What makes a good head positioner for preventing occipital pressure ulcers

Patients who are stationary endure prolonged soft tissue distortions and deformations at contact areas between their body and the support surface, which may lead to the onset of pressure ulcers (PUs) over time. A novel technology for patient positioning employs innovation in materials science, specifically viscoelastic materials with shape memory properties that compose the Z‐Flo™ head positioner (Mölnlycke Health Care, Gothenburg, Sweden). Head positioners are generally known to reduce the occurrence of PUs in scalp tissues and the ears, but quantitative assessments of their biomechanical efficacy are missing in the literature. To determine potential differences in mechanical loads formed in the soft tissues of the back of the head while in contact with 2 head positioner types, Z‐Flo vs flat medical foam, we developed 2 comparable finite element model configurations, both including the same 3‐dimensional adult head. For both model variants, stresses in skin and fat peaked at the occiput. The skin at the back of the resting head is subjected to greater stress values with respect to fat; however, the Z‐Flo positioner reduced the exposure of both skin and fat tissues to elevated stresses considerably (by a factor of 3) compared to the medical foam support. We found the Z‐Flo device effective in reducing tissue loads at the surface of the head as well as internally in scalp tissues, with a particular strength in reducing internal tissue shear. The Z‐Flo device achieves this protective quality through highly effective immersion and envelopment of the back of the head, generated in the process of manual moulding of the device in preparation for use. Additional protection is achieved through the viscoelastic response of the filling material of this positioner, which relaxes promptly and considerably under the weight of the head (by more than 2‐fold within approximately 1 s) as opposed to the elastic recoil of the foam that pushes back on scalp tissues.     

The contribution of a directional preference of stiffness to the efficacy of prophylactic sacral dressings in protecting healthy and diabetic tissues from pressure injury: computational modelling studies

The sacral region is the most common site for pressure injuries (PIs) associated with lying in bed, and such sacral PIs often commence as deep tissue injuries (DTIs) that later present as open wounds. In complex patients, diabetes is common. Because, among other factors, diabetes affects connective tissue stiffness properties, making these tissues less able to dissipate mechanical loads through physiological deformations, diabetes is an additional biomechanical risk factor for PIs and DTIs. A preventive measure with established successful clinical outcomes is the use of sacral prophylactic dressings. The objective of this study has been to expand our previous work regarding the modes of action and biomechanical efficacy of prophylactic dressings in protecting the soft tissues adjacent to the sacrum by specifically examining the role of a directional stiffness preference (anisotropy) of the dressing while further accounting for diabetic tissue conditions. Multiple three‐dimensional anatomically detailed finite element (FE) model variants representing diabetic tissue conditions were used, and tissue loading state data were compared with healthy tissue simulations. We specifically compared soft tissue exposures to elevated internal shear stresses and strain energy densities (SED) near the sacrum during supine weight bearing on a standard (foam) hospital mattress without a dressing, with a prophylactic dressing lacking directional stiffness preferences and with an anisotropic dressing. Our results have clearly shown that an anisotropic dressing design reduces the peak tissue stresses and exposure to sustained tissue deformations in both healthy and diabetic cases. The present study provides additional important insights regarding the optimal structural and material design of prophylactic dressings, which in turn, informs clinicians and decision makers regarding beneficial features.     

Evaluation of facial tissue stresses under medical devices post application of a cyanoacrylate liquid skin protectant: An integrated experimental‐computational study

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.     

Modelling an adult human head on a donut‐shaped gel head support for pressure ulcer prevention

Patients who are stationary endure prolonged pressures and shear loads at contact areas between their body and the support surface, which over time may cause pressure ulcers (PUs). Donut‐shaped gel head supports are commonly used to protect the occiput, which is among the most common anatomical sites for PUs; however, the biomechanical efficacy of these devices is unclear. To investigate their effects on scalp tissues, we have used our three‐dimensional anatomically realistic finite element model of an adult head, to which we have added a donut‐shaped gel head support. We then compared the occipital scalp tissue loads'' occurrence while the donut‐shaped gel head support is in use with those associated with a fluidised head positioner and a standard medical foam. The donut‐shaped gel head support inflicted the greatest exposure to tissue mechanical stresses, particularly to the high (and therefore dangerous) stress domain, when compared to the other positioners. We concluded that while the donut‐shaped gel head support is designed to avert tissue loads away from the occiput and disperse them to the surroundings, in practice, it fails to do so. In fact, the donut‐shaped gel head support imposes the head‐weight forces to transfer through a relatively narrow ring of scalp tissues, hence increasing the risk of developing occipital PUs.     

