The effect of pressure and shear on tissue viability of human skin in relation to the development of pressure ulcers: a systematic review

On the Move pad - a portable multipurpose pad: User feedback

CONTEXT/OBJECTIVE

Hard-shell toilet seats may compromise safety and hinder the participation of individuals at risk for pressure injuries (PIs) when using these facilities away from home in public, hotel, or family/friend restrooms. Moreover, people often add "wash-cloths" for additional padding for comfort, and to reduce the risk of PIs due to pressure or shearing on their wheelchairs surfaces. This study investigated the utilization of portable pads, initially designed for toilet use but adaptable to various places and contexts, while examining pad usability.

DESIGN

A cross-sectional descriptive survey design.

SETTING

Inpatient care, outpatient care, and community setting.

PARTICIPANTS

45 individuals at risk of PIs.

RESULTS

Participants extended the use of these pads beyond toilets, employing them as wheelchair armrest and leg rest pads in other settings. Feedback from a customized questionnaire indicated high levels of usefulness (8.5/10) and ease of use (9.1/10) attributed to the pads. Among the features, the top three favored were ease of use, comfort/cushioning, and function. Participants expressed a desire for a variety of sizes and colors to enable versatile usage and suggested incorporating a pocket for storing small items.

CONCLUSIONS AND RELEVANCE

Individuals at risk of PIs require cushioning not only on hard-shell toilet seats, but also for additional padding, protection and enhancing the use of wheelchairs. Rehabilitation professionals can play a crucial role in educating and training both clients and caregivers to understand PI prevention, enabling them to effectively leverage the pads in appropriate situations, thereby enhancing their comfort in their wheelchairs during social engagement.

An evaluation of the effects of localised skin cooling on microvascular, inflammatory, structural, and perceptual responses to sustained mechanical loading of the sacrum: A study protocol

This study protocol aims to investigate how localised cooling influences the skin's microvascular, inflammatory, structural, and perceptual tolerance to sustained mechanical loading at the sacrum, evaluating factors such as morphology, physiology, and perceptual responses. The protocol will be tested on individuals of different age, sex, skin tone and clinical status, using a repeated-measure design with three participants cohorts: i) young healthy (n = 35); ii) older healthy (n = 35); iii) spinal cord injured (SCI, n = 35). Participants will complete three testing sessions during which their sacrum will be mechanically loaded (60 mmHg; 45 min) and unloaded (20 min) with a custom-built thermal probe, causing pressure-induced ischemia and post-occlusive reactive hyperaemia. Testing sessions will differ by the probe's temperature, which will be set to either 38°C (no cooling), 24°C (mild cooling), or 16°C (strong cooling). We will measure skin blood flow (via Laser Doppler Flowmetry; 40 Hz); pro- and anti-inflammatory biomarkers in skin sebum (Sebutape); structural skin properties (Optical Coherence Tomography); and ratings of thermal sensation, comfort, and acceptance (Likert Scales); throughout the loading and unloading phases. Changes in post-occlusive reactive hyperaemia will be considered as the primary outcome and data will be analysed for the independent and interactive effects of stimuli's temperature and of participant group on within- and between-subject mean differences (and 95% Confidence Intervals) in peak hyperaemia, by means of a 2-way mixed model ANOVA (or Friedman). Regression models will also be developed to assess the relationship between absolute cooling temperatures and peak hyperaemia. Secondary outcomes will be within- and between-subject mean changes in biomarkers' expression, skin structural and perceptual responses. This analysis will help identifying physiological and perceptual thresholds for the protective effects of cooling from mechanically induced damage underlying the development of pressure ulcers in individuals varying in age and clinical status.

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.

Review of assistive devices for the prevention of pressure ulcers: an engineering perspective

PURPOSE

Pressure ulcers (PUs) are prevalent among immobile bed or wheelchair-reliant individuals who experience prolonged sedentary positions. Pressure relief and frequent repositioning of body posture help to mitigate complications associated with PUs. Adherence with regular repositioning is difficult to maintain due to nursing labour shortages or constraints of in-home caregivers. Manual repositioning, transferring, and lifting of immobile patients are physically demanding tasks for caregivers. This review aimed to explore and categorize these devices, discuss the significant technical challenges that need addressing, and identify potential design opportunities.

MATERIALS AND METHODS

In this review, a literature search was conducted using PubMED, Science Direct, Google Scholar and IEEE Xplore databases including studies from 1995 until Feb 2023 with keywords such as pressure ulcer, assistive device, pressure relief, repositioning, transfer, etc. Both commercial and research-level devices were included in the search.

RESULTS

142 devices or technologies were identified and classified into four main categories that were further subcategorized. Within each category, the devices were investigated in terms of their mechanical design, actuation methods, control strategies, sensing technologies, and level of autonomy. Limitations of current technologies are design complexity, lack of patient comfort, and a lack of autonomy requiring caregivers frequent intervention.

CONCLUSIONS

Several devices have been developed to help with prevention and mitigation of PUs. There remain challenges that hinder the widespread accessibility and use of current technologies. Advancements in assistive technologies for pressure ulcer mitigation could lie at the intersection of robotics, sensors, perception, user-centered design, and autonomous systems.

Vulnerability to Decubitus Ulcers and Their Association With Healthcare Utilization: Evidence From Nationwide Inpatient Sample Dataset From 2016 to 2020 in US Hospitals

OBJECTIVE

The aim of the study is to identify vulnerable populations at risk of developing decubitus ulcers and their resultant increase in healthcare utilization to promote the use of early prevention methods.

METHODS

The National Inpatient Sample of the United States was used to identify hospitalized patients across the country who had a length of stay of 5 or more days (N = 9,757,245, weighted N = 48,786,216) from 2016 to 2020. We examined the characteristics of the entire inpatient sample based on the presence of decubitus ulcers, temporal trends, risk of decubitus ulcer development, and its association with healthcare utilization, measured by discounted hospital charges and length of stay. The multivariate survey logistic regression model was used to identify predictors for decubitus ulcer occurrence, and the survey linear regression model was used to measure how decubitus ulcers are associated with healthcare utilization.

