister-based technology provides intrinsic stable delivery of the intended negative pressure, because exudate is constantly transferred from the wound into a canister, thereby preventing dressing saturation. In contrast, with a canisterless system, where delivery of the negative pressure depends on continuous evaporation of wound fluids from its dressing, loss of the intended wound-bed pressure may occur due to dressing saturation. To investigate whether these two designs differ in their mechanobiological effect with respect to magnitudes and distributions of tissue strain fields under the absorptive dressing, termed the influence zone, we integrated computational modelling with an animal study. This influence zone must be of biologically influential strain levels and extend sufficiently into the peri-wound for stimulating fibroblasts to migrate and progress the healing. We found that an effective influence zone requires continuous delivery of the intended pressure to the wound-bed. Loss of negative pressure at the wound-bed below 40 mmHg adversely lowered the peri-wound stimulation around a 120 × 70 mm sized wound to less than one-third of the baseline stimulation, and further pressure decreases to 20 mmHg or lower resulted in complete lack of peri-wound mechano-stimulation.

Significance: Wounds of all types remain one of the most important, expensive, and common medical problems, for example, up to approximately two-thirds of the work time of community nurses is spent on wound management. Many wounds are treated by means of dressings. The materials used in a dressing, their microarchitecture, and how they are composed and constructed form the basis for the laboratory and clinical performances of any advanced dressing. Recent Advances: The established structure/function principle in material science is reviewed and analyzed in this article in the context of wound dressings. This principle states that the microstructure determines the physical, mechanical, and fluid transport and handling properties, all of which are critically important for, and relevant to the, adequate performances of wound dressings. Critical Issues: According to the above principle, once the clinical requirements for wound care and management are defined for a given wound type and etiology, it should be theoretically possible to translate clinically relevant characteristics of dressings into physical test designs resulting specific metrics of materials, mechanical, and fluid transport and handling properties, all of which should be determined to meet the clinical objectives and be measurable through standardized bench testing. Future Directions: This multidisciplinary review article, written by an International Wound Dressing Technology Expert Panel, discusses the translation of clinical wound care and management into effective, basic engineering standard testing requirements from wound dressings with respect to material types, microarchitecture, and properties, to achieve the desirable performance in supporting healing and improving the quality of life of patients.

Background A continuing complication, pressure injuries are due to sustained mechanical loading and tissue deformations, which can then be exacerbated by additional intrinsic and extrinsic risk factors. Although support surfaces are designed to mitigate risk factors for pressure injuries, the presence of a turn and position device (TPD) between the patient and support surface may interfere with how support surfaces affect these risk factors. Objective Report the use of the NPIAP's S3I standard test methods to characterize the performance of a support surface when used in conjunction with three different TPDs. Design Laboratory testing compared three TPDs for Immersion, Envelopment, and Horizontal Stiffness in each of five surface combinations. Main outcome measure Immersion test measures how far mannequin indenter immerses into surface. Envelopment test measures immersion and pressure distribution with hemispherical-indenter with mounted sensor rings. Horizontal Stiffness test measures the shear modulus of the support surface with epicondyle indenter. Main results For the specific TPDs tested here, the one with an adjustable integrated air bladder improved rather than compromised both the envelopment and the immersion of the support surface alone. Additionally, this TPD provided potential protection against sliding and the associated frictional shear forces. Conclusions This paper describes how TPDs should perform in order to help establish which features are needed in a new medical device of this type. Laboratory testing demonstrates it is possible to improve performance of a support surface by applying a TPD as an add-on, thus relieving tissue deformation exposure through more effective pressure redistribution.