Computational studies of the biomechanical efficacy of a minimum tissue deformation mattress in protecting from sacral pressure ulcers in a supine position

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.     

Sub‐epidermal moisture measurement: an evidence‐based approach to the assessment for early evidence of pressure ulcer presence

This paper aims to discuss the literature pertaining to early pressure‐shear induced tissue damage detection, with emphasis on sub‐epidermal moisture measurement (SEM). The current method for pressure detection is visual skin assessment (VSA); however, this method is fraught with challenges. Advances in early detection of pressure ulcers are reported in the literature and mainly involve measuring inflammation markers on weight‐bearing anatomical areas in order to capture the first signs of tissue damage. One novel technique currently in use is SEM measurement. This biophysical marker is the product of plasma that leaks as a response to local inflammation arising due to pressure‐shear induced damage over bony prominences. The early detection of tissue damage is beneficial in two different ways. First, it enables early intervention when the damage is still microscopic and reversible and, therefore, has the potential to prevent further aggravation of healthy surrounding tissue. This arises by avoiding the causation of the problem and stopping the knock‐on effect of inflammation, especially when the rapid pressure ulceration pathway of deformation is in place. Second, when the slow ischaemic‐reperfusion related mechanism is undergoing, cell death can be avoided when the problem is identified before the cell reaches the “death threshold,” completely averting a pressure ulcer.     

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.     

Utility of a sensor‐based technology to assist in the prevention of pressure ulcers: A clinical comparison

Detection of subcutaneous tissue damage before it is visible can trigger early intervention and decrease hospital‐acquired pressure ulcer (HAPU) rates. The objective of this two‐phase study was to evaluate the clinical utility of the Sub‐Epidermal Moisture (SEM) Scanner (Bruin Biometrics (BBI), LLC), a hand‐held device that assesses increases in interstitial fluid or subepidermal moisture, indicating early tissue damage. Phase 1: Patients were provided standard‐of‐care risk assessment and interventions and were scanned with the SEM Scanner, but the resulting SEM scores were not used to determine interventions. This gave a baseline pressure ulcer incidence rate. Phase 2: This phase is the same as Phase 1 except the resulting SEM scores were used in conjunction with risk assessment scores to determine appropriate interventions and care planning. In Phase 1, 12 of the 89 subjects or 13.5% developed visible pressure ulcers—4 Stage I''s, 6 Stage II''s, 1 Stage III, and 1 deep tissue injury. In Phase 2, 2 of the 195 subjects or 1.0% developed visible pressure ulcers—1 Stage I and 1 Stage II. Patients in Phase 2 were more incontinent, less mobile, and had longer lengths of stay than those in Phase 1. Use of the Scanner resulted in a 93% decrease in HAPU. No deep injuries developed in Phase 2.     

The biomechanical protective effects of a treatment dressing on the soft tissues surrounding a non‐offloaded sacral pressure ulcer

Patients who are immobile endure prolonged bodyweight‐related compressive, tensional and shear loads at their body‐support contact areas that over time may lead to the onset of pressure ulcers (PUs). Approximately, one‐third of the common sacral PUs are severe and classified as category 3 or 4. If a PU has occurred, off‐loading is the basic, commonly accepted clinical intervention; however, in many situations, complete off‐loading of sacral PUs is not possible. Minimising the exposure of wounds and their surroundings to elevated mechanical loads is crucial for healing. Accordingly, in the present study, we aimed to investigate the biomechanical effects of the structural and mechanical properties of different treatment dressings on stresses in soft tissues surrounding a non‐offloaded sacral PU in a supine patient. Using a novel three‐dimensional anatomically realistic finite element modelling framework, we have compared performances of three dressing designs: (a) The Mepilex Border Sacrum (MBS) multilayer anisotropic silicone foam dressing (Mölnlycke Health Care), (b) an isotropic stiff dressing, and (c) an isotropic flexible dressing. Using our newly developed protective efficacy index (PEI) and aggravation index (AI) for assessing prophylactic and treatment dressings, we identified the anisotropic stiffness feature of the MBS dressing as a key design element.     