RESULTS

Among 48,786,216 nationwide inpatients, 3.9% had decubitus ulcers. The percentage of inpatients with decubitus ulcers who subsequently experienced increased healthcare utilization rose with time. The survey logistic regression results indicate that patients who were Black, older, male, or those reliant on Medicare/Medicaid had a statistically significant increased risk of decubitus ulcers. The survey linear regression results demonstrate that inpatients with decubitus ulcers were associated with increased hospital charges and longer lengths of stay.

CONCLUSIONS

Patients with government insurance, those of minority races and ethnicities, and those treated in the Northeast and West may be more vulnerable to pressure ulcers and subsequent increased healthcare utilization. Implementation of early prevention methods in these populations is necessary to minimize the risk of developing decubitus ulcers, even if upfront costs may be increased. For example, larger hospitals were found to have a lower risk of decubitus ulcer development but an increased cost of preventative care. Hence, it is imperative to explore and use universal, targeted preventative methods to improve patient safety.

Tryptanthrin promotes pressure ulcers healing in mice by inhibiting macrophage-mediated inflammation via cGAS/STING pathways

BACKGROUND

Pressure ulcers (PUs) is ischemic necrosis caused by long-term local tissue pressure, directly affecting postoperative functional recovery. There is evidence that inflammation has an adverse impact on the development of PUs and contributes to unfavorable outcomes, suggesting that blocking the inflammatory response may be a promising therapeutic strategy for PUs. Tryptanthrin (Tryp), a natural product isolated from indigenous plants, has an anti-inflammatory biological function. However, the efficacy of Tryp in PUs remains unclear.

METHODS

Efficacy of Tryp suppressed inflammation was assessed using magnets-induced PUs model in mice. Hematoxylin-Eosin staining, masson staining and immunohistochemistry were used to evaluate the histologic changes after the formation of PUs. The expression of inflammatory cytokines was detected by qRT-PCR. And we detected the expression of protein by Western blotting.

RESULTS

Tryp could promote wound healing, such as epidermal thickening, revascularization, and nerve regeneration. Then the treatment of Tryp was able to promote fibroblast migration and collagen deposition. Moreover, Tryp attenuated inflammation through inducing macrophage polarization to M2 phenotype by suppressing the activation of cGAS-STING pathway.

CONCLUSION

Tryp could reduce the release of inflammatory cytokines, and induce RAW 264.7 polarization to M2 phenotype by targeting cGAS/STING/TBK1 pathways. In summary, Tryp may be a novel medicine for the treatment of PUs in the future.

Investigating change of discomfort during repetitive force exertion though an exoskeleton cuff

This article investigates discomfort development for forces exerted repetitively and for extended durations through a rigid cuff. Three force patterns, chosen to mimic exoskeleton use, were applied to the thigh of 15 healthy participants for 30 min. Changes in perceived comfort and skin effects were recorded. Discomfort was detected at normal forces ranging from 40 to >230 N. Repetitive force application triggered discomfort after a median of 4.1 min (normal force only) and 5.4 min (normal and shear force) respectively. Discomfort increased over time but the repetitive force applications did generally not result in pain and there were no significant differences between repetitive loading patterns. Exoskeleton design and use should be informed by comfort thresholds specific to prolonged repetitive loading. Large interindividual differences in perception of discomfort limit the possibilities for generally applicable comfort thresholds. Further research is needed to investigate how patient groups perceive such repetitive loading.

Pressure in the Operating Room: A Potential Contributor to Hospital-Acquired Pressure Injuries

Burn patients are at risk for hospital-acquired pressure injuries (HAPIs). An unexamined factor that may contribute to HAPI development is the effect of pressure from the operating table during surgery. The purpose of this study was to measure pressure on the buttocks and sacral area during burn surgery under general anesthesia (GA). Prospective study of consecutive adult burn patients admitted to an ABA-verified burn center who required surgery under GA between January 06, 2022 and December 08, 2022. We studied only cases that were supine, including those with both legs down (LD), one leg suspended (1LU), or both legs suspended (2LU). Interface pressures on the buttocks and sacral area were measured using a commercial sensor mat. Thousands of individual pressure measurements were integrated to show average and peak pressures over repetitive 10-minute intervals during the entire operation. Recordings were completed in 41 procedures among 28 patients (48.3 ± 16.9 years, % TBSA burn 19.2 ± 17.1, weight 80.2 ± 19.7 kg, BMI 26.7 ± 6.2). Both average pressure (Pave) and peak pressure (Ppeak) increased significantly with greater number of elevated legs (p < .001). During 2LU periods, Ppeak exceeded 100 mmHg for almost half the operative duration. Pave crept steadily upwards over time and had a positive relationship with weight, regardless of leg elevation. Prolonged moderate to high pressures are exerted on the sacral and buttock areas, especially with one or both legs suspended, during burn surgery. These novel observations suggest that pressure from the operating table could contribute to HAPI development.

Classification of wheelchair pressure relief maneuvers using changes in center of pressure and weight on the seat

BACKGROUND

Pressure injuries from prolonged sitting are a significant problem for wheelchair users incurring high costs in healthcare expenditures and reducing quality-of-life. There is a need to improve pressure relief training and adherence in a variety of settings.

OBJECTIVE

To identify effective common wheelchair pressure relief (PR) manoeuvres based on changes to users' seated centre of pressure (CoP) and seated weight.

PARTICIPANTS

20 individuals who use manual wheelchairs as their primary means of mobility.

METHODS

Participants performed 5 types of PR including seated push-ups, leftward, rightward, forward, and backward leans-while sitting in a wheelchair equipped with a custom instrumented seat pan support. Data were analysed using both clustering and decision tree approaches to identify types of PR.

RESULTS

Both clustering and decision tree approaches were able to identify and classify PR though neither could accurately distinguish between forward and backward PR.

CONCLUSION

Changes in the centre of pressure and the total weight on the wheelchair's seat can be used to automatically characterise type, amplitude and duration of pressure relief manoeuvres. Building such a classification and quality assessment scheme into an algorithm could enable a virtual coaching system to track users' pressure relief behaviour and make suggestions to improve adherence with clinical recommendations.IMPLICATIONS FOR REHABILITATIONMultiple bending beam load cells can be used to measure wheelchair users' seated centre of pressure independent of type of cushion used.Both cluster analysis and decision tree algorithms can classify commonly practiced pressure reliefs by measuring changes to the centre of pressure and total weight on the wheelchair's seat.The combination of force sensing for centre of pressure determination and either algorithm could serve as the basis for an application to coach wheelchair users to do effective pressure reliefs.

