Pressure Induced Deep Tissue Injury Explained

Decreased proteasome function increases oxidative stress in the early stage of pressure ulcer development

The aging process in the elderly results in heightened skin fragility associated with various disorders, including pressure ulcers (PUs). Despite the high incidence of PUs in the elderly population, there is a limited body of research specifically examining the impact of aging on the development of pressure ulcers. Therefore, investigating age-related physiological abnormalities is essential to elucidate the pathogenesis of PUs. Ischemia-reperfusion (I/R) injury and the subsequent oxidative stress caused by reactive oxygen species (ROS) play essential roles in the early stage of PUs. In this study, we used a mouse model of proteasomal dysfunction with an age-related phenotype to examine the role of proteasome activity in cutaneous I/R injury in vivo. Decreased proteasome function did not affect the expression of inflammatory cytokines and adhesion molecules in the I/R area in transgenic mice; however, proteasome inhibition increased oxidative stress that was not attenuated by activation of the oxidative stress response mediated by NF-E2-related factor 2 (Nrf2). In dermal fibroblasts (FCs) subjected to hypoxia-reoxygenation (H/R), proteasome inhibition induced oxidative stress and ROS production, and Nrf2 activation did not adequately upregulate antioxidant enzyme expression, possibly leading to antioxidant/oxidant imbalance. The free radical scavenger edaravone had protective effects against I/R injury in vivo and decreased oxidative stress in FCs treated with a proteasome inhibitor and subjected to H/R in vitro. The results suggest that the age-related decline in proteasome activity promotes cutaneous I/R injury-induced oxidative stress, and free radical scavengers may exert protective effects by preventing oxidative stress in the early stage of PUs.

Smart seat cushion feasibility pilot study: automated interface pressure modulation of individuals with spinal cord Injury

This study investigates the functionality and feasibility of a novel smart seat cushion system designed for wheelchair users with spinal cord injuries. The cushion, equipped with air cells that serve as both sensors and actuators, was tested on 24 participants for its real-time pressure mapping, automated pressure redistribution, and pressure offloading functions. A commercial pressure mat was concurrently used to validate the cushion's pressure modulation functions. Additionally, the perceived comfort of the cushion was evaluated using General Discomfort Assessment (GDA) and Discomfort Intensity (DIS) scores, which provided insights into participants' overall comfort and discomfort levels. Real-time pressure profiles generated by the cushion resembled commercial pressure mat readings. During tests with individuals with spinal cord injury, the cushion was able to dynamically generate and display the real-time pressure profile of a seated individual with strong precision (correlation to commercial pressure mat: r ranging from 0.76 to 0.88), providing effective input into pressure modulation functions. Pressure redistribution algorithms eliminated peak pressure and reduced the overall pressure at the interface. Pressure offloading algorithms automatically identified the regions with the highest interface pressure and subsequently relieved the pressure from those areas. User feedback showed that the cushion was comfortable after redistribution and offloading. This work demonstrated the feasibility of an advanced smart seat cushion system for wheelchair users with spinal cord injuries. The cushion was capable of redistributing pressure evenly across the seating surface, ensuring user's comfort. Additionally, it identifies and eliminates high-pressure points, further improving comfort and reducing the risk of pressure injuries.

Risk Factors of Intraoperative Pressure Injury in Adult Patients Undergoing Neurologic Surgery

GENERAL PURPOSE

To present research investigating the incidence of and risk factors associated with intraoperative pressure injury in patients undergoing neurologic surgery at Xiangya Hospital, Central South University in China.

TARGET AUDIENCE

This continuing education activity is intended for physicians, physician assistants, nurse practitioners, and registered nurses with an interest in skin and wound care.

LEARNING OBJECTIVES/OUTCOMES

After participating in this educational activity, the participant will:1. Identify the incidence of intraoperative pressure injuries (PIs) in patients undergoing neurologic surgery at Xiangya Hospital, Central South University in China.2. Describe risk factors for intraoperative PI.3. Outline strategies to help mitigate intraoperative PI risk.

User opinions about connected pressure detection systems to prevent wheelchair-related pressure injuries: an exploratory cross-sectional survey

About 1% of the world's population uses a wheelchair. Wheelchair use is a well-known risk of pressure injury. A connected pressure detection system could help to prevent this complication that is linked to long durations of sitting, provided that user expectations are understood. The aim of this study was to explore the needs of wheelchair users (WU) regarding connected pressure detection systems to prevent pressure injury. A cross-section survey-based study of WU was conducted, using an anonymous electronic questionnaire posted from July 2019 to June 2020. Eighty-eight people responded. The majority were power wheelchair users (72.7%); one third (33.0%) had already sustained a pressure injury; only 17.0% knew of the existence of pressure detection systems, nevertheless 78.4% believed that they could be useful in daily life. The feature that received the highest rating was a pressure warning alarm (4.2/5 points). The majority (71.6%) preferred reminder-alerts to be set according to their habits and not according to medical guidelines. In conclusion, pressure detecting systems were perceived as useful to prevent pressure injuries by both manual and power wheelchair users. Work is needed to inform potential users of the existence of such systems.

An ex vivo animal model to study the effect of transverse mechanical loading on skeletal muscle

In many populations like wheelchair and prosthetic users, the soft tissue is subject to excessive or repetitive loading, making it prone to Deep Tissue Injury (DTI). To study the skeletal muscle response to physical stress, numerous in vitro and in vivo models exist. Yet, accuracy, variability, and ethical considerations pose significant trade-offs. Here, we present an ex vivo approach to address these limitations and offer additional quantitative information on cellular damage. In this study, skeletal muscle tissue from Sprague Dawley rats was isolated and transversely loaded. Histological analysis and fluorescence staining demonstrated that the setup was suitable to keep the tissue alive throughout the experimental procedure. Mechanically induced cell damage was readily distinguishable through morphological changes and uptake of a membrane impermeable dye. Our comparably simple experimental setup can be adapted to different loading conditions and tissues to assess the cell response to mechanical loading in future studies.

The effect of prolonged 60° head of bed elevation on sacral subepidermal oedema in healthy adults: A quantitative prospective exploratory study

Head of bed elevation is used to manage some medical and surgical conditions however this may increase a patient's risk of sacral pressure injuries. Novel point-of-care technologies that measure subepidermal moisture can identify changes in localised subepidermal oedema and potential pressure injury risk. This prospective exploratory study investigated variations in sacral subepidermal oedema in healthy adults during 120-min of 60° head of bed elevation. Sacral subepidermal oedema was measured at 20-min intervals using the Provisio® subepidermal moisture scanner. Descriptive analysis, one-way repeated measures analysis of variance and an independent t-test were conducted. Slightly more male volunteers (n = 11; 55%) were recruited and the sample mean age was 39.3 years (SD 14.7) with an average body mass index of 25.8 (SD 4.3). Little variation in the mean sacral subepidermal moisture of healthy adults was observed. There was a statistically significant difference in the mean sacral subepidermal moisture measurements between males and females (Mean difference 0.18; 95% confidence intervals: 0.02 to 0.35; P = .03). Healthy adults can tolerate prolonged 60° head of bed elevation without developing increased subepidermal sacral oedema. This warrants further investigation in other populations, in various positions and over different time periods.