Surgical treatment and strategy in patients with multiple pressure sores

Pressure sores remain a common health problem, particularly among the physically limited or bedridden elderly, and can cause significant morbidity and mortality. This study aimed to present our surgical treatment and strategy for patients with multiple pressure sores. Between January 2010 and December 2016, 18 patients were enrolled. After adequate debridement, pressure sores were managed based on our treatment protocol. Patients'' age, aetiology, defect size and location, flap reconstruction, outcome, and follow‐up period were reviewed. A total of 10 men and 8 women (average age, 82.3 years) with a mean follow‐up period of 28.3 months (6‐72 months) were included. The mean defect area was 63.7 cm². The most common aetiology of the bedridden state was cerebrovascular accident (38.89%), and the most frequent sores were trochanteric pressure sores (53.57%). The average operative time and blood loss were 105.5 minutes and 100.8 mL, respectively. No haemodynamic variation or blood transfusion was noted during the surgery. The complication rate for each sore was 10.7%, including late recurrence. In conclusion, treating pressure ulcers requires careful patient education, intensive multidisciplinary optimisation, and meticulous wound care, and our treatment protocol ensures a shorter surgery time, less bleeding, and low complication rate.     

Negative pressure wound therapy in spinal fusion patients

Post‐operative wound complications are some of the most common acute complications following spine surgery. These surgical site infections (SSI) contribute to increased healthcare related costs. Negative pressure wound therapy (NPWT) has long been used for treatment of soft tissue injury or defects. NPWT may reduce the incident of SSI following spinal fusion procedures; however, its potential applications need further clarification. Thus, we conducted a retrospective analysis of two cohorts to compare NPWT to traditional sterile dressings following spinal fusions in regards to post‐operative outcomes. Following institutional review board approval, 42 patients who had a NPWT were matched by type of surgery to 42 patients who had traditional dressings. A retrospective chart‐review was completed. Outcome measures, particularly SSI and need for reoperation, were analyzed using one‐way ANOVA for both univariate and multivariate analysis. When controlled for sex and body‐mass index, the use of a NPWT was independently correlated with decreased SSI (P = .035). Superficial dehiscence, seroma, need for additional outpatient care, and need for operative revision were all found to occur at higher rates in the traditional dressing cohort. Closed incisional negative pressure wound therapy provides a cost‐effective method of decreasing surgical site infection for posterior elective spine surgeries.     

The sorptivity and durability of gelling fibre dressings tested in a simulated sacral pressure ulcer system

Wound‐dressing performances are affected by exudate viscosity, resistance to flow because of gravity, and bodyweight loads, the level of which is related to the body position. Here, we focussed on two dressing properties: (a) Sorptivity—the ability of dressings to transfer exudate away from the wound bed by capillary action—and (b) Durability—the capacity of dressings to maintain their integrity over time and during their removal. Both properties are critically important for avoiding further tissue damage but require the development of new laboratory tests for their measurement. A computer‐controlled phantom of an exuding sacral pressure ulcer has therefore been developed and used to compare the performances of Exufiber (Mölnlycke Health Care) vs an alternative market‐leading dressing. Sorptivity was determined using weight tests, and durability was measured through tensile tests of the used dressings. For a supine configuration, the Exufiber dressing demonstrated ~three times higher sorptivity and better durability, withstanding ~five times greater strain energy than the other product before failure occurred. This work paves the way for quantitative, standardised testing of dressings in all aspects of exudate management. The reported tests are further suitable for testing dressing combinations or how dressings interact with negative pressure wound therapy.     

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.     