Systematic Review for Risks of Pressure Injury and Prediction Models Using Machine Learning Algorithms

Pressure injuries are increasing worldwide, and there has been no significant improvement in preventing them. This study is aimed at reviewing and evaluating the studies related to the prediction model to identify the risks of pressure injuries in adult hospitalized patients using machine learning algorithms. In addition, it provides evidence that the prediction models identified the risks of pressure injuries earlier. The systematic review has been utilized to review the articles that discussed constructing a prediction model of pressure injuries using machine learning in hospitalized adult patients. The search was conducted in the databases Cumulative Index to Nursing and Allied Health Literature (CINAHIL), PubMed, Science Direct, the Institute of Electrical and Electronics Engineers (IEEE), Cochrane, and Google Scholar. The inclusion criteria included studies constructing a prediction model for adult hospitalized patients. Twenty-seven articles were included in the study. The defects in the current method of identifying risks of pressure injury led health scientists and nursing leaders to look for a new methodology that helps identify all risk factors and predict pressure injury earlier, before the skin changes or harms the patients. The paper critically analyzes the current prediction models and guides future directions and motivations.

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.

Participatory action design and engineering of a manual wheelchair virtual coach including in-home and community usage

BACKGROUND

Current clinical practice guidelines (CPG) recommend periodic pressure redistribution (PR) to alter sitting pressure and reduce the risk of developing pressure injuries (PI). Individuals who have strength and trunk stability are asked to perform PR such as wheelies, leaning laterally, and forward-leaning to minimize the duration of pressure acting on the same region of the body.

OBJECTIVE

Our long-term objective is to build upon previous research and development to create a more effective device for improving PR training and adherence to CPG among manual wheelchair users (MWU). Through this study, we employed a participatory action design and engineering (PADE) approach in developing the hardware and user interface to increase the likelihood of eventually yielding a device effective for both MWU and clinicians.

PARTICIPANTS

Focus Groups: Ten clinicians - 6 physical therapists, 3 occupational therapists, and one registered nurse, and 10 MWU with spinal cord injuries (SCI) who reported using their wheelchairs 40-80 h per week. Five-Day Assessment: Five male MWU with SCI who had been wheelchair users for 18.5 ± 16.2 years. Four-Week Investigation: The 7 participants with SCI were 5 males and 2 females, who had been wheelchair users for 24.7 ± 17.0 years.

METHODS

A PADE approach was used to improve upon a manual wheelchair virtual coaching system for people with SCI. The system comprises a seat support instrumented with force sensors, software algorithms to detect PR, and a smart phone app for user interface. The methods included three stages: multiple focus groups, a five-day evaluation phase with participants using their own wheelchairs in their homes and communities, and a 4-week assessment with improvements made based on the 5-day results by users with their own wheelchairs in their homes and communities.

RESULTS

The focus groups yielded guidance for ergonomics, user interface, charging frequency, and key dimensions and mass. The 5-day study identified mechanical, electrical, and connectivity challenges, which were resolved before the 4-week study. The 4-week trial suggested that participants performed PR less frequently than clinically recommended and provided an indication of the types of maneuvers that they performed.

CONCLUSION

A prototype manual wheelchair virtual coaching system was developed using a PADE process. The system was able to detect and record PR in home and community environments. Following improvements identified in this study, a future version will be tested with additional users to determine whether it can improve adherence to PR guidance.

Using electrocardiogram electrodes to monitor skin impedance spectroscopic response when skin is subjected to sustained static pressure

Background

Impedance spectroscopy is a non-invasive technique which can be used to monitor skin barrier function, with potential applications in early-stage pressure ulcer detection. This paper describes how changes in skin impedance, due to mechanical damage of the stratum corneum by tape stripping or applied pressure, can be straightforwardly measured using commercial electrocardiogram electrodes and a relatively low-cost impedance analyser. Two models of pressure injury were studied, an ex vivo porcine and in vivo human skin model.

Objectives

Determine whether impedance spectroscopy may have potential utility in measuring the effect on skin of applied pressure on early-stage pressure injury.

Methods

Two models were utilized to measure the effect of pressure. Porcine model: 0, 7.5, 15 or 22.5 mmHg of pressure was applied for up to 24 h (N = 4) and monitored at various time intervals. Human Model: 88 mmHg of pressure was applied for four sets of three-minute intervals (N = 13) and post-pressure recovery was monitored for 4 h. For each model, skin impedance was monitored at 0.1 Hz-50 kHz using disposable Ag/AgCl electrodes. The data was analysed using Ordinary One-Way Analysis of Variance.

Results

Porcine model: after 24 h, the impedance of pressure-loaded skin was significantly reduced compared to the non-loaded control group (p ≤ 0.0001); this reduction in impedance was proportional to the degree of mechanical loading. Histology images of skin cross-sections provided qualitative evidence that the epidermis was structurally compromised by pressure. Human Model: the response of healthy skin to applied pressure displayed inter-variation. Participants with a significant change in skin impedance (p ≤ 0.01) also demonstrated signs of erythema.

Conclusions

This study suggests that using impedance spectroscopy to measure skin (stratum corneum) resistance may have utility in giving early warning of skin pressure injury prior to clinical symptoms, with a good correlation between observed erythema and reduction in skin resistance. Further work should be initiated on patients at risk of pressure injury to improve intervention strategies, including in darker skin tones where early-stage pressure injuries may not be visually distinct.

Risk factors and the nomogram model for intraoperatively acquired pressure injuries in children with brain tumours: A retrospective study

This study aimed to investigate the clinical features and incidence of Intraoperatively Acquired Pressure Injuries (IAPIs) of brain tumours in children, to screen the risk factors and to establish a nomogram model for making prevention strategies against the development of IAPIs. Clinical data of 628 children undergoing brain tumour surgery from August 2019 to August 2021 were extracted from the adverse events and the electronic medical systems. They were randomly divided into a training cohort(n = 471) and a validation cohort(n = 157). The univariate and multivariate analysis was performed to identify the risk factors in training cohort; R software was used to construct a nomogram model; the area under the receiver operator characteristic curve (AUC) and calibration plots were used to judge the predictive performance of the nomogram model; decision curve analysis (DCA) was used to assess the clinical usefulness of the nomogram model. Age, haemorrhage, use of vasopressor, temperature, operation time and operation position were considered as significant risk factors, and enrolled to construct a nomogram model. The results of AUC showed satisfactory discrimination of the nomogram; the calibration plots indicated favourable consistency between the prediction of the nomogram and actual observations in both the training and validation cohorts; DCA showed better net benefit and threshold probability of the nomogram model. The nomogram model illustrates significant predictive ability, which can provide scientific and individual guidance for preventing development of IAPIs.