Validation of a sub-epidermal moisture scanner for early detection of pressure ulcers in an ex vivo porcine model of localized oedema

Pressure ulcers (PUs) remain a chronic health problem with severe impacts on healthcare systems. Early detection is crucial to providing effective interventions. However, detecting PUs currently relies on subjective tissue evaluations, such as visual skin assessment, precluding interventions prior to the development of visible tissue damage. There is an unmet need for solutions that can detect early tissue damage before visual and tactile signs occur. Assessments based on sub-epidermal moisture (SEM) measurements represent an opportunity for robust and objective early detection of PUs, preventing broken skin PUs in more high-risk patients at high-risk anatomical locations. While SEM assessment technology has been validated in computational, bench and tissue phantom models, validation in soft tissue was absent. In this study, we successfully validated the ability of a commercially available SEM assessment device to measure and detect sub-epidermal moisture changes in a novel ex vivo porcine soft tissue model of localised oedema. When controlled and incremental fluid volumes (Phosphate Buffer Solution) were injected into porcine soft tissues, statistically significant differences were found in SEM values between fluid-injected sites, representing an inflammatory oedematous condition, and healthy tissue control sites, as measured by the SEM device. The device provided reproducible readings by detecting localised oedema changes in soft tissues, reflecting the build-up of fluid as small as 1 ml into the underlying tissue. Spatial characterization experiments described the ability of the device technology to differentiate between healthy and oedematous tissue. Our findings validate the use of SEM assessment technology to measure and quantify localized oedema.

Guarding skin under PPE: Mechanistic insights and technological innovations

In the presence of diseases transmitted through respiratory droplets and direct contact, healthcare workers (HCWs) necessitate the use of personal protective equipment (PPE). For optimal safety, PPE should securely conform to the skin during extended wear. However, conventional PPE often lacks adequate air permeability and hygroscopicity, trapping heat and moisture emitted by the body within the enclosure. Such a hot and humid internal environment can induce skin damage, such as erythema, rash, pruritus, and itching among others, leading to microbial growth on the skin surface, the production of inflammatory mediators at the wound site and an increased risk of infection. This review strives to comprehensively elucidate the fundamental mechanisms triggering adverse skin reactions and their resultant manifestations. Furthermore, we explore recent advancements aimed at inhibiting these mechanisms to effectively mitigate the occurrence of skin lesions.

Functional non-uniformity of periodontal ligaments tunes mechanobiological stimuli across soft- and hard-tissue interfaces

The bone-periodontal ligament-tooth (BPT) complex is a unique mechanosensing soft-/hard-tissue interface, which governs the most rapid bony homeostasis in the body responding to external loadings. While the correlation between such loading and alveolar bone remodelling has been widely recognised, it has remained challenging to investigate the transmitted mechanobiological stimuli across such embedded soft-/hard-tissue interfaces of the BPT complex. Here, we propose a framework combining three distinct bioengineering techniques (i, ii, and iii below) to elucidate the innate functional non-uniformity of the PDL in tuning mechanical stimuli to the surrounding alveolar bone. The biphasic PDL mechanical properties measured via nanoindentation, namely the elastic moduli of fibres and ground substance at the sub-tissue level (i), were used as the input parameters in an image-based constitutive modelling framework for finite element simulation (ii). In tandem with U-net deep learning, the Gaussian mixture method enabled the comparison of 5195 possible pseudo-microstructures versus the innate non-uniformity of the PDL (iii). We found that the balance between hydrostatic pressure in PDL and the strain energy in the alveolar bone was maintained within a specific physiological range. The innate PDL microstructure ensures the transduction of favourable mechanobiological stimuli, thereby governing alveolar bone homeostasis. Our outcomes expand current knowledge of the PDL's mechanobiological roles and the proposed framework can be adopted to a broad range of similar soft-/hard- tissue interfaces, which may impact future tissue engineering, regenerative medicine, and evaluating therapeutic strategies. STATEMENT OF SIGNIFICANCE: A combination of cutting-edge technologies, including dynamic nanomechanical testing, high-resolution image-based modelling and machine learning facilitated computing, was used to elucidate the association between the microstructural non-uniformity and biomechanical competence of periodontal ligaments (PDLs). The innate PDL fibre network regulates mechanobiological stimuli, which govern alveolar bone remodelling, in different tissues across the bone-PDL-tooth (BPT) interfaces. These mechanobiological stimuli within the BPT are tuned within a physiological range by the non-uniform microstructure of PDLs, ensuring functional tissue homeostasis. The proposed framework in this study is also applicable for investigating the structure-function relationship in broader types of fibrous soft-/hard- tissue interfaces.

The theory and practice of pressure ulcer/injury risk assessment: a critical discussion

Pressure ulcer/injury (PU) risk assessment is widely considered an essential component in clinical practice. It is a complex and broad concept that includes different approaches, such as clinical judgement, using standardised risk assessment instruments, skin assessments, or using devices to measure skin or tissue properties. A distinction between PU risk assessment and early detection is important. PU risk measures the individual's susceptibility to developing a PU under a specific exposure (primary prevention), and early detection includes the assessment of early (sub)clinical signs and symptoms to prevent progression and to support healing (secondary prevention). PU risk is measured using prognostic/risk factors or prognostic models. Every risk estimate is a probability statement containing varying degrees of uncertainty. It therefore follows that every clinical decision based on risk estimates also contains uncertainty. PU risk assessment and prevention is a complex intervention, where delivery contains several interacting components. There is a huge body of evidence indicating that risk assessment and its outcomes, the selection of preventive interventions and PU incidence are not well connected. Methods for prognostic model development and testing in PU risk research must be improved and follow state-of-the-art methodological standards. Despite these challenges, we do have substantial knowledge about PU risk factors that helps us to make better clinical decisions. An important next step in the development of PU risk prediction might be the combination of clinical and other predictors for more individualised care. Any prognostic test or procedure must lead to better prevention at an acceptable cost.

Studying mechanical load at body-seat interface during dynamic activities such as wheelchair propulsion: a scoping review

BACKGROUND

The increasing number of wheelchair users and their risk of medical complications such as pressure ulcers (PU) make it important to have a better understanding of their seating characteristics. However, while most studies tackling this issue are based on static measurements, wheelchair users are active in their wheelchairs when performing daily life activities. This suggests the need to assess the mechanical loads at the wheelchair user's body-seat interface during dynamic activities.

OBJECTIVES

A scoping review was conducted to explore the existing data (shear load and pressure) and highlight significant parameters, relevant conditions and methodological strategies when studying wheelchair users performing a dynamic task.

MATERIALS AND METHODS

The literature search was performed by applying the PRISMA methodology.

RESULTS

A total of 11 articles met the inclusion criteria. Differences between static and dynamic data were found in the literature for peak pressure values, pressure distribution and the location of peak pressure. None measured tangential load at the seat/body interface, although two studies measured the shift of the ischial region. A significant impact of the type of pathology has been quantified, showing the need to perform experimental studies on diverse populations. The protocol and the pressure parameters studied were very diverse.

CONCLUSION

Further studies carefully choosing interface pressure mapping parameters and investigating a broader range of pathologies are required. Additionally, researchers should focus on finding a way to measure seated tangential load.

A pressure monitoring approach for pressure ulcer prevention

BACKGROUND

A pressure ulcer (PU) is a debilitating condition that disproportionately affects people with impaired mobility. PUs facilitate tissue damage due to prolonged unrelieved pressure, degrading quality of life with a considerable socio-economic impact. While rapid treatment is crucial, an effective  prevention strategy may help avoid the development of PUs altogether. While pressure monitoring is currently used in PU prevention, available monitoring approaches are not formalised and do not appropriately account for accumulation and relief of the effect of an applied pressure over a prolonged duration. The aim of this study was to define an approach that incorporates the accumulation and relief of an applied load to enable continuous pressure monitoring.