Modelling the cost-effectiveness of subepidermal moisture measurement as part of a process of assessment and intervention to prevent hospital-acquired pressure ulcers

Skin tissue assessment is traditionally used to identify early signs of pressure damage from changes observed at the skin surface. However, the early onset of tissue damage induced by pressure and shear forces is likely to be on soft tissues beneath the surface of the skin. Subepidermal moisture (SEM) is a biophysical marker for the detection of early and deep pressure-induced tissue damage. Measurement of SEM can detect early pressure ulcers up to 5 days before visible skin changes occur. The aim of this study was to evaluate the cost-effectiveness of SEM measurement compared with visual skin assessment (VSA). A decision-tree model was developed. Outcomes are the incidence of hospital-acquired pressure ulcers, quality-adjusted life-years (QALYs) and costs to the UK National Health Service. Costs are at 2020/21 prices. The effects of parameter uncertainty are tested in univariate and probabilistic sensitivity analysis. In a representative NHS acute hospital, the incremental cost of SEM assessment as an adjunct to VSA is −£8.99 per admission, and SEM assessment is expected to reduce the incidence of hospital-acquired pressure ulcers by 21.1%, reduce NHS costs and lead to a gain of 3.634 QALYs. The probability of cost-effectiveness at a threshold of £30 000 per quality-adjusted life year is 61.84%. Pathways that include SEM assessment make it possible to implement early and anatomy-specific interventions which have the potential to improve the effectiveness of pressure ulcer prevention and reduce healthcare costs.     

A bioreactor for studying negative pressure wound therapy on skin grafts

Negative pressure wound therapy (NPWT) has become the prevailing standard of care for treating complex soft tissue wounds and is now being considered for use in alternative applications including improving skin graft take. While it is generally agreed that negative pressure leads to improved wound healing, universal consensus on its optimal application is not supported in the literature. We describe the design and validation of a bioreactor to determine the prospective benefits of NPWT on skin grafts and engineered skin substitutes (ESS). Clinically relevant pressures were applied, and the native human skin was able to withstand greater negative pressures than the engineered substitutes. Both skin types were cultured under static, flow‐only, and −75 mm Hg conditions for 3 days. While it remained intact, there was damage to the epidermal‐dermal junction in the ESS after application of negative pressure. The normal skin remained viable under all culture conditions. The engineered skin underwent apoptosis in the flow‐only group; however, the application of negative pressure reduced apoptosis. Vascular endothelial growth factor levels were significantly higher in the normal flow‐only group, 152.0 ± 75.1 pg/mg protein, than the other culture conditions, 81.6 ± 35.5 pg/mg for the static and 103.6 ± pg/mg for the negative pressure conditions. The engineered skin had a similar trend but the differences were not significant. This bioreactor design can be used to evaluate the impacts of NPWT on the anatomy and physiology of skin to improve outcomes in wounds after grafting with normal or engineered skin.     

Effects of loading and prophylactic dressings on the sacral and heel skin: An exploratory cross‐over trial

Pressure ulcers/injuries are caused by sustained loading and deformation of skin and underlying soft tissues. Prophylactic dressings are recommended as an adjunct to other preventive measures such as repositioning and offloading. The aim of this study was to investigate the effects of prophylactic soft silicone multi‐layered foam dressings on the skin structure and function of the two most common pressure areas, sacrum and heel, with and without loading. An exploratory randomised cross‐over trial using intra‐individual comparisons was conducted. Eight healthy volunteers (mean age 27.5 years) were assigned to three groups and either spent 2.5 hours on a standard hospital mattress lying in supine position with and without dressings or spent 2.5 hours with dressings applied but without loading. Skin temperature, stratum corneum, and epidermal hydration increased in all groups irrespective of wearing a dressing and/or loading. Mean roughness decreased at the heels. Reactive hyperaemia and the release of interleukin 1 alpha were associated with loading only. Results suggest that the occlusive effects of dressings are similar or only slightly greater than those observed with non‐loading or loading without dressings. Thus, a dressing does not cause additional irritation or skin changes during loading but it may reduce the inflammatory response.     