Determining frictional properties of pants and cushion cover materials using human soft tissue and a rigid sled and how they affect seated shear forces

Shear forces on the buttocks while seated are directly linked to friction, yet the frictional properties at the seat interface are unknown. Shear forces are one of the factors related to increase risk of pressure injury formation. The goals of this study included determining coefficients of friction between three cushion covers and two clothing fabrics using a mechanical system as well as human participants and to evaluate the impact of the cushion covers on shear loading on the buttocks while seated. A chair with separate seat pan tilt and back recline movements was built and instrumented with reflective markers and a load cell. A motion capture system and load cell were used to determine the angles of seat pan tilt at which the sled and participants started sliding, as well as shear forces at three recline angles for three cushion covers (vinyl, one-layer nylon, and two-layer nylon). Results showed the vinyl and two-layer nylon cushion covers respectively had the largest and smallest coefficients of friction for both pants materials. The coefficients of friction calculated with the human participants and rigid sled were within 10% of each other, demonstrating similar results. Further, increasing back recline increased shear load on the buttocks, while the two-layer nylon cover reduced shear forces seen on the buttocks. This work furthers the understanding of shear loading on the buttocks, will aid in the protocols for reducing pressure injuries, and suggests that coefficients of friction found using rigid bodies may be applied to deformable bodies.

A Wearable Textile-Embedded Dielectric Elastomer Actuator Haptic Display

With advances in mobile computing and virtual/augmented reality technologies, communicating through touch using wearable haptic devices is poised to enrich and augment current information delivery channels that typically rely on sight and hearing. To realize a wearable haptic device capable of effective data communication, both ergonomics and haptic performance (i.e., array size, bandwidth, and perception accuracy) are essential considerations. However, these goals often involve challenging and conflicting requirements. We present an integrated approach to address these conflicts, which includes incorporating multilayered dielectric elastomer actuators, a lumped-parameter model of the skin, and a wearable frame in the design loop. An antagonistic arrangement-consisting of an actuator deforming the skin-was used to achieve effective force transmission while maintaining a low profile, and the effect of the wearable frame and structure was investigated through lumped-model analysis and human perception studies.

Does Sacrococcygeal Skeletal Morphology and Morphometry Influence Pressure Injury Formation in Adults?

GENERAL PURPOSE

To present a study that investigated sacrococcygeal skeletal structure as a possible nonmodifiable intrinsic risk factor for pressure injury and identify possible issues caused by its morphology.

TARGET AUDIENCE

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

LEARNING OBJECTIVES/OUTCOMES

After participating in this educational activity, the participant will:1. Recognize the background information the authors considered when planning and conducting their study of sacrococcygeal skeletal structure as a possible pressure injury risk factor.2. Identify the characteristics of the two groups of study participants.3. Choose the results of the study clinicians may consider when implementing evidence-based practice.

Application of an infrared thermography-based model to detect pressure injuries: a prospective cohort study

BACKGROUND

It is challenging to detect pressure injuries at an early stage of their development.

OBJECTIVES

To assess the ability of an infrared thermography (IRT)-based model, constructed using a convolution neural network, to reliably detect pressure injuries.

METHODS

A prospective cohort study compared validity in patients with pressure injury (n = 58) and without pressure injury (n = 205) using different methods. Each patient was followed up for 10 days.

RESULTS

The optimal cut-off values of the IRT-based model were 0·53 for identifying tissue damage 1 day before visual detection of pressure injury and 0·88 for pressure injury detection on the day visual detection is possible. Kaplan-Meier curves and Cox proportional hazard regression model analysis showed that the risk of pressure injury increased 13-fold 1 day before visual detection with a cut-off value higher than 0·53 [hazard ratio (HR) 13·04, 95% confidence interval (CI) 6·32-26·91; P < 0·001]. The ability of the IRT-based model to detect pressure injuries [area under the receiver operating characteristic curve (AUC)_{lag 0 days} , 0·98, 95% CI 0·95-1·00] was better than that of other methods.

CONCLUSIONS

The IRT-based model is a useful and reliable method for clinical dermatologists and nurses to detect pressure injuries. It can objectively and accurately detect pressure injuries 1 day before visual detection and is therefore able to guide prevention earlier than would otherwise be possible. What is already known about this topic? Detection of pressure injuries at an early stage is challenging. Infrared thermography can be used for the physiological and anatomical evaluation of subcutaneous tissue abnormalities. A convolutional neural network is increasingly used in medical imaging analysis. What does this study add? The optimal cut-off values of the IRT-based model were 0·53 for identifying tissue damage 1 day before visual detection of pressure injury and 0·88 for pressure injury detection on the day visual detection is possible. Infrared thermography-based models can be used by clinical dermatologists and nurses to detect pressure injuries at an early stage objectively and accurately.

A Novel Low-Cost 3D Printed Brace Design Method for Early Onset Scoliosis

Early onset scoliosis (EOS) is a type of spine deformity that presents before 10 years of age. The biomechanical properties in scoliosis have been found to be di?erent, especially in the case of the concave and convex paraverte-bral muscles. Based on this fact, a novel 3d printed patient-specific asymmetric stiffness brace design method is proposed in this paper, aiming to provide asymmetric stiffness to match "imbalanced" biomechanical properties of the concave and convex paravertebral muscles, respectively, and treat EOS by applying the block-structure brace.A 3d CAD draft model of the brace contour was implemented from 3D scanning. The asymmetric stiffness block-structure brace was designed in Rhinoceros and the Finite Ele-ment (FE) model was imported into ABAQUS. FE simulation was employed to study the mechanical characteristics of the brace, which provided a quan-titative index for the "imbalanced" property of brace stiffness. The results of the FE simulation showed that the stiffnesses of the concave and convex sides were 145.88 N/mm and 35.95 N/mm, respectively. The block-structure brace was fabricated using 3d printing. Asymmetric stiffness was evaluated by corrective force measurements, which were obtained from a thin-film pressure sensor equipped on the brace. The patient-specific asymmetric stiffness brace was applied to clinical practice in a one-year old EOS patient. A novel low-cost 3D printed brace design method for EOS was proposed in this study that could potentially be useful in patient treatment acceptance.