RESULTS

A tunable continuous pressure magnitude and duration monitoring approach that can account for accumulated damaging effect of an applied pressure and pressure relief over a prolonged period is proposed. Unlike classic pressure monitoring approaches, the presented method provides ongoing indication of the net impact of a load during and after loading.

CONCLUSIONS

The tunable continuous pressure magnitude and duration monitoring approach proposed here may further development towards formalised pressure monitoring approaches that aim to provide information on the risk of PU formation in real-time.

Definition and evaluation of a finite element model of the human heel for diabetic foot ulcer prevention under shearing loads

Diabetic foot ulcers are triggered by mechanical loadings applied to the surface of the plantar skin. Strain is considered to play a crucial role in relation to ulcer etiology and can be assessed by Finite Element (FE) modeling. A difficulty in the generation of these models is the choice of the soft tissue material properties. In the literature, many studies attempt to model the behavior of the heel soft tissues by implementing constitutive laws that can differ significantly in terms of mechanical response. Moreover, current FE models lack of proper evaluation techniques that could estimate their ability to simulate realistic strains. In this article, we propose and evaluate a FE model of the human heel for diabetic foot ulcer prevention. Soft tissue constitutive laws are defined through the fitting of experimental stretch-stress curves published in the literature. The model is then evaluated through Digital Volume Correlation (DVC) based on non-rigid 3D Magnetic Resonance Image Registration. The results from FE analysis and DVC show similar strain locations in the fat pad and strain intensities according to the type of applied loads. For additional comparisons, different sets of constitutive models published in the literature are applied into the proposed FE mesh and simulated with the same boundary conditions. In this case, the results in terms of strains show great diversity in locations and intensities, suggesting that more research should be developed to gain insight into the mechanical properties of these tissues.

Identifiability of soft tissue constitutive parameters from in-vivo macro-indentation

Reliable identification of soft tissue material parameters is frequently required in a variety of applications, particularly for biomechanical simulations using finite element analysis (FEA). However, determining representative constitutive laws and material parameters is challenging and often comprises a bottleneck that hinders the successful implementation of FEA. Soft tissues exhibit a nonlinear response and are commonly modeled using hyperelastic constitutive laws. In-vivo material parameter identification, for which standard mechanical tests (e.g., uniaxial tension and compression) are inapplicable, is commonly achieved using finite macro-indentation test. Due to the lack of analytical solutions, the parameters are commonly identified using inverse FEA (iFEA), in which simulated results and experimental data are iteratively compared. However, determining what data must be collected to accurately identify a unique parameter set remains unclear. This work investigates the sensitivities of two types of measurements: indentation force-depth data (e.g., measured using an instrumented indenter) and full-field surface displacements (e.g., using digital image correlation). To eliminate model fidelity and measurement-related errors, we employed an axisymmetric indentation FE model to produce synthetic data for four 2-parameter hyperelastic constitutive laws: compressible Neo-Hookean, and nearly incompressible Mooney-Rivlin, Ogden, and Ogden-Moerman models. For each constitutive law, we computed the objective functions representing the discrepancies in the reaction force, the surface displacement, and their combination, and visualized them for hundreds of parameter sets, spanning a representative range as found in the literature for the bulk soft tissue complex in human lower limbs. Moreover, we quantified three identifiability metrics, which provided insights into the uniqueness (or lack thereof) and the sensitivities. This approach provides a clear and systematic evaluation of the parameter identifiability, which is independent of the selection of the optimization algorithm and initial guesses required in iFEA. Our analysis indicated that the indenter's force-depth data, despite being commonly used for parameter identification, was insufficient for reliably and accurately identifying both parameters for all the investigated material models and that the surface displacement data improved the parameter identifiability in all cases, although the Mooney-Rivlin parameters remained poorly identifiable. Informed by the results, we then discuss several identification strategies for each constitutive model. Finally, we openly provide the codes used in this study, to allow others to further investigate the indentation problem according to their specifications (e.g., by modifying the geometries, dimensions, mesh, material models, boundary conditions, contact parameters, or objective functions).

Variations in sacral oedema levels over continuous 60-degree head of bed elevation positioning in healthy adults: An observational study

BACKGROUND

Subepidermal moisture (SEM) scanning is a novel technology that measures changes in localised oedema. Accumulation of subepidermal oedema is associated with early tissue damage that may lead to a pressure injury.

AIM

The primary study objective was to observe the variations in sacral subepidermal oedema levels over a continuous period of 60-degree head of bed elevation positioning.

METHODS

Healthy adult participants were recruited in this prospective observational study. Participants were positioned at 60-degree head of bed elevation for 120 min and sacral SEM measurements were collected at baseline and in 20 min increments.

RESULTS

A total of 20 participants with a mean age of 39.3 years (SD = 14.7) were recruited. The mean SEM delta value increased 6.3% from 0.46 SEM delta at baseline to 0.49 SEM delta after 120 min, however these differences are not statistically significant (p = .21). There were also no significant findings between SEM delta variations and demographic factors.

CONCLUSION

In a sample of healthy individuals, 120 min of continuous loading with a 60-degree head of bed elevation did not lead to a significant change in sacral subepidermal oedema levels. Further research on the response of healthy adult tissue under external forces associated with different angles of head of bed positioning may further contribute to our understanding pressure injury prevention.

The Effects of Skin Temperature Changes on the Integrity of Skin Tissue: A Systematic Review

OBJECTIVE

To determine whether changes in skin temperature can affect the integrity of skin.

METHODOLOGY

The authors conducted a systematic literature search as per the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. They searched the CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane, MEDLINE Complete, Academic Search Ultimate, and HyDi databases for articles examining the effects of skin temperature on skin integrity published through April 2020. Two independent reviewers scored the methodologic quality of the 13 included studies.

RESULTS

Only 11 studies were included in the qualitative analysis, as the other two articles had a critical risk of bias. There is strong evidence to indicate that an increase in skin temperature leads to changes in skin structure and function. However, ulcer formation was more affected by intrinsic and extrinsic factors, rather than by temperature alone.

CONCLUSION

Further high-quality randomized controlled trials are required to investigate the direct effect of skin temperature on ulceration.

Mechanical analysis of deep tissue injury during sitting in patients with spinal cord injury via parametric finite element model

Spinal cord injury patients are prone to develop deep tissue injury because of long-term mechanical load. However, there is a lack of statistical research on the influence of tissue characteristics on the internal mechanical state of soft tissue. This study aimed to investigate the influence of tissue characteristics on the internal mechanical state of buttock in spinal cord injury patients. A three-dimensional reference buttock model was established and a visualization program was generated to modify the parameter values. Through changing the muscle atrophy, body mass index and the radius of curvature of the ischial tuberosity, 96 different model variants were simulated and validated in this study. With body mass index increasing from 16 to 40, the principal shear stress was 10.4 times principal compressive stress, the maximum shear strain and the max cluster volume increased by 1.2 (P < 0.001) and 8.8 times (P < 0.001), respectively. The interaction between BMI and muscle atrophy was significant when BMI was greater than or equal to 22.5 kg/m². In all BMI stages, when the radius of curvature of the ischial tuberosity was 19 mm, the internal stress of the tissue always occupies the highest value. The results demonstrate that body mass index is the most important factor affecting the risk of buttock deep tissue injury. This study provides insights into investigation of inter-individual factors influencing the soft tissue response and assessment of deep tissue injury risk during sitting.

Measuring subepidermal moisture to detect early pressure ulcer development: a systematic review

OBJECTIVE

The aim was to assess evidence related to the measuring of subepidermal moisture (SEM) to detect early, nonvisible development of pressure ulcers (PUs).

