How do microclimate factors affect the risk for superficial pressure ulcers: A mathematical modeling study

Evaluating the accuracy of impaired skin integrity in critically ill patients: Key characteristics and clinical implications

OBJECTIVE

To evaluate the accuracy of the defining characteristics of the nursing diagnosis Impaired skin integrity (00046) in patients admitted to intensive care units (ICUs).

METHODS

A cross-sectional diagnostic accuracy study was conducted with 105 adult patients admitted to an ICU. A latent class model with random effects was used to test the sensitivity and specificity of the defining characteristics investigated. The diagnosis Impaired skin integrity (00046) was the dependent variable, whereas sociodemographic and clinical data were the independent variables.

RESULTS

Impaired skin integrity was present in 3.75% of the sample. The defining characteristic with the best accuracy for the diagnosis was dry skin, with high sensitivity (0.9994) and specificity (0.9106). Other characteristics stood out in terms of sensitivity measures: altered skin color (0.9994) and foreign matter piercing skin (0.9994). In terms of specificity, the following stood out: desquamation (1.000), localized area hot to touch (0.9901), pruritus (0.9897), bleeding (0.9802), and hematoma (0.9208).

CONCLUSION

The defining characteristics that helped infer the diagnosis Impaired skin integrity (00046) with greater certainty were dry skin, altered skin color, foreign matter piercing skin, desquamation, localized area hot to touch, pruritus, bleeding, and hematoma.

IMPLICATIONS FOR NURSING PRACTICE

Identifying defining characteristics with high diagnostic accuracy for Impaired skin integrity (00046) enables nurses to expand their clinical perspective on this dysfunction, which can affect the skin of critically ill patients, and to develop individualized care plans.

Understanding occipital pressure sores in UK military casualties: a pilot study in healthy military personnel

INTRODUCTION

The high prevalence of occipital ulcers in UK military casualties observed during the conflict in Afghanistan is a multifactorial phenomenon. However, the consensus is that ulceration is triggered by excessive pressure that is maintained for too long during the use of the general service military stretcher. Thresholds for capillary occlusion are accepted benchmarks to define excessive pressure, but similar thresholds for safe/excessive duration of pressure application do not exist. To address this gap in knowledge, we propose to use the time it takes for a healthy person to feel pain at the back of the head as an initial indication of safe exposure to pressure.

METHODS

Healthy military personnel (16 male/10 female) were asked to lie motionless on a typical general service stretcher until they felt pain. Time-to-pain and the location of pain were recorded. To support the interpretation of results, baseline sensitivity to pain and pressure distribution at the back of the head were also measured. Independent samples t-test was used to assess differences between genders.

RESULTS

Twenty participants felt pressure-induced soft-tissue pain at the back of the head. The remaining six participants terminated the test due to musculoskeletal pain caused by poor ergonomic positioning. On average, pain at the occiput developed after 31 min (±14 min). Female participants were significantly more sensitive to pain (t(24)=3.038,p=0.006), but time-to-pain did not differ significantly between genders (p>0.05).

CONCLUSIONS

When people lie motionless on a typical military stretcher, the back of the head is the first area of the body that becomes painful due to pressure. The fact that pain develops in ≈30 min can help healthcare providers decide how frequently to reposition their patients who are unable to do this on their own. More research is still needed to directly link time-to-pain with time-to-injury.

The complex interplay between mechanical forces, tissue response and individual susceptibility to pressure ulcers

OBJECTIVE

The most recent edition of the International Clinical Practice Guideline for the Prevention and Treatment of Pressure Ulcers/Injuries was released in 2019. Shortly after, in 2020, the first edition of the SECURE Prevention expert panel report, focusing on device-related pressure ulcers/injuries, was published as a special issue in the Journal of Wound Care. A second edition followed in 2022. This article presents a comprehensive summary of the current understanding of the causes of pressure ulcers/injuries (PU/Is) as detailed in these globally recognised consensus documents.

METHOD

The literature reviewed in this summary specifically addresses the impact of prolonged soft tissue deformations on the viability of cells and tissues in the context of PU/Is related to bodyweight or medical devices.

RESULTS

Prolonged soft tissue deformations initially result in cell death and tissue damage on a microscopic scale, potentially leading to development of clinical PU/Is over time. That is, localised high tissue deformations or mechanical stress concentrations can cause microscopic damage within minutes, but it may take several hours of continued mechanical loading for this initial cell and tissue damage to become visible and clinically noticeable. Superficial tissue damage primarily stems from excessive shear loading on fragile or vulnerable skin. In contrast, deeper PU/Is, known as deep tissue injuries, typically arise from stress concentrations in soft tissues at body regions over sharp or curved bony prominences, or under stiff medical devices in prolonged contact with the skin.

CONCLUSION

This review promotes deeper understanding of the pathophysiology of PU/Is, indicating that their primary prevention should focus on alleviating the exposure of cells and tissues to stress concentrations. This goal can be achieved either by reducing the intensity of stress concentrations in soft tissues, or by decreasing the exposure time of soft tissues to such stress concentrations.

Exploring body morphology, sacral skin microclimate and pressure injury development and risk among patients admitted to an intensive care unit: A prospective, observational study

OBJECTIVE

To determine the association between body morphology, sacral skin microclimate and their impact on the development and risk of pressure injuries among patients in an intensive care unit.

METHODOLOGY

A prospective observational exploratory study was conducted over 30 weeks. Repeat study observations occurred multiple times a week for 28 days or until discharge. Participant inclusion criteria were ≥ 18 years of age, expected intensive care length of stay > 24 h and intact skin over the sacrum region.