Photobiomodulation associated with lipid nanoparticles and hyaluronic acid accelerate the healing of excisional wounds

Objectives: This article aimed to investigate the effects of the association between photobiomodulation and hyaluronic acid incorporated in lipid nanoparticles in an epithelial lesion model in inflammatory parameters and oxidative stress. Methods: Eighty Wistar rats were randomly assigned to the following groups: epithelial lesion group (EL); EL+PBM; EL+HA; EL+SLNs; EL+SLNs-HA; EL+PBM+HA; EL+PBM+SLNs; EL+PBM+SLNs-HA. The animals were anesthetized with 4% isofluorane after shaving and induced to an epithelial lesion. Topical treatment with a gel containing HA (0.9%) and/or SLNs (10 mg/mL) and with laser irradiation occurred daily for 1 week. Results: The results showed an increase in wound contraction on the seventh day in the LE + LBM + AH-NPL group, a reduction in pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α), an increase in anti-inflammatory cytokines (IL- 4 and IL-10) and TGF-β. The levels of pro-inflammatory cytokine IL-4 and TGF-β also showed an increase in the LE + NPL-AH, LE + FBM + AH, LE + FBM + NPL and LE + FBM + NPL-AH groups. Regarding oxidative stress parameters, the levels of DCF and nitrite decreased in the combined therapy group when compared to the control group, as well as oxidative damage (carbonyl and sulfhydryl). In the antioxidant defense, there was an increase in GSH and SOD in the combination therapy group. Histological analysis showed a reduction in inflammatory infiltrate in the combination therapy group. The number of fibroblasts and the compaction of collagen fibers did not obtain significant responses. Conclusions: Results analyzed together showed that the combined therapy favored the repair process, and that studies can be carried out to enhance the histological analysis therapy favored the tissue repair process and that studies can be carried out to enhance the histological analysis.

A Cartoon Version of Braden Scale to Assess the Risk of Pressure Injury: Content Validity and Interrater Reliability Study

INTRODUCTION

The Braden Scale is widely used to assess the risk of pressure injury. However, the vague literal description of the items creates difficulties for bedside nurses and limits its sensitivity. To solve this problem, we developed a cartoon version of the Braden scale (CVBS) to improve the pressure injury risk assessment ability of bedside nurses.

METHODS

The CVBS was constructed by two nurses, and the final version was determined through a two-round Delphi consultation. The scale's content validity was calculated based on expert ratings. A total of 265 patients were evaluated simultaneously with the CVBS by 119 bedside nurses and 46 wound care specialists; and 114 bedside nurses and the same 46 wound care specialists evaluated 239 patients with the original Braden scale (OBS). The interrater reliability between the two groups was calculated as Kappa value, and then the Kappa values of the two versions were compared.

RESULTS

The content validity for the draft scale was not good enough. After modification, the indices of all the items in the final CVBS reached 1.00. The Kappa value of the OBS was 0.69 (95% CI 0.61-0.76); for each item, it ranged from 0.60 to 0.80. The interrater reliabilities of the CVBS were higher than those of the OBS, with an overall kappa value of 0.87 (95% CI 0.81-0.92) and a range of 0.77 to 0.93 for each item. The differences between the Kappa values of the CVBS and those of the OBS were all statistically significant.

CONCLUSIONS

The CVBS had good validity and showed higher interrater reliability than the OBS, indicating that it may improve bedside nurses' ability to assess pressure injury risk.

Mechanical modeling and characterization of human skin: A review

This paper reviews the advances made in recent years on modeling approaches and experimental techniques to characterize the mechanical properties of human skin. The skin is the largest organ of the human body that has a complex multi-layered structure with different mechanical behaviors. The mechanical properties of human skin play an important role in distinguishing between healthy and unhealthy skin. Furthermore, knowing these mechanical properties enables computer simulation, skin research, clinical studies, as well as diagnosis and treatment monitoring of skin diseases. This paper reviews the recent efforts on modeling skin using linear, nonlinear, viscoelastic, and anisotropic materials. The work also focuses on aging effects, microstructure analysis, and non-invasive methods for skin testing. A detailed explanation of the skin structure and numerical models, such as finite element models, are discussed in this work. This work also compares different experimental methods that measure the mechanical properties of human skin. The work reviews the experimental results in the literature and shows how the mechanical properties of human skin vary with the skin sites, the layers, and the structure of human skin. The paper also discusses how state-of-the-art technology can advance skin research.

Changes in the three-dimensional microscale topography of human skin with aging impact its mechanical and tribological behavior

Human skin enables interaction with diverse materials every day and at all times. The ability to grasp objects, feel textures, and perceive the environment depends on the mechanical behavior, complex structure, and microscale topography of human skin. At the same time, abrasive interactions, such as sometimes occur with prostheses or textiles, can damage the skin and impair its function. Previous theoretical and computational efforts have shown that skin’s surface topography or microrelief is crucial for its tribological behavior. However, current understanding is limited to adult surface profiles and simplified two-dimensional simulations. Yet, the skin has a rich set of features in three dimensions, and the geometry of skin is known to change with aging. Here we create a numerical model of a dynamic indentation test to elucidate the effect of changes in microscale topography with aging on the skin’s response under indentation and sliding contact with a spherical indenter. We create three different microrelief geometries representative of different ages based on experimental reports from the literature. We perform the indentation and sliding steps, and calculate the normal and tangential forces on the indenter as it moves in three distinct directions based on the characteristic skin lines. The model also evaluates the effect of varying the material parameters. Our results show that the microscale topography of the skin in three dimensions, together with the mechanical behavior of the skin layers, lead to distinctive trends on the stress and strain distribution. The major finding is the increasing role of anisotropy which emerges from the geometric changes seen with aging.

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.