The objective of this article is to explain the biophysical principles underlying the design of the subepidermal moisture (SEM) scanner, commercially known as the ‘SEM scanner’. We also describe the mode of operation of the SEM scanner in monitoring tissue health and detecting subtle abnormal changes in tissue physiology in patients and anatomical sites at a risk of a pressure ulcer (PU: also known as a pressure injury). The technology of the SEM scanner was approved last year for sales in the US by the Food and Drug Administration (FDA). The SEM scanner detects changes in fluid contents of human skin and subdermal tissues, to a tissue depth of several millimetres, by measuring ‘capacitance’, an electrical property of the locally examined tissue site to store electric charge. The capacitance of tissues, called ‘biocapacitance’, is strongly affected by the amount of fluid (water) in the tissue. When the first cells die in a forming PU, inflammatory signalling causes the permeability of blood vessel walls to increase and oedema to develop. Simply, the scanner detects the early appearance of oedema, which is called ‘micro-oedema.’ Calculation of a ‘SEM-delta’ value, which compares biocapacitance measurements, acquired across several tissue sites, some of which are healthy and others where the PU may evolve, eliminates potential effects of systemic changes in tissue fluid contents and provides a consistent quantitative measure of the tissue health conditions at the monitored anatomical site. Here, we describe SEM scanner technology, how it operates and has been laboratory tested (in computer simulations, in silico) before commercial launch. We explain why targeting the physical biomarker of oedema leads to the documented success of the SEM scanner in the multiple published clinical trials, proving its ability to early detect PUs that form under intact skin.

Prone positioning is used for surgical access and recently in exponentially growing numbers of coronavirus disease 2019 patients who are ventilated prone. To reduce their facial pressure ulcer risk, prophylactic dressings can be used; however, the biomechanical efficacy of this intervention has not been studied yet. We, therefore, evaluated facial soft tissue exposures to sustained mechanical loads in a prone position, with versus without multi‐layered silicone foam dressings applied as tissue protectors at the forehead and chin. We used an anatomically realistic validated finite element model of an adult male head to determine the contribution of the dressings to the alleviation of the sustained tissue loads. The application of the dressings considerably relieved the tissue exposures to loading. Specifically, with respect to the forehead, the application of a dressing resulted in 52% and 71% reductions in soft tissue exposures to effective stresses and strain energy densities, respectively. Likewise, a chin dressing lowered the soft tissue exposures to stresses and strain energy densities by 78% and 92%, respectively. While the surgical context is clear and there is a solid, relevant need for biomechanical information regarding prophylaxis for the prone positions, the projected consequences of the coronavirus pandemic make the present work more relevant than ever before.

PURPOSE: To employ a finite element (FE) stress model to simulate laser in situ keratomileusis (LASIK) surgery and its biomechanical consequences. METHODS: The basic geometrical model we used for the cornea was patient-specific on which we manually incorporated seven simulations: three simulations evaluating the effect of a 120, 140 and 180 μm flap (without ablation); three simulations evaluating ablation depths of 40, 80 and 120 μm (with a 120 μm flap); and one control model, without any simulated surgical intervention. RESULTS: In all simulations, stress values were greatest in the centre of the cornea. Furthermore, when comparing the different treatments, stress values were highest in the cornea with the deepest ablation, and were lowest in the non-treated cornea. Specifically, peak effective stresses were 0.031, 0.028 and 0.025 MPa in 120, 80 and 40 µm ablation depths, respectively. CONCLUSIONS: In our model, the depth of tissue penetration using ablation or flap creation was correlated with tissue loads—the thinner the residual stromal bed is, the greater are the stresses occurring as a result of the same IOP. RELEVANCE: We based our model geometry on patient specific scans, allowing for customisation of the treatment to the patient’s corneal structure.

The objective of this article is to formulate a new bioengineering theoretical framework for modelling the biomechanical efficacy of cyanoacrylate skin protectants, with specific focus on the Marathon technology (Medline Industries, Inc., Northfield, Illinois) and its modes of action. This work details the bioengineering and mathematical formulations of the theory, which is based on the classic engineering theories of flexural stiffness of coated elements and deformation friction. Based on the relevant skin anatomy and physiology, this paper demonstrates: (a) the contribution of the polymerised cyanoacrylate coating to flexural skin stiffness, which facilitates protection from non-axial (eg, compressive) localised mechanical forces; and (b) the contribution of the aforementioned coating to reduction in frictional forces and surface shear stresses applied by contacting objects such as medical devices. The present theoretical framework establishes that application of the cyanoacrylate coating provides considerable biomechanical protection to skin and subdermally, by shielding skin from both compressive and frictional (shearing) forces. Moreover, these analyses indicate that the prophylactic effects of the studied cyanoacrylate coating become particularly strong where the skin is thin or fragile (typically less than ~0.7 mm thick), which is characteristic to old age, post-neural injuries, neuromuscular diseases, and in disuse-induced tissue atrophy conditions.