METHOD

Using systematic review methodology, all quantitative animal and human research studies written in English were considered. In January 2021, PubMed, CINAHL, SCOPUS, Cochrane and EMBASE databases were searched. The primary outcome of interest was the validity of SEM measurement to detect early PU development. The secondary outcome was time to PU detection, sensitivity and specificity of SEM measurement, and the impact of SEM measurements on PU prevention. Data analysis was undertaken using RevMan and narrative synthesis.

RESULTS

A total of 17 articles met the inclusion criteria. In all studies, a consistent abnormal deviation in SEM measurements corresponded with evidence of visual PU development. Time to PU development, explored in four studies, showed earlier detection of PU development using SEM measurement. RevMan analysis identified the mean difference in time to PU development (SEM measurement versus visual skin assessment, VSA) was 4.61 days (95% confidence interval: 3.94-5.28; p=0.0001) in favour of SEM measurements. The sensitivity of SEM measurements was reported in four studies, and scores varied from 48.3% to 100.0%. Specificity was also reported in four studies and scores ranged from 24.4% to 83.0%. The impact of the detection of abnormal SEM measurements on PU prevention was explored by one study. Results showed a 93% decrease in PU rates when staff acted on the results of the SEM readings.

CONCLUSION

The findings of this review identified that SEM measurement detects PU development earlier than VSA. Furthermore, when staff responded to abnormal SEM measurements, prevention strategies were enhanced, with a subsequent reduction in visible PU development. SEM measurement may therefore be a useful addition to PU prevention strategies.

DECLARATION OF INTEREST

The School of Nursing & Midwifery, RCSI has a research agreement with Bruin Biometrics. Funding for the study was through an Irish Research Council PhD Enterprise Partnership Scheme with Bruin Biometrics. The authors have no other conflicts of interest.

Newborn and elderly skin: two fragile skins at higher risk of pressure injury

Skin is a key organ maintaining internal homeostasis by performing many functions such as water loss prevention, body temperature regulation and protection from noxious substance absorption, microorganism intrusion and physical trauma. Skin ageing has been well studied and it is well known that physiological changes in the elderly result in higher skin fragility favouring the onset of skin diseases. For example, prolonged and/or high-intensity pressure may suppress local blood flow more easily, disturbing cell metabolism and inducing pressure injury (PI) formation. Pressure injuries (PIs) represent a significant problem worldwide and their prevalence remains too high. A higher PI prevalence is correlated with an elderly population. Newborn skin evolution has been less studied, but some data also report a higher PI prevalence in this population compared to older children, and several authors also consider this skin as physiologically fragile. In this review, we compare the characteristics of newborn and elderly skin in order to determine common features that may explain their fragility, especially regarding PI risk. We show that, despite differences in appearance, they share many common features leading to higher fragility to shear and pressure forces, not only at the structural level but also at the cellular and molecular level and in terms of physiology. Both newborn and elderly skin have: (i) a thinner epidermis; (ii) a thinner dermis containing a less-resistant collagen network, a higher collagen III:collagen I ratio and less elastin; (iii) a flatter dermal-epidermal junction (DEJ) with lower anchoring systems; and (iv) a thinner hypodermis, resulting in lower mechanical resistance to skin damage when pressure or shear forces are applied. At the molecular level, reduced expression of transforming growth factor β (TGFβ) and its receptor TGFβ receptor II (TβRII) is involved in the decreased production and/or increased degradation of various dermal extracellular matrix (ECM) components. Epidermal fragility also involves a higher skin pH which decreases the activity of key enzymes inducing ceramide deficiency and reduced barrier protection. This seems to be correlated with higher PI prevalence in some situations. Some data also suggest that stratum corneum (SC) dryness, which may disturb cell metabolism, also increases the risk of PI formation. Besides this structural fragility, several skin functions are also less efficient. Low applied pressures induce skin vessel vasodilation via a mechanism called pressure-induced vasodilation (PIV). Individuals lacking a normal PIV response show an early decrease in cutaneous blood flow in response to the application of very low pressures, reflecting vascular fragility of the skin that increases the risk of ulceration. Due to changes in endothelial function, skin PIV ability decreases during skin ageing, putting it at higher risk of PI formation. In newborns, some data lead us to hypothesize that the nitric oxide (NO) pathway is not fully functional at birth, which may partly explain the higher risk of PI formation in newborns. In the elderly, a lower PIV ability results from impaired functionality of skin innervation, in particular that of C-fibres which are involved in both touch and pain sensation and the PIV mechanism. In newborns, skin sensitivity differs from adults due to nerve system immaturity, but the role of this in PIV remains to be determined.

Risk factors for the development and evolution of deep tissue injuries: A systematic review

AIMS

The aim of this systematic review is to identify the current epidemiological evidence indicating the unique risk factors for deep tissue injury (DTI) compared to grade I-IV pressure injury (PI), the proportion of DTI which evolve rather than resolve and the anatomical distribution of DTI.

METHODS

A systematic literature search was undertaken using the MEDLINE and CINAHL Plus databases using the search terms 'Deep tissue injury OR DTI [Title/abstract]'. A google scholar search was also conducted in addition to hand searches of relevant journals, websites and books which were identified from reference lists in retrieved articles. Only peer-reviewed English language articles published 2009-2021 were included, with full text available online.

RESULTS

The final qualitative analysis included nine articles. These included n = 4 retrospective studies, n = 4 prospective studies and n = 1 animal study.

CONCLUSION

The literature indicates that the majority of DTI occur at the heel and sacrum although in paediatric patients they are mainly associated with medical devices. Most DTI are reported to resolve, with between 9.3 and 27% deteriorating to full thickness tissue loss. Risk factors unique to DTI appear to include anaemia, vasopressor use, haemodialysis and nicotine use although it is unclear if these factors are unique to DTI or are shared with grade I-IV PI. Factors associated with deterioration include cooler skin measured using infrared thermography and negative capillary refill. With 100% of DTI showing positive capillary refill in one study resolving without tissue loss (p = 0.02) suggesting this may be an effective prognostic indicator. More prospective studies are required focusing on establishing causal links between risk factors identified in earlier retrospective studies. Ideally these should use statistically powered samples and sufficient follow up periods allowing DTI outcomes to be reached. Further work is also needed to establish reliable diagnostic criteria for DTI in addition to more studies in the paediatric population.

Effects of vasopressor agents on the development of pressure ulcers in critically ill patients: a systematic review

OBJECTIVE

The primary objective of this systematic review was to determine the effect of vasopressor agents on the development of pressure ulcers (PUs) among critically ill patients in intensive care units (ICUs). The secondary outcome of interest was length of stay in the ICU.

METHOD

A systematic review was undertaken using the databases searched: Medline, Embase, CINAHL and The Cochrane Library. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to formulate the review. Data were extracted using a predesigned data extraction table and analysed as appropriate using RevMan. Quality appraisal was undertaken using the EBL Critical Appraisal Tool.

RESULTS

The inclusion criteria were met by 13 studies. Two studies provided sufficient data to compare the number of patients who developed a PU with and without the use of vasopressors. Consistently, within these two studies, being treated with a vasopressor increased the likelihood of PU development. RevMan analysis identified that shorter duration of administration of vasopressors was associated with less PU development (mean difference (MD) 65.97 hours, 95% confidence interval (CI): 43.47-88.47; p=0.0001). Further, a lower dose of vasopressors was also associated with less PU development (MD: 8.76μg/min, 95% CI: 6.06-11.46; p<0.00001). Mean length of stay increased by 11.46 days for those with a PU compared to those without a PU (MD: 11.46 days; 95% CI: 7.10-15.82; p<0.00001). The overall validities of the studies varied between 45-90%, meaning that there is potential for bias within all the included studies.