Can plantar fibroblast implantation protect amputees from skin injury? A recipe for skin augmentation

Skin injuries remain a persistent problem for users of lower-limb prostheses despite sustained progress in prosthesis design. One factor limiting the prevention of skin injuries is that skin on the residual limb is not suited to bear the mechanical loads of ambulation. One part of the body that is suited to this task is the sole of the foot. Here, we propose a novel strategy to actively augment skin's tolerance to load, increasing its resistance to mechanically induced injuries. We hypothesise that the load tolerance of skin can be augmented by autologous transplantation of plantar fibroblasts into the residual limb dermis. We expect that introducing plantar fibroblasts will induce the overlying keratinocytes to express plantar-specific keratins leading to a tougher epidermis. Using a computational finite element model of a weight-bearing residual limb, we estimate that skin deformation (a key driver of pressure ulcer injuries) could be halved by reprogramming skin to a plantar-like phenotype. We believe this strategy could yield new progress in pressure ulcer prevention for amputees, facilitating rehabilitation and improving quality of life for patients.

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.

Safety Assessment of Rehabilitation Robots: A Review Identifying Safety Skills and Current Knowledge Gaps

The assessment of rehabilitation robot safety is a vital aspect of the development process, which is often experienced as difficult. There are gaps in best practices and knowledge to ensure safe usage of rehabilitation robots. Currently, safety is commonly assessed by monitoring adverse events occurrence. The aim of this article is to explore how safety of rehabilitation robots can be assessed early in the development phase, before they are used with patients. We are suggesting a uniform approach for safety validation of robots closely interacting with humans, based on safety skills and validation protocols. Safety skills are an abstract representation of the ability of a robot to reduce a specific risk or deal with a specific hazard. They can be implemented in various ways, depending on the application requirements, which enables the use of a single safety skill across a wide range of applications and domains. Safety validation protocols have been developed that correspond to these skills and consider domain-specific conditions. This gives robot users and developers concise testing procedures to prove the mechanical safety of their robotic system, even when the applications are in domains with a lack of standards and best practices such as the healthcare domain. Based on knowledge about adverse events occurring in rehabilitation robot use, we identified multi-directional excessive forces on the soft tissue level and musculoskeletal level as most relevant hazards for rehabilitation robots and related them to four safety skills, providing a concrete starting point for safety assessment of rehabilitation robots. We further identified a number of gaps which need to be addressed in the future to pave the way for more comprehensive guidelines for rehabilitation robot safety assessments. Predominantly, besides new developments of safety by design features, there is a strong need for reliable measurement methods as well as acceptable limit values for human-robot interaction forces both on skin and joint level.

Quantitative iTRAQ LC-MS/MS reveals muscular proteome profiles of deep pressure ulcers

Pressure ulcers (PUs) are a common clinical issue lacking effective treatment and validated pharmacological therapy in hospital settings. Ischemia-reperfusion injury of deep tissue, especially muscle, plays a vital role in the formation and development of the overwhelming majority of PUs. However, muscular protein expression study in PUs has not been reported. Herein, we aimed to investigate the muscular proteins profiles in PUs and to explore the pathological mechanism of PUs. The iTRAQ LC-MS/MS was conducted to detect the protein profiles in clinical muscle samples of PUs. The GO and KEGG pathways analyses were performed for annotation of differentially expressed proteins. Protein-protein interaction (PPI) network was constructed by STRING online database, and hub proteins were validated by the immunoblotting. Based on proteomics results, we found a number of proteins that were differentially expressed in PU muscle samples compared with the normal and identified unique proteins expression patterns between these two groups, suggesting that they might involve in pathological process of the disease. Importantly, cathepsin B and D, as well as other autophagy-lysosome and apoptosis associated proteins were identified. Further experiments characterize the expression of these proteins and their regulation in the process of apoptosis and autophagy. These findings may provide novel insights into the mechanisms of lysosome-associated pathways involved in the initiation of PUs. This is the first study linking proteomics to PUs muscle tissues, which indicated cathepsin B and D might be key drug target for PUs.

Effect of Hospital Linens on Unit-Acquired Pressure Injuries for Adults in Medical ICUs: A Cluster Randomized Controlled Trial

Objectives:

Researchers have shown in laboratory studies that different types of fabrics were associated with changes in skin moisture, friction, shear, and temperature that may predispose patients to pressure injury. There was an association between type of fiber used in hospital linens and pressure injury development in previous clinical studies. We examined if bed linens made from a newly developed synthetic fiber fabric affected occurrence rate, time to development, and severity of unit-acquired pressure injury in critically ill adult inpatients.

Design:

Cluster randomized controlled trial.

Setting:

Five adult medical ICUs within one quaternary care center in the Midwest United States.

Patients:

Patients were assigned to a unit based on bed availability. In total, there were 3,332 patients in the study.

INTERVENTIONS:

Participating medical ICUs were randomly assigned to cotton fiber or synthetic fiber linens for the first 6 months of the study period, and assignment reversed after a 14-day washout period for the final 6 months.

Measurements and Main Results:

Unit-acquired pressure injury occurrence rate, time to first unit-acquired pressure injury, and severity were evaluated using generalized mixed effect models with patient as a random effect, and a marginal Cox proportional hazards model with repeated admissions from the same patient accounted for by use of a sandwich estimator of the variance. There were 1,706 patients on cotton fiber linens and 1,626 patients on synthetic fiber linens. Groups were similar on demographics except race and admitting diagnosis groupings. Occurrence rate (p = 0.99), time to development (p = 0.99), and maximum severity of unit-acquired pressure (p = 0.86) were similar between groups before and after controlling for race and admitting diagnosis groupings.

Conclusions:

Linen type did not affect unit-acquired pressure injury occurrence rate, severity, or timing. Standard unit-acquired pressure injury prevention efforts may be more cost-effective than investment in synthetic fiber linens.