Background:Penile clamps provide a means of preventing urinary incontinence in males following radical prostatectomy. In order for the devices to function, significant mechanical loads need to be applied to the penile tissues to close the urethra. However, such loads have the potential to cause damage to the vulnerable skin and underlying soft tissues. Accordingly, the study aimed to estimate the magnitudes of tissue deformations resulting from penile clamp application in three individual cases.Methods:Three individuals were recruited who currently use penile clamps to manage urinary incontinence following radical prostatectomy. Magnetic resonance images (MRI) of the penis were taken to produce a series of high contrast coronal and sagittal images both before and during the application of two commercially available clamps, modified for MRI compatibility. Tissue thickness measurements were estimated with the clamps in-situ and normalised to the unloaded baseline state.Results:The estimated magnitude of tissue deformations resulting from clamp application ranged between 68% and 84%. There were minimal differences in these deformations between the clamp designs, both of which appeared effective in closing the urethra. Local stress concentrations were observed in the tissues, which were deformed around the shape of the clamp.Conclusions:MRI enabled quantification of local tissue deformation during penile clamp application. The results revealed that clamps created large tissue deformations in all three cases, regardless of design. This information could inform the development of new clamp designs and materials to minimise the potential for tissue damage.Level of evidence:4

The 2019 novel coronavirus disease (COVID-19) pandemic has brought the effects of device-related pressure ulcers (DRPU) into sharp focus. With the increased use of personal protective equipment (PPE), including face masks, continuous positive airway pressure (CAPP) masks and other devices, the incidence of DRPUs among health professionals and patients alike has risen starkly. As such, the Journal of Wound Care (JWC) consensus document, Device-related pressure ulcers: SECURE prevention, published in February 2020, is more relevant than ever. To help support patients and frontline health professionals, JWC is republishing the consensus in a digital format, along with a new introductory article outlining the DRPU risks posed by PPE and other medical devices used by patients and health professionals during the pandemic, and how the skin damage can be avoided. The aim is to provide frontline staff with a clear, simple strategy on how to prevent the risk of personal skin damage and/or DRPU during the pandemic, as well as point them in the direction of more indepth guidance on long-term strategies for prevention, for both themselves and patients.

The altered biomechanical function of the knee following partial meniscectomy results in ongoing articular cartilage overload, which may lead to progressive osteoarthritis (OA). An artificial medial meniscus implant (NUsurface® Meniscus Implant, Active Implants LLC., Memphis, TN, USA) was developed to mimic the native meniscus and may provide an effective long-term solution for OA patients, alleviate pain, and restore joint function. The goal of the current study was to investigate the potential effect of an artificial medial meniscus implant on the function of the lateral compartment of the knee and on the potential alterations in load distribution between the two compartments under static axial loading, using advanced piezo-resistive sensors. We used an integrated in situ/in vivo experimental approach combining contact pressure measurements of cadaveric knees with MRI joint space measurements of 72 mild OA patients. We employed this integrated approach to evaluate the mechanical consequences in both the medial (treated) and lateral knee compartments of two levels of meniscectomy and implantation of an artificial meniscus implant. Partial and subtotal meniscectomies of the medial meniscus resulted in statistically significant decrease in contact areas (p = 0.008 and p

We reported the efficacy of soft silicone multilayered foam dressings in preventing intraoperatively acquired pressure injuries (IAPIs) in the prone position using a Relton‐Hall frame (BOSS trial). The aim of this study was to clarify the incidence and extract the risk factors for IAPIs in cases in which polyurethane film dressing was used against IAPIs before the BOSS trial period. This study conducted as a retrospective dual‐center cohort study between August 2014 and Jun 2015 using the medical records in the operating room. The incidence of IAPIs that developed within 24 hours after surgery was 7.1% (7/99). The multivariate logistic regression analysis revealed that body mass index (BMI) (P = .0016, odds ratio [OR]: 1.22, 95% confidence interval (CI) 1.08‐1.4) and length of surgery (P < .0001, OR 2.47, 95% CI 1.86‐3.51) were independently associated with the development of IAPIs. Since high BMI was not extracted in BOSS trial, we conclude that the application of soft silicone multilayer foam dressings is important for preventing the development of IAPIs in patients with high BMI values.