CONCLUSION

Vasopressor agents can contribute to the development of PUs in critically ill patients in ICUs. Prolonged ICU stay was also associated with pressure ulcers in this specific patient group. Given the risk of bias within the included studies, further studies are needed to validate the findings of this review paper.

Sub-epidermal moisture versus traditional and visual skin assessments to assess pressure ulcer risk in surgery patients

OBJECTIVE

To compare the predictive ability of subepidermal moisture (SEM) measurement versus traditional risk assessment and visual skin assessment (VSA) as means of detecting early pressure ulcer (PU) damage development among adults undergoing surgery.

METHOD

A non-experimental, comparative, descriptive cohort study design was used. Following ethical approval, participants who had given their informed written consent had their skin assessed over the areas that were weight-bearing during surgery, using VSA and the SEM measurement. Visual PUs were graded according to the European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel ulcer grading system. Assessments took place preoperatively, then daily on the ward, beginning on day one postoperatively and continuing for three days or until discharge.

RESULTS

Of the 231 participants, who had a mean age of 57.50 years, 55.8% (n=129) were male. The most common comorbidity was cardiology/vascular (n=42; 18.2%). Just over half (52.4%; n=121) underwent orthopaedic surgery and 47.6% (n=110) underwent non-orthopaedic surgery; 70% (n=163) received a general anaesthetic and 43% (n=100) were in the supine decubitus position during surgery. PU incidence was 51% (n=116), according to SEM measurement, and 3% (n=7) according to VSA. Among the seven participants who developed a visual PU, 10 PUs at stage 1 developed (31%); some patients developed more than one PU. Of the participants who had assessments for three days postoperatively, 94% (n=61) had a persistently high SEM delta on day three. The variables that emerged as statistically significantly related to abnormal SEM measurement deltas among these participants were: surgery duration (p=0.038); having orthopaedic surgery (p=0.020); supine surgical position (p=0.003); spinal anaesthetic type (p=0.0001); and Waterlow and Braden mobility subscale day one postoperatively (p=0.0001). None of the variables had a statistically significant influence on abnormal VSA.

CONCLUSION

Surgical patients, because of immobility, are vulnerable to the action of compression and shear forces. These forces cause changes at a cellular level that trigger inflammation, which is a precursor to early tissue damage. SEM measurement can detect this tissue damage from the increase in the underlying tissue water content that results from inflammation. From the findings of this study, SEM measurement is very promising in the detection of early tissue damage in those at risk of PU development among the surgical population.

Pressure Injuries in Critical Care Patients in US Hospitals: Results of the International Pressure Ulcer Prevalence Survey

PURPOSE

The purpose of this secondary analysis was to examine pressure injury (PI) prevalence, PI risk factors, and prevention practices among adult critically ill patients in critical care units in the United States using the International Pressure Ulcer Prevalence™ (IPUP) Survey database from 2018 to 2019.

DESIGN

Observational, cohort study with cross-sectional data collection and retrospective data analysis.

SUBJECTS AND SETTING

The sample comprised 41,866 critical care patients drawn from a sample of 296,014 patients in US acute care facilities who participated in the 2018 and/or 2019 IPUP surveys. The mean age among critical care patients was 63.5 years (16.3) and 55% were male. All geographic regions of the United States were represented in this sample, with the greatest percentages from the Southeast (47.5%) and Midwest (17.5%) regions.

METHODS

Overall critical care PI prevalence and hospital-acquired PI (HAPI) rates were obtained and analyzed using the 2018/2019 IPUP survey database. Critical care PI risk factors included in the database were analyzed using frequency distributions. Prevention practices among critically ill patients were analyzed to evaluate differences in practices between patients with no PIs, superficial PIs (stage 1, stage 2), and severe PIs (stage 3, stage 4, unstageable, deep tissue pressure injury).

RESULTS

The overall PI prevalence for critical care patients was 14.3% (n = 5995) and the overall HAPI prevalence was 5.85% (n = 2451). In patients with severe HAPIs, the most common risk factors were diabetes mellitus (29.5%), mechanical ventilation (27.6%), and vasopressor agents (18.9%). Significant differences between patients with no PIs as compared to those with superficial or severe HAPIs (P = .000) for all prevention practices were found.

CONCLUSIONS

Study findings support the gaps elucidated in previous critical care studies on PI development in this population. The 2 most persistent gaps currently challenging critical care practitioners are (1) accurate risk quantification in this population and (2) the potential for unavoidability in PI development among critically ill patients.

The Effect of Padded Adhesive Dressing and Static Body Position on Sacral Interface Pressure

OBJECTIVES

Padded adhesive bandages are frequently used in the inpatient setting for sacral pressure injury prevention, but it is unclear whether they truly decrease interface pressure. We hypothesized such devices reduce sacral peak interface pressure in the supine position, which would be further reduced in 30-degree reclined and upright seated positions.

METHODS

Study participants rested with their sacrum on a pressure-sensing mat, in 3 positions, for 30 seconds each: (1) sitting upright; (2) supine; and (3) supine against 30-degree wedge. Measurements were made with and without a padded adhesive bandage overlying the sacrum. Age, sex, and body mass index (BMI) were collected. These variables were entered sequentially, in an a priori order to construct a linear mixed-effects model.

RESULTS

Forty healthy adults participated. After controlling for by-subject variation, age, and sex, BMI did not influence peak sacral pressure (P = 0.22), although the effect of body position was significant (P < 0.01). Subsequent addition of padded adhesive dressing was nonsignificant (P = 0.17); sacral peak pressure was similar with a padded adhesive dressing (247.8 ± 147.3 mm Hg) or without (mean ± standard deviation = 229.8 ± 127.7 mm Hg). Lastly, there was no significant interaction between BMI and body position (P = 0.11).

CONCLUSIONS

Padded adhesive bandages did not reduce interface pressure in any position. Sacral pressure was highest in the supine position and was not specifically affected by BMI. If padded bandages provide clinically significant reduction in pressure injury incidence, it is not simply through the reduction of interface pressure.

Effect of Vibration on Alleviating Foot Pressure-Induced Ischemia under Occlusive Compression

Objectives

Foot ulcers often occur in people with diabetes because of pressure-induced tissue ischemia. Vibration has been reported to be helpful in alleviating mechanical damage and promoting wound healing. The objective of this study is to explore whether vibration can relieve reactive hyperemia in foot tissue under occlusive compression.

Methods

Thirteen healthy adults participated in the study. Each foot was placed under occlusive compression without or with vibration intervention, which was randomly assigned every other day. The dorsal foot skin blood flow (SBF) was measured pre- and postintervention for each subject in each test. Temporal variations and spectral features of SBF were recorded for comparison.

Results

The results showed that subjects displayed an obvious reactive hyperemia in the foot tissue after pressure occlusion, whereas they displayed a more regular SBF when vibration was applied along with occlusive compression. Moreover, the amplitude of metabolic, neurogenic, and myogenic pathways for SBF was significantly reduced during the hyperemia process when vibration was applied.

Conclusions

This study demonstrated that vibration can effectively reduce the level of hyperemia in foot tissue under occlusive compression and also induce less protective physiological regulatory activities. This is helpful for protecting foot tissue from pressure-induced ischemic injury and foot ulcers.