A Soft Pressure Sensor Skin to Predict Contact Pressure Limit Under Hand Orthosis

Customized static orthoses in rehabilitation clinics often cause side effects, such as discomfort and skin damage due to excessive local contact pressure. Currently, clinicians adjust orthoses to reduce high contact pressure based on subjective feedback from patients. However, the adjustment is inefficient and prone to variability due to the unknown contact pressure distribution as well as differences in discomfort due to pressure across patients. This paper proposed a new method to predict a threshold of contact pressure (pressure limit) associated with moderate discomfort at each critical spot under hand orthoses. A new pressure sensor skin with 13 sensing units was configured from FEA results of pressure distribution simulated with hand geometry data of six healthy participants. It was used to measure contact pressure under two types of customized orthoses for 40 patients with bone fractures. Their subjective perception of discomfort was also measured using a 6 scores discomfort scale. Based on these data, five critical spots were identified that correspond to high discomfort scores (>1) or high pressure magnitudes (>0.024 MPa). An artificial neural network was trained to predict contact pressure at each critical spot with orthosis type, gender, height, weight, discomfort scores and pressure measurements as input variables. The neural networks show satisfactory prediction accuracy with R² values over 0.81 of regression between network outputs and measurements. This new method predicts a set of pressure limits at critical locations under the orthosis that the clinicians can use to make orthosis adjustment decisions.

A randomized controlled trial to compare the interface pressures of alternating pressure overlay with gel pad versus gel pad alone during prolonged surgery

INTRODUCTION

Prolonged surgery is a known risk of pressure ulcer formation. Pressure ulcers affect the quality of life, are a significant cause of morbidity and mortality, and pose a burden on the healthcare system. This study aimed to compare the effectiveness of an alternating pressure (AP) overlay with Gel pad against the Gel pad in reducing interface pressure (IP) during prolonged surgery.

METHODS

A total of 180 participants from a tertiary hospital were randomized to AP overlay with Gel pad group (n = 90) and Gel pad group (n = 90). Patients were placed supine on the pressure redistributing surfaces, and IP data under the sacrum and ischial tuberosities were collected at an interval of 30 min from 0 min up to a maximum of 570 min.

RESULTS

Based on data from 133 participants, the average IPs during all the deflation cycles of the AP overlay (with Gel pad) were significantly lower than the average continuous IP recorded for Gel pad throughout the measuring period (p < 0.001). Only three patients (2.26% of study participants) - Gel pad group (n = 2; 2.99%) and AP overlay with Gel pad group (n = 1; 1.52%) developed post-operative pressure ulcer (p = 0.5687).

CONCLUSIONS

The lower IP during deflation cycles of the AP overlay (with Gel pad) suggests its potential effectiveness in preventing pressure ulcer formation in patients undergoing prolonged surgery. The prevention and reduction of pressure ulcers will have a considerable impact on the improved quality of life and cost savings for the patient. The study findings may facilitate the formulation of policies for preventing pressure ulcer development in the perioperative setting.

Determination of Three-Dimensional Corrective Force in Adolescent Idiopathic Scoliosis and Biomechanical Finite Element Analysis

AIMS

In this study we have considered the three dimensional corrective forces for correction of scoliosis by using a patient specific finite element model.

MATERIALS AND METHODS

An objective function of corrective forces in three-dimensional space was defined. Computed tomography images were used to reconstruct three dimensional model of scoliotic trunk. Computer aided engineering software Abaqus was used to establish finite element model of deformed spine and its biomechanical characteristics were analyzed. By adjusting magnitude and position of corrective forces, objective function was minimized to achieve best orthopedic effect. The proposed corrective conditions were divided into three groups: (1) thoracic deformity; (2) lumbar deformity; (3) both thoracic and lumbar deformities were considered.

RESULTS

In all three cases, the objective function was reduced by 58, 52, and 63%, respectively. The best correction forces point was located on convex side of maximum displacement of vertebral body.

CONCLUSION

Using minimum objective function method, spinal deformity in three-dimensional space can be sufficiently reduced. This study provides scientific basis for design of a new corrective brace for treatment of scoliosis.

The relationship between pressure injury complication and mortality risk of older patients in follow-up: A systematic review and meta-analysis

Pressure injuries (PIs) have now become a common complication of the elderly patients. Some studies have observed that pressure injuries may increase mortality, but this area of evidence has not been evaluated and summarised. The aim of this study was to compare the mortality of patients with pressure injuries and those without pressure injuries. A meta-analysis of observational studies was performed. PubMed, Cochrane Library, Embase, and Web of Science were searched up to April 2019. Studies about mortality among the elderly patients with and without pressure injuries were included. Methodological quality was assessed by the Newcastle-Ottawa Scale (NOS). The fixed effect or random effect model was determined by the test of heterogeneity. The subgroup analysis was performed based on the pressure injuries stages, the region, and the type of study design. The meta-regression analysis was performed to investigate the relationship between the mortality and patients' enrolled year, average age, the incidence of pressure injuries, and gender ratio. The sensitivity analysis was used to explore the impact of an individual study by excluding one at a time. The hazard ratio (HR) and 95% confidence intervals (CIs) in terms of the comparison of two groups were extracted for meta-analysis. A survival curve between two groups by individual patient-level was drew. Eight studies with 5523 elderly patients were included in the analysis. Follow-up periods for the included studies ranged from about 0.5 to 3 years. The elderly patients who complicated with pressure injuries had a higher risk of death. The pooled HR was 1.78 (95% CI 1.46-2.16). A funnel plot showed no publication bias. Further subgroup analysis showed that HR values for the patient stage 3 to 4 pressure injuries (HR:2.41; 95% CI:1.08-5.37) were higher than stage 1-4 and 2-4 pressure injuries (HR: 1.66; 95% CI: 1.35-2.05; HR: 1.74; 95% CI: 1.16-2.60). The meta-regression analysis found that patients' enrolled year, average age, the incidence of pressure injuries, and gender ratio were not the sources of heterogeneity. Sensitivity analyses showed that the outcomes of the study did not change after removing the Onder's article. The survival curve at the individual patient-level also indicated that patients complicated with pressure injuries significantly increased the risk of death (HR: 1.958; 95% CI: 1.79-2.14) in elderly patients. Our meta-analysis indicated that patients complicated with pressure injuries are estimated to have a two times higher risk on mortality compared with patients without pressure injuries during the 3 years follow-up period. Particular attention should be given to the elderly patients who are at higher risk for mortality.

Modifiable patient-related factors associated with pressure ulcers on the sacrum and heels: Secondary data analyses

AIM

To explore factors associated with the presence of category I-IV pressure ulcers on the sacrum and heels.

DESIGN

Cross-sectional, secondary data analysis using data collected from the Landelijke Prevalentiemeting Zorgproblemen (LPZ) project, a multicentre prevalence study including nursing home residents and community care clients (N = 4,842) in the Netherlands in 2017.