Head‐of‐bed (HOB) elevation is a common clinical practice in hospitals causing the patient's body to slide down in bed because of gravity. This migration effect likely results in tissue shearing between the sacrum and the support surface, which increases the risk for pressure injuries. StayInPlace (HillRom Inc.) is a commercial migration‐reduction technology (MRT) incorporated in intensive care bedframes. Yet, the effects of migration‐reduction on tissue shear stresses during HOB elevation are unknown. We analysed relationships between migration and resulting sacral soft tissue stresses by combining motion analysis and three‐dimensional finite element modelling of the buttocks. Migration data were collected for 10 subjects, lying supine on two bedframe types with and without MRT, and at HOB elevations of 45°/65°. Migration data were used as displacement boundary conditions for the modelling to calculate tissue stress exposures. Migration values for the conventional bed were 1.75‐ and 1.6‐times greater than those for the migration‐reduction bed, for elevations of 45° and 65°, respectively (P

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Pressure ulcers (PUs) are one of the most prevalent adverse events in acute and chronic care. The root aetiological cause of PUs is sustained cell and tissue deformations, which triggers a synergistic tissue damage cascade that accelerates over relatively short time periods. Changes in skin microclimate conditions are known to indirectly contribute to PU-risk levels or to exacerbation of existing wounds. It is therefore surprising that information concerning heat accumulation under dressings is poor. Here, we aimed to investigate the effects of dressings on the microclimate of weight-bearing buttocks skin in 1-hour supine lying sessions. Using a novel and originally developed experimental-computational approach, we compared the combined influence of the mechanical and thermal properties of a polymeric membrane dressing (PolyMem, Ferris Mfg. Corp., Fort Worth, TX) on skin microclimate under and near the dressings with those of a standard placebo foam dressing. We specifically identified the thermal conductivity properties of dressings as being highly important in the context of protective dressing performances, given its association with potential heat accumulation under dressings. Accordingly, this article highlights, for the first time in the literature, the relevance of thermal properties of a dressing in effectively mitigating the risk of developing PUs or aggravating an injury, and offers a systematic, methodological bioengineering process for assessing the thermal performances of dressings.

Alleviation of localised, sustained tissue loads and microclimate management are the most critical performance criteria for materials in use for pressure ulcer prevention, such as in prophylactic dressings, padding or cushioning. These material performance criteria can be evaluated by calculating the extents of matching between the material stiffness (elastic modulus) and the thermal conductivity of the protective dressing, padding or cushioning with the corresponding properties of native skin, separately or in combination. Based on these bioengineering performance criteria, hydrocolloids, which are commonly used for prophylaxis of medical device-related pressure ulcers, exhibit poor stiffness matching with skin. In addition, there is remarkable variability in the modulus and thermal conductivity matching levels of different material types used for pressure ulcer prevention, however, it appears that among the materials tested, hydrogels provide the optimal matching with skin, followed by gels and silicone foams. The stiffness matching for hydrocolloids appears to be inferior even to that of gauze. This article provides quantitative performance criteria and metrics for these evaluations, and grades commonly used material types to biomechanically guide clinicians and industry with regards to the selection of dressings for pressure ulcer prevention, both due to bodyweight forces and as a result of applied medical devices.

Pressure ulcers are soft-tissue damage associated with tissue exposure to sustained deformations and stress concentrations. In patients who are proned for ventilation or surgery, such damage may occur in the superficial chest tissues that are compressed between the rib cage and the support surface. Prophylactic dressings have been previously proven as generally effective for pressure ulcer prevention. In this study, our goal was to develop a novel computational modelling framework to investigate the biomechanical efficacy of a dressing with a soft cellulose fluff core in protecting proned surgical patients from chest pressure ulcers occurring on the operating table, due to body fixation by the Relton-Hall frame. We compared the levels of mechanical compressive stresses developing in the soft chest tissues, above the sternum and ribs, due to the trunk weight, whilst the body is supported by the Relton-Hall frame pads, with versus without the prophylactically applied bilateral dressings. The protective efficacy index for the extremely high stresses, above the 95th-percentile, were 40.5%, 25.6% and 24.2% for skin, adipose and muscle, respectively, indicating that the dressings dispersed elevated soft-tissue stresses. The current results provide additional support for using soft cellulose fluff core dressings for pressure ulcer prophylaxis, including during surgery.