Shifting loads as a result of chair articulations and associated perfusion responses in the context of pressure injuries: An investigation with able-bodied individuals

Wheelchair users with spinal cord injuries experience pressure injuries at high rates, causing a decrease in quality of life and an increased financial burden. The soft tissue in the buttocks (beneath the ischial tuberosities) and lower back (behind the sacrum) experience large interface pressures over long periods while seated, putting them at high risk of pressure injury development. The goals of this research were to evaluate the ability of an articulating chair design to redistribute pressures on the body and to affect blood perfusion in the buttocks tissue over the ischial tuberosities. Using a unique, custom-designed chair developed for this research, pressure and blood perfusion were obtained for numerous seated positions that included recline, seat pan tilt, and back articulations. Reclining the chair back increased maximum pressures in the buttocks and lower back regions, while it decreased maximum pressures in the upper back and thigh regions. Increasing seat pan tilt, or rotating the anterior edge of the seat pan above the posterior edge, decreased maximum pressures in the buttocks and lower back regions and increased perfusion in the buttocks. Results suggested that using back recline and seat pan tilt together to create a whole-body tilt increased pressures in the back and decreased pressures in the buttocks. Changes in back articulation redistributed pressure in all back regions. Thus, the articulating chair design redistributed pressures in all areas of the body and promoted blood perfusion in the buttocks while seated. Pressure redistribution and perfusion promotion are fundamental to reducing pressure injury risk.

Changes in Tissue Composition and Load Response After Transtibial Amputation Indicate Biomechanical Adaptation

Despite the potential for biomechanical conditioning with prosthetic use, the soft tissues of residual limbs following lower-limb amputation are vulnerable to damage. Imaging studies revealing morphological changes in these soft tissues have not distinguished between superficial and intramuscular adipose distribution, despite the recognition that intramuscular fat levels indicate reduced tolerance to mechanical loading. Furthermore, it is unclear how these changes may alter tissue tone and stiffness, which are key features in prosthetic socket design. This study was designed to compare the morphology and biomechanical response of limb tissues to mechanical loading in individuals with and without transtibial amputation, using magnetic resonance imaging in combination with tissue structural stiffness. The results revealed higher adipose infiltrating muscle in residual limbs than in intact limbs (residual: median 2.5% (range 0.2–8.9%); contralateral: 1.7% (0.1–5.1%); control: 0.9% (0.4–1.3%)), indicating muscle atrophy and adaptation post-amputation. The intramuscular adipose content correlated negatively with daily socket use, although there was no association with time post-amputation. Residual limbs were significantly stiffer than intact limbs at the patellar tendon site, which plays a key role in load transfer across the limb-prosthesis interface. The tissue changes following amputation have relevance in the clinical understanding of prosthetic socket design variables and soft tissue damage risk in this vulnerable group.

A Proposal of Implementation of Sitting Posture Monitoring System for Wheelchair Utilizing Machine Learning Methods

This paper presents a posture recognition system aimed at detecting sitting postures of a wheelchair user. The main goals of the proposed system are to identify and inform irregular and improper posture to prevent sitting-related health issues such as pressure ulcers, with the potential that it could also be used for individuals without mobility issues. In the proposed monitoring system, an array of 16 screen printed pressure sensor units was employed to obtain pressure data, which are sampled and processed in real-time using read-out electronics. The posture recognition was performed for four sitting positions: right-, left-, forward- and backward leaning based on k-nearest neighbors (k-NN), support vector machines (SVM), random forest (RF), decision tree (DT) and LightGBM machine learning algorithms. As a result, a posture classification accuracy of up to 99.03 percent can be achieved. Experimental studies illustrate that the system can provide real-time pressure distribution value in the form of a pressure map on a standard PC and also on a raspberry pi system equipped with a touchscreen monitor. The stored pressure distribution data can later be shared with healthcare professionals so that abnormalities in sitting patterns can be identified by employing a post-processing unit. The proposed system could be used for risk assessments related to pressure ulcers. It may be served as a benchmark by recording and identifying individuals’ sitting patterns and the possibility of being realized as a lightweight portable health monitoring device.

Clinical profile of the SEM Scanner - Modernizing pressure injury care pathways using Sub-Epidermal Moisture (SEM) scanning

INTRODUCTION

Pressure injuries (PIs) are a global health concern. Current PI care standards, including skin tissue assessments (STA) and health care professional (HCP) clinical judgment, diagnose visibly manifested PIs on the skin's surface, i.e. after the damage has already occurred. However, objective assessment of early-stage, non-visible, pressure-induced tissue damage is clinically impossible within the current standard of care. The SEM Scanner is the first device authorized by the Food and Drug Administration (FDA) that addresses this unmet clinical need.

AREAS COVERED

This review describes the novel sub-epidermal moisture (SEM) scanning technology of the device and summarizes the clinical safety and efficacy data that support the use of the scanner in routine PI care practice.

EXPERT OPINION

The clinical strategy for developing the SEM Scanner is noteworthy. SEM technology using anatomy-specific data enables HCPs to provide early PI prevention interventions before visible signs of tissue damage develop while the damage is still reversible. When adopted into routine practice, the device identifies an increased risk of developing PIs 5 days (median) earlier than STA. FDA clearance was based on bench studies and data from three foundational trials that demonstrate the diagnostic accuracy of the device algorithm significantly exceeding clinical judgment (p < 0.001).

Key Components Related to Pressure Injury Formation: An Initial Investigation Into Pressure Distribution and Blood Perfusion Responses in Wheelchair Users

Soft tissue around bony prominences in the buttocks and back are high-risk areas prone to the development of pressure injuries. From a clinical perspective, prevention of pressure injuries all together is the ideal situation. Unfortunately, prevalence rates still reach 47% with recurrence rates even higher. The goals of this study were to evaluate the effects of a series of wheelchair movements, some that currently exist in commercial wheelchairs and some new, on interface pressures and perfusion under the buttocks. Twenty-seven chair positions were obtained by varying back recline, seat pan tilt, and articulation of two supports along the back. Although back recline is commonly taught by therapists to be used as a pressure relieving posture, results indicated an increase in pressures under the ischial tuberosities and sacral areas in reclined positions. Articulation of the back supports produced changes in posture moving from an "erect" to "slouched" position. These movements successfully shifted pressures across back regions. Seat pan tilt was effective in shifting pressures off the ischial tuberosity regions. Additionally, in a portion of the participants, seat pan tilt consistently increased perfusion under the ischial tuberosity region. The findings of this research suggest that movements other than back recline should be considered to more effectively alter interface pressures, particularly in high-risk regions like the sacrum and ischial tuberosities.

Monitor for lactate in perspiration

Sweat is a noninvasive biological fluid on the surface of human skin and has attracted increasing attention as a diagnostic specimen for disease and biomarker detection. Sweat metabolite quantification is possible due to progress in sweat analysis techniques; nevertheless, the role of sweat monitoring in energy metabolism, physiological or pathological state assessment, health status assessment, and the development and outcome of metabolism-related diseases remains unclear. This review provides a comprehensive overview of the literature on human sweat lactate concentration. The first, second, and third sections of this review present an introduction of sweat lactate, methods for the collection and storage of sweat lactate samples, and methods of detection and analysis of sweat lactate, respectively. The fourth section elaborates upon the current state of clinical application of sweat lactate monitoring and its prospects for health surveillance. The last section focuses on the challenges and future directions of this novel technology for detecting lactate in sweat.