SETTING

The study was conducted in a 36-bed intensive care unit of a major metropolitan public hospital in Queensland, Australia.

OUTCOME MEASURES

Pressure injuries were staged and independently verified according to the international pressure injury classification system. Pressure injury risk was determined by the Braden scale score and subepidermal oedema, using a subepidermal moisture scanner at the sacrum.

RESULTS

Of the 93 participants recruited, an inverted triangle body shape (p =.049), a BMI > 25 kg/m2 (p =.008), a standard foam mattress type (p =.017) and increased length of stay (p <.001) were associated with an increased pressure injury risk according to subepidermal oedema. Participants with increased sacral skin temperature (p <.001), mechanical ventilation (p <.001), vasoactive drugs administered (p =.003), increased sequential organ failure assessment score (p =.047), neurovascular diagnosis (p =.031) and increased length of stay (p =.027) were associated with increased pressure injury risk according to the Braden scale score.

CONCLUSION

Body morphology and skin microclimate are associated with pressure injury risk during critical illness.

IMPLICATIONS FOR CLINICAL PRACTICE

Subepidermal oedema was associated with a patient's shape, body mass index and mattress type, factors that directly influence the pressure loading and the skin, whereas the Braden scale was associated with sacral temperature and clinical measures of critical illness. Consideration of body morphology and skin microclimate in pressure injury risk assessment could lead to more specific prevention strategies targeting high risk patients.

Strategies in surface engineering for the regulation of microclimates in skin-medical product interactions

There is a growing number of personal healthcare devices that are in prolonged contact with the skin. The functionality of these products is linked to the interface formed by the contact between the medical apparatus and the skin. The interface can be characterised by its topology, compliance, and moisture and thermal regulating capabilities. Many devices are, however, described to have suboptimal and occlusive contacts, resulting in physiological unfavourable microclimates at the interface. The resulting poor management of moisture and temperature can impact the functionality and utility of the device and, in severe cases, lead to physical harm to the user. Being able to control the microclimate is therefore expected to limit medical-device related injuries and prevent associated skin complications. Surface engineering can modify and potentially enhance the regulation of the microclimate factors surrounding the interface between a product's surface and the skin. This review provides an overview of potential engineering solutions considering the needs for, and influences on, regulation of temperature and moisture by considering the skin-medical device interface as a system. These findings serve as a platform for the anticipated progress in the role of surface engineering for skin-device microclimate regulation.

Testing the effectiveness of a polymeric membrane dressing in modulating the inflammation of intact, non-injured, mechanically irritated skin

We investigated the inflammatory (IL-1 alpha) and thermal (infrared thermography) reactions of healthy sacral skin to sustained, irritating mechanical loading. We further acquired digital photographs of the irritated skin (at the visible light domain) to assess whether infrared imaging is advantageous. For clinical context, the skin status was monitored under a polymeric membrane dressing known to modulate the inflammatory skin response. The IL-1 alpha and infrared thermography measurements were consistent in representing the skin status after 40 min of continuous irritation. Infrared thermography overpowered conventional digital photography as a contactless optical method for image processing inputs, by revealing skin irritation trends that were undetectable through digital photography in the visual light, not even with the aid of advanced image processing. The polymeric membrane dressings were shown to offer prophylactic benefits over simple polyurethane foam in the aspects of inflammation reduction and microclimate management. We also concluded that infrared thermography is a feasible method for monitoring the skin health status and the risk for pressure ulcers, as it avoids the complexity of biological marker studies and empowers visual skin assessments or digital photography of skin, both of which were shown to be insufficient for detecting the inflammatory skin status.

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.

Skin hydration measurement and the prediction of the early development of pressure ulcers among at risk adults: A systematic review

This systematic review aimed to examine skin hydration and determine if this biophysical parameter can predict pressure ulcer development in at risk adults. A literature search was conducted in March 2022, using PubMed, CINAHL, SCOPUS, Cochrane, and EMBASE databases. A total of 1727 records were returned, with 9 studies satisfying the inclusion criteria. Data were extracted using a pre-designed extraction tool and a narrative synthesis of the data was undertaken. The methodological quality of the included articles was assessed using the evidence-based librarianship checklist. Included studies were published between 1997 and 2021, with most using a prospective cohort design (88.9%, n = 8). The mean sample size was 74 participants (SD = 38.6; median 71). All studies measured skin hydration objectively, with 55.6% (n = 5) using the Corneometer® CM825 and 33.3% (n = 3) of studies reported a statistically significant association between skin hydration and pressure ulcer development. The mean evidence-based librarianship percentage was 66.6% (SD: 20.7%), however, only 33.3% (n = 3) of studies scored ≥75%, indicating validity. The quality of included studies, methodology variation, and reported results has reduced the homogeneity of outcomes. This review highlights the requirement for future research evidence to ascertain the role of skin hydration in pressure ulcer development.

Biomechanical and Physiological Evaluation of Respiratory Protective Equipment Application

Purpose

Respiratory protective equipment is widely used in healthcare settings to protect clinicians whilst treating patients with COVID-19. However, their generic designs do not accommodate the variability in face shape across genders and ethnicities. Accordingly, they are regularly overtightened to compensate for a poor fit. The present study aims at investigating the biomechanical and thermal loads during respirator application and the associated changes in local skin physiology at the skin–device interface.

Materials and Methods

Sixteen