The effectiveness of wound dressing performance in exudate management is commonly gauged in simple, non-realistic laboratory setups, typically, where dressing specimens are submersed in vessels containing aqueous solutions, rather than by means of clinically relevant test configurations. Specifically, two key fluid-structure interaction concepts: sorptivity-the ability of wound dressings to transfer exudate, including viscous fluids, away from the wound bed by capillary action and durability-the capacity of dressings to maintain their structural integrity over time and particularly, at removal events, have not been properly addressed in existing test protocols. The present article reviews our recent published research concerning the development of clinically relevant testing methods for wound dressings, focussing on the clinical relevance of the tests as well as on the standardisation and automation of laboratory measurements of dressing performance. A second objective of this work was to compile the experimental results characterising the performance of gelling fibre dressings, which were acquired using advanced testing methods, to demonstrate differences across products that apparently belong to the same "gelling fibre" family but differ remarkably in materials, structure and composition and, thereby, in performance.

Sustained soft tissue exposure to localised deformations is a trigger for the formation of pressure ulcers. Immersion and envelopment are critical benchmarks that determine comfort and the pressure ulcer risk mitigation, as they have considerable influence on tissue stress concentrations near bony prominences. In the present study, we developed a computer modelling framework for quantifying the extent by which optimal envelopment disperses tissue stress concentrations near the sacrum. To compare the risk of developing a sacral pressure ulcer while lying supine on a regular foam mattress with respect to lying on a specialised, minimum tissue deformation mattress (which closely conforms to the body contours), we used a three-dimensional anatomically-realistic model of the adult female buttocks. The strains and stresses in the subdermal soft tissues reached peak values of 65% and 2.4 kPa for the regular mattress, respectively, but always remained below 45% and 1.2 kPa for the minimum tissue deformation mattress, which indicates longer safe times for supine support on the latter mattress. Our work demonstrates that alleviation of localised, sustained stress concentrations through good immersion and envelopment of the support surface protects from pressure ulcers, and has the potential to relieve chronic pain which is associated with the pressure ulcer risk.

Among the advanced wound dressing types, superabsorbent (SA) dressings form an important class of dressings, particularly for the management of medium to highly exuding wounds. However, SA dressings are not all made the same. This educational article describes distinct, common SA dressing designs, which differ fundamentally in structure and composition, and, thereby, in their exudate absorption function and clinical efficacy. The diverse design families of SA dressings, including dressings with an SA polymer-sheet core, versus dressings with an air laid core, where the SA polymer grains are embedded in fluff, relate to different manufacturing processes, production techniques and associated fabrication costs. These fundamental structural and material differences across SA dressing designs from different manufacturers naturally lead to wide variations in the fluid handling characteristics of the products, which are analysed here using both theoretical and experimental bioengineering laboratory approaches. This work is primarily aimed at promoting critical thinking among health professionals who should ask manufacturers to present relevant testing data for an informed clinical decision-making with regards to the choice of the safest and best performing SA dressing for each treated wound case.

Background Ventilating critically ill patients with acute respiratory distress syndrome in the prone position is a life-saving strategy, but it is associated with adverse consequences such as skin damage. Aim To identify, review and evaluate international proning and skin care guidelines and make an inventory of commonly used equipment and training resources. Design A gap analysis methodology was applied. Methods 1) Comprehensive search and evaluation of proning and skin care guidelines, 2) extensive search and listing equipment and educational resources, and 3) international consultation with 11 experts (8 countries). Data sources A variety of sources researched through July 2021 were used to identify relevant literature: (1) scientific literature databases and clinical trials registries, (2) intensive care and wound care associations, (3) healthcare organisations, (4) guideline development organisations, and (5) the Google search engine. Eleven international experts reviewed the literature and provided insights in two, 2-h online sessions. Findings The search yielded 24 guidelines. One clinical practice guideline had high methodological quality. Twenty-five devices/equipment and sixteen teaching materials were identified and discussed with the expert panel. The gap analysis identified a lack of concise, accessible, evidence-based guidelines and educational materials of short duration. Conclusion This analysis forms the basis for designing a competency-based education and training intervention for an interdisciplinary team caring for the skin of critically ill patients in the prone position. Impact The results can assist the multidisciplinary team to review their current protocol for prone positioning. This is a first step in developing a training package for clinicians.