Our contemporary understanding of the aetiology of pressure ulcers/pressure injuries

In 2019, the third and updated edition of the Clinical Practice Guideline (CPG) on Prevention and Treatment of Pressure Ulcers/Injuries has been published. In addition to this most up‐to‐date evidence‐based guidance for clinicians, related topics such as pressure ulcers (PUs)/pressure injuries (PIs) aetiology, classification, and future research needs were considered by the teams of experts. To elaborate on these topics, this is the third paper of a series of the CPG articles, which summarises the latest understanding of the aetiology of PUs/PIs with a special focus on the effects of soft tissue deformation. Sustained deformations of soft tissues cause initial cell death and tissue damage that ultimately may result in the formation of PUs/PIs. High tissue deformations result in cell damage on a microscopic level within just a few minutes, although it may take hours of sustained loading for the damage to become clinically visible. Superficial skin damage seems to be primarily caused by excessive shear strain/stress exposures, deeper PUs/PIs predominantly result from high pressures in combination with shear at the surface over bony prominences, or under stiff medical devices. Therefore, primary PU/PI prevention should aim for minimising deformations by either reducing the peak strain/stress values in tissues or decreasing the exposure time.

A numerical analysis of skin-PPE interaction to prevent facial tissue injury

The use of close-fitting PPE is essential to prevent exposure to dispersed airborne matter, including the COVID-19 virus. The current pandemic has increased pressure on healthcare systems around the world, leading to medical professionals using high-grade PPE for prolonged durations, resulting in device-induced skin injuries. This study focuses on computationally improving the interaction between skin and PPE to reduce the likelihood of discomfort and tissue damage. A finite element model is developed to simulate the movement of PPE against the face during day-to-day tasks. Due to limited available data on skin characteristics and how these vary interpersonally between sexes, races and ages, the main objective of this study was to establish the effects and trends that mask modifications have on the resulting subsurface strain energy density distribution in the skin. These modifications include the material, geometric and interfacial properties. Overall, the results show that skin injury can be reduced by using softer mask materials, whilst friction against the skin should be minimised, e.g. through use of micro-textures, humidity control and topical creams. Furthermore, the contact area between the mask and skin should be maximised, whilst the use of soft materials with incompressible behaviour (e.g. many elastomers) should be avoided.

Exploring the Role of Pain as an Early Indicator for Individuals at Risk of Pressure Ulcer Development: A Systematic Review

BACKGROUND

Pressure ulcer (PU) development begins with an inflammatory response, arising due to pressure and shear forces causing changes to the cytoskeletal structure of cells. Thus, pain, synonymous with inflammation, may be an indicator of PU development.

AIM

To explore the role of pain as an indicator of PU development and to determine how this pain was measured.

METHOD

We searched PUBMED, CINAHL, SCOPUS, Cochrane, and EMBASE databases. A total of 879 records were returned, with eight satisfying the inclusion criteria. Narrative data synthesis was undertaken. The quality of studies was assessed using the evidence-based librarianship (EBL) checklist.

RESULTS

The studies were conducted between 2000 and 2019, and 75% (n = 6) employed a cross-sectional design. The mean sample size was 760 participants (SD = 703). Of the included studies, 87.5% (n = 7) identified that pain was associated with PU development. The most frequent pain assessment tool was the numeric rating scale (37.5%; n = 3). Using the EBL checklist, 62.5% (n = 5) of the studies scored ≥75%, reflecting validity.

LINKING EVIDENCE TO ACTION

Pain is associated with PU development; however, further research is required to validate these findings and assess the characteristics associated with pain as a symptom preceding PU development.

Positron emission tomography study of effects of two pressure-relieving support surfaces on pressure ulcer development

OBJECTIVE

To study the pathophysiological cascade of pressure ulcer (PU) development consisting of tissue deformation, inflammation and hypoxia.

METHOD

In this crossover study, deformation was measured with computerised tomography (CT) linked with contact area reflecting immersion and envelopment. Inflammation and hypoxia were measured using subepidermal moisture (SEM), skin temperature and tissue perfusion with positron emission tomography. These variables were investigated under 90 minutes of pressure exposure caused by two functionally different support surfaces-a regular foam mattress and a minimum pressure air (MPA) mattress.

RESULTS

A total of eight healthy volunteers took part in the study. There was major tissue deformation when the participants lay on a foam mattress while the tissues retained their original shape on the MPA mattress (p<0.0001). During the pressure exposure, the skin temperature increased significantly on both support surfaces but the final temperature on the foam mattress was about 1oC higher than on the MPA mattress (p<0.0001). SEM increased on both support surfaces compared with an unexposed reference site, but the cause may be different between the two support surfaces. Tissue perfusion was lowest in the skin followed by subcutaneous tissues and highest in the muscles. The pressure exposure did not cause any substantial changes in perfusion. The results showed that tissue deformation was more pronounced, the support surface contact area (envelopment), was smaller and the skin temperature higher on the foam mattress than on the MPA mattress, without significant differences in tissue perfusion.

CONCLUSION

In this study, the MPA mattress support surface had mechanobiological properties that counteracted tissue deformation and thereby may prevent PUs.

Evaluating the sensitivity, specificity and clinical utility of algorithms of spatial variation in sub-epidermal moisture (SEM) for the diagnosis of deep and early-stage pressure-induced tissue damage

BACKGROUND

Sub-epidermal moisture (SEM) is a measurable biomarker detecting early pressure damage in order to objectively support current 'gold standard' skin tissue assessments (STA) for the detection of deep and early-stage pressure-induced injuries or ulcers (PI/PUs).

OBJECTIVE

A multi-site, dual arm, cross sectional, retrospective study was conducted to evaluate the sensitivity, specificity and clinical utility of spatial variation in SEM readings between healthy and damaged skin tissue.

METHOD

The study enrolled 175 subjects: 125 with confirmed PI/PUs or suspected deep tissue injury (sDTI), and 50 confirmed healthy subjects. Expert principal investigators and PI/PU healthcare practitioners (HCPs) evaluating all subjects were trained in SEM measurements but blinded to clinical interpretation of SEM readings. Sequential and spatial SEM readings of the sacrum and heels, subjects' demographic data, STAs, risk assessment tool scores (RATS), pain assessment and potential confounders were recorded. Independent statistical analyses were performed.

RESULTS

Mean spatial SEM measures within subjects with healthy tissue and within subjects with damaged tissue were statistically similar. Mean spatial SEM measures within anatomies of subjects with damaged tissue were significantly different (p<0.05). There was no significant difference between spatial readings in healthy subjects. Algorithms computing a range of SEM delta thresholds indicated a sensitivity of 82-87% and a specificity of 51-88% at an SEM delta ≥0.6. Receiver operating characteristic (ROC) curves computed areas under the curve (AUC) of 0.7809-0.9181 (95% CI: 0.7221-0.8817, 0.8397-0.9545, p<0.0001) exceeding clinical judgement.

CONCLUSION

These SEM data augment clinical decision-making for developing intact skin PI/PUs including sDTIs and Stage I PI/PUs. Informing HCPs of this subclinical, non-visible skin and tissue damage and providing opportunities for alternative PI/PU care pathways is an exciting prospect.

Dressings for preventing pressure ulcers: how do they work?