Systematic review: Incidence and prevalence of mucous membrane pressure injury in adults admitted to acute hospital settings

Mucous membrane pressure injury (MMPI) is associated with a history of medical device use at the site of injury. The current international guideline recommends they should be reported in incidence and prevalence studies. The aim of this systematic review was to analyse the incidence and prevalence of hospital‐acquired MMPI in adults admitted to acute hospital settings. Database searches (EBSCO CINAHL Complete, EBSCO Medline Complete, Embase, Scopus and Web of Science) were undertaken between October 2019 and February 2021, using search terms related to hospital‐acquired, mucosal and device‐related pressure injury/ulcer incidence and prevalence. Searches were limited to the English language. Articles published between 2008 and 2020, reporting incidence or prevalence of mucous membrane or medical device‐related pressure injury in non‐interventional samples were selected. Two authors assessed study bias and extracted data, with a third reviewer as arbitrator. Twenty‐one studies met inclusion criteria; most provided incidence data. No studies were found that specifically reported MMPI incidence or prevalence. It was possible to calculate incidence or prevalence from four studies; all were in intensive care settings. MMPI incidence of 0.8% and 30.4%, and prevalence of 1.7% and 3.7% were found. One study provided data that enabled calculation of prevalence of 0.1% in a non‐intensive care sample. Only one other study provided specific data about MMPI. It is concluded that there is insufficient evidence available to enable estimation of MMPI incidence or prevalence in either acute hospital or intensive care settings.     

Utilization of a topical autologous blood clot for treatment of pressure ulcers

Management and treatment of pressure ulcers (PUs) are met with great difficulty due to various factors that cause vulnerability of the soft tissue such as location, limited mobility, increased friction and shearing forces, as well as other comorbidities that may delay or halt wound healing. The topical autologous blood clot therapy (TABCT) is a point-of-care treatment used as a blood clot to assist in recreating and repairing the extracellular matrix (ECM). The mechanism of action consists of reconstruction of the ECM by incorporating into the ulcer, providing protection from further external destruction, while assisting in advancement through the wound healing phases via interaction of necessary growth factors, mediators, and chemokines. This study aims to assess the efficacy of the TABCT in the treatment of PUs in comparison to standard of care (SOC) treatment. Twenty-four patients, 18 years or older, with PUs ranging from stage 1 to 4, were included in this study. TABCT was created by using the patient's own peripheral blood in a point of care setting. Efficacy in percent area reduction (PAR) on weeks 4 and 12 with TABCT over SOC was assessed. Treatment using TABCT in PUs resulted in 77.9% of the patients achieving a 50% PAR on week 4. The mean PAR on week 12 was 96.23% with 45% of the wounds treated with TABCT achieving complete wound closure. TABCT exhibited efficacy in PAR of PUs. In addition, TABCT use prompted granulation tissue formation over vital structures, such as bone, which is often present in later stage PUs. The potential of bringing an affordable, cost-effective, advanced biologic bedside treatment that is efficacious in resolution of these complex wounds has the potential to drastically reduce the burden of treatment on the health system.     

Cellular and molecular changes that predispose skin in chronic spinal cord injury to pressure ulcer formation

Patients with spinal cord injury have a predisposition to develop pressure ulcers. Specific characteristics of the patients'' skin potentially involved have not yet been identified. The purpose of this investigation was to determine whether loss of neuronal control affects cellular and molecular homeostasis in the skin. Intact afflicted skin, wound edge of pressure ulcers, and control skin were analysed. Platelets, transforming growth factor‐β1, and activin A were identified by immunohistochemistry. Transforming growth factor‐β‐like activity was determined by bioassay, and gene expression by DNA microarray analysis or RT‐PCR. In afflicted skin, enhanced platelet extravasation was detected. Transforming growth factor‐β1 and activin A accumulated in the dermal‐epidermal junction zone. Transforming growth factor‐β‐like activity and activin A expression were increased in intact afflicted skin (compared to control skin) and were further enhanced in pressure ulcers. In vitro, activity was generated by fibroblast‐epithelial cell interactions, which also induced activin A. Thus, loss of neuronal control in spinal cord injury appears to trigger inappropriate wound healing processes in the patients'' skin. Plasma leakage and increased transforming growth factor‐β‐like activity combined with shear forces potentially enhance the risk for pressure ulcer formation.