METHODS

A single binary logistic regression model was designed to identify factors associated with the presence of pressure ulcers. Additionally, a multiple binary logistic regression model including modifiable explanatory factors associated with the presence of pressure ulcers was designed.

RESULTS

Impaired mobility, friction and shear (evaluated using the Braden Scale) are significantly associated with the presence of both sacral and heel category I-IV pressure ulcers. Incontinence-associated dermatitis is significantly associated with category I-IV sacral pressure ulcers.

CONCLUSION

In pressure ulcer prevention, nursing interventions should focus on frequent repositioning and mobilization while avoiding exposure of the skin to friction and shear. The need to consider incontinence-associated dermatitis, incontinence and moisture as important factors in pressure ulcer risk assessment is confirmed.

IMPACT

Pressure ulcers occur when skin and tissues are deformed between bony prominences and the support surface in a sitting or lying position. They are the result of a complex interaction between direct causal factors and a wide range of indirect factors. Recognition of these factors influences risk assessment guidance and practice. Knowledge of skin-specific factors at the patient level, modifiable by nursing interventions, enables a better targeted and tailored preventive approach.

Why is the heel particularly vulnerable to pressure ulcers?

In this article, the vulnerability of the soft tissues of the heel to pressure ulcers (injuries) is explained from a biomechanical engineering perspective, and emerging technologies for protecting the heel, particularly low-friction garments, are reviewed. Sustained deformations in the soft tissue of the weight-bearing posterior heel cause progressive cell and tissue damage due to loss of homeostasis in the cells, as the cytoskeleton and plasma membranes of the affected cells lose integrity and functionality. This deformation damage onsets and evolves rapidly when there is no relief of the tissue distortion (e.g. in supine motionless lying). Hence, prevention should be timely and be applied across all patient populations that are at risk. In particular there is a need to protect tissues from the action of frictional forces that are shearing not only the skin but also the deep tissue structures of the heel. The internal anatomy and physiology of the posterior heel, the common hospital conditions (lying supine, head of the bed elevated) and medical conditions involving neuropathy and perfusion impairments may impose specific risk for heel (pressure) ulcers. There is growing evidence that low-friction-fabric garments may provide added benefits in preventing heel ulcers when used in addition to standard clinical and technology-supported pressure ulcer prevention strategies, as the low-friction fabric structures absorb frictional forces before these are able to considerably distort the susceptible heel tissues.

On skin microrelief and the emergence of expression micro-wrinkles

Over the course of a life time, as a result of adaptive mechanobiological processes (e.g. ageing), or the action of external physical factors such as mechanical loading, the human skin is subjected to, and hosts complex biophysical processes. These phenomena typically operate through a complex interplay, that, ultimately, is responsible for the evolutive geometrical characteristics of the skin surface. Wrinkles are a manifestation of these effects. Although numerous theoretical models of wrinkles arising in multi-layered structures have been proposed, they typically apply to idealised geometries. In the case of skin, which can be viewed as a geometrically complex multi-layer assembly, it is pertinent to question whether the natural skin microrelief could play a significant role in conditioning the characteristics of compression-induced micro-wrinkles by acting as an array of geometrical imperfections. Here, we explore this question through the development of an anatomically-based finite strain parametric finite element model of the skin, represented as a stratum corneum layer on top of a thicker and softer substrate. Our study suggests that skin microrelief could be the dominant factor conditioning micro-wrinkle characteristics for moderate elastic modulus ratios between the two layers. Beyond stiffness ratios of 100, other factors tend to overwrite the effects of skin microrelief. Such stiffness ratio fluctuations can be induced by changes in relative humidity or particular skin conditions and can therefore have important implications for skin tribology.

Suppression of LRRC19 promotes cutaneous wound healing in pressure ulcers in mice

The ischemia-reperfusion (I/R) induced skin lesion has been identified as primary cause of pressure ulcer. Better understanding of the mechanism is required for new therapy development. Leucine rich repeat containing protein 19 (LRRC19) is a recently discovered transmembrane protein containing leucine-rich repeats and plays a role in immune response. To investigate the role of LRRC19 in pressure ulcers, mouse ulcer model was established with two cycles of I/R. The expression of LRRC19 was assessed during injury. siRNA mediated LRRC19 downregulation was applied to investigate the disease severity, immune cell infiltration and pro-inflammatory cytokines production. The primary skin fibroblasts were stimulated with IL-1β to dissect the molecular mechanism. LRRC19 was readily induced in I/R induced lesion site in a pattern mimicking the disease progress as measured by wound area. Knockdown of LRRC19 by siRNA significantly alleviated the disease severity and attenuated immune cell infiltration and pro-inflammatory cytokines production. In primary skin fibroblast model, siRNA knockdown of LRRC19 suppressed IL-1β mediated NFκB activation and its downstream cytokines production. LRRC19 was a novel factor for I/R-induced tissue damage by promoting NFκB dependent pro-inflammatory response. Our results supported that LRRC19 could be a potential therapeutic target for pressure ulcers.

Pressure ulcers in critically ill patients - Preventable by non-sedation? A substudy of the NONSEDA-trial

OBJECTIVE

Pressure ulcers still pose a significant clinical challenge to critically ill patients. This study is a substudy of the multicenter NONSEDA-trial, where critically ill patients were randomised to sedation or non-sedation during mechanical ventilation. The objective of this substudy was to assess if non-sedation affected the occurrence of pressure ulcers.

DESIGN

Retrospective assessment of data from a single NONSEDA-trial site.

SETTING

Mixed intensive care unit.

OUTCOME MEASURES

The occurrence of pressure ulcers, described by grade and location.

RESULTS

205 patients were included. Patients with pressure ulcers in the two groups were comparable with regards to baseline data. There were 44 ulcers in 32 patients in the sedated group and 31 ulcers in 25 patients in the non-sedated group (p=0.08). 64% of the ulcers in sedated patients were located on sacrum and heels, whereas 68% of the ulcers in non-sedated patients were related to equipment (p=0.03).

CONCLUSIONS

Non-sedation did not significantly reduce the number of pressure ulcers. Non-sedation significantly affected the location of ulcers: non-sedated patients mainly had ulcers related to equipment, whereas sedated patients mainly had ulcers on the sacrum and heels.