Pressure ulcers (PUs) negatively affect quality of life (QoL) and cause problems for patients, such as pain, distress and often specific difficulties with treatments used to manage the wound. Thus, it is important to implement appropriate prevention strategies in order to achieve high-quality care, thereby reducing the burden of PUs on patients, the healthcare system and society as a whole. PU development arises due to the adverse effects of pressure, shear, friction and moisture at the skin/surface interface. Preventive interventions typically include risk assessment, reducing pressure and minimising shear and friction. More recently, certain wound dressings, as a potential additional protective strategy for preventing PUs, have been introduced. This review explores the mechanisms of action of dressings for preventing PUs. Findings from the review indicate that decreasing frictional forces transmitted to the patient's skin is achieved by use of a dressing with an outer surface made from a low friction material. Furthermore, the ability of dressings to absorb and redistribute shear forces through good adhesion to the skin, high loft and lateral movement of the dressing layers is important in reducing shear forces. This is achieved when the dressing reduces pressure transmitted to the patient's tissues by the propriety of high loft/thickness and padding that allows a degree of cushioning of bony prominences. Further, dressings may reduce humidity at the skin/dressing interface, i.e., the dressing is absorbent and/or permits moisture to evaporate quickly. As part of an established PU prevention protocol, dressings may help decrease PU incidence.

Risk Factors for Pressure Injury Development Among Critical Care Patients

Identification of the appropriate pressure injury (PI) risk factors is the first step in successful PI prevention. Measuring PI risk through formalized PI risk assessment is an essential component of any PI prevention program. Major PI risk factors identified in the empirical literature in the critical care population include age, diabetes, hypotension, mobility, prolonged intensive care unit admission, mechanical ventilation and vasopressor administration. Future risk assessment using sophisticated data analytics available in the electronic medical record may result in earlier, targeted PI prevention and will improve our understanding of risk factors that may contribute to unavoidable PIs.

A review of foot finite element modelling for pressure ulcer prevention in bedrest: Current perspectives and future recommendations

Pressure ulcers (PUs) are a major public health challenge, having a significant impact on healthcare service and patient quality of life. Computational biomechanical modelling has enhanced PU research by facilitating the investigation of pressure responses in subcutaneous tissue and skeletal muscle. Extensive work has been undertaken on PUs on patients in the seated posture, but research into heel ulcers has been relatively neglected. The aim of this review was to address the key challenges that exist in developing an effective FE foot model for PU prevention and the confusion surrounding the wide range of outputs reported. Nine FE foot studies investigating heel ulcers in bedrest were identified and reviewed. Six studies modelled the posterior part of the heel, two included the calf and foot, and one modelled the whole body. Due to the complexity of the foot anatomy, all studies involved simplification or assumptions regarding parts of the foot structure, boundary conditions and material parameters. Simulations aimed to understand better the stresses and strains exhibited in the heel soft tissues of the healthy foot. The biomechanical properties of soft tissue derived from experimental measurements are critical for developing a realistic model and consequently guiding clinical decisions. Yet, little to no validation was reported in each of the studies. If FE models are to address future research questions and clinical applications, then sound verification and validation of these models is required to ensure accurate conclusions and prediction of patient outcomes. Recommendations and considerations for future FE studies are therefore proposed.

A combined experimental and computational approach to evaluate microclimate control at the support surface interface

Temperature and humidity conditions at the interface between a support surface and the skin, termed microclimate, has been implicated in the development of pressure ulcers. Support surface technologies have been developed to control microclimate conditions, although only a few standard test methods exist to evaluate their performance. This study describes a combined experimental-computational approach to analyzing microclimate control systems. The study used a modified physical model protocol to evaluate two specific support surface systems involving a spacer fabric cover with i) no air flow and ii) an active fan. The physical model deposited moisture at a controlled rate for 25 min, and the microclimate conditions under the model and the surrounding area were monitored for 24 h. Using the experimental data as boundary conditions, a finite element model was developed using mass transport principles, which was calibrated using experimental results. Model inputs included mass density and mass diffusivity, resulting in an estimated absolute humidity change over time. The physical model tests revealed distinct differences between the support surfaces with and without active airflow, with the former having little effect on local humidity levels (RH>75% for 24hr). By contrast, there was a spatial and temporal change in microclimate with the active fan, with sensors positioned towards the source of airflow reaching ambient conditions within 24hr. The computational model was refined to produce comparable results with respect to both the spatial distribution of microclimate and the change in values over time. The combined experimental and computation approach was able to distinguish distinct difference in microclimate change between two support surface designs. The approach could enable the efficient evaluation of different mattress design principles to aid decision making for personalized support surface solutions, for the prevention of pressure ulcers.

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.

Key considerations for finite element modelling of the residuum-prosthetic socket interface

BACKGROUND

Finite element modelling has long been proposed to support prosthetic socket design. However, there is minimal detail in the literature to inform practice in developing and interpreting these complex, highly nonlinear models.

OBJECTIVES

To identify best practice recommendations for finite element modelling of lower limb prosthetics, considering key modelling approaches and inputs.

STUDY DESIGN

Computational modelling.

METHODS

This study developed a parametric finite element model using magnetic resonance imaging data from a person with transtibial amputation. Comparative analyses were performed considering socket loading methods, socket-residuum interface parameters and soft tissue material models from the literature, to quantify their effect on the residuum's biomechanical response to a range of parameterised socket designs.

RESULTS

These variables had a marked impact on the finite element model's predictions for limb-socket interface pressure and soft tissue shear distribution.

CONCLUSIONS

All modelling decisions should be justified biomechanically and clinically. In order to represent the prosthetic loading scenario in silico, researchers should (1) consider the effects of donning and interface friction to capture the generated soft tissue shear stresses, (2) use representative stiffness hyperelastic material models for soft tissues when using strain to predict injury and (3) interrogate models comparatively, against a clinically-used control.

Tissue matters: In-vivo tissue properties of persons with spinal cord injuries to inform clinical models for pressure ulcer prevention

The prevalence of pressure ulcers in patients with spinal cord injuries has been estimated to be between 30% and 47%. Individuals with spinal cord injuries sit for a majority of the time, increasing the risk of developing pressure ulcers in the buttocks and thighs due to large internal stresses. Human body models have been developed to study the formation of pressure ulcers, yet a persistent limitation in these models has been the material properties used to represent the soft tissues in the buttocks and thighs. Specifically, soft tissue material property data have not included wheelchair users, such as those with spinal cord injuries. The goals of this research were 1) to determine the in-vivo material properties of soft tissue in the thighs and buttocks of individuals with spinal cord injuries and 2) compare these to properties obtained from able-bodied people. Results indicated that the proximal and middle thigh regions of those who had a spinal cord injury were softer than the same regions as able-bodied individuals, while the distal thigh regions were stiffer. These findings are vital because they indicate that models developed using properties from able-bodied individuals will not produce internal stress or strain magnitudes that represent individuals who have a spinal cord injury. This information suggests that models should obtain material property data sets from their desired population. Human body models must represent the population being studied if they are to inform clinical assessments and make accurate patient predictions.

Deep tissue injury: a narrative review on the aetiology of a controversial wound

Deep tissue injuries (DTIs) were added to pressure ulcer grading systems in 2009. Since then, they have been associated with the same aetiological processes as other forms of pressure injury (PI). This is despite notable clinical differences in their presentation along with variations in natural history that suggest they are the consequence of processes distinct from those that cause other PIs. Understanding the aetiology of DTIs is essential to guide prevention and treatment in addition to ensuring healthcare governance processes deeply tied to pressure injury are effective and efficient. Current understanding of the aetiology of DTI has significant gaps, with several key challenges impeding progress in this area of PI research, including inconsistent reporting by healthcare services and the limitations of animal and computer models in addition to the ethical barriers to conducting studies on human subjects. Synthesis of early studies with studies undertaken before 2009 is also limited by the variety in definitions of DTI used before that published by the European Pressure Ulcer Advisory Panel, the National Pressure Injury Advisory Panel and the Pan Pacific Pressure Injury Alliance in 2009. To date, few prospective clinical studies have been conducted. This article presents a narrative review on the clinical and animal study evidence indicating contemporary understanding of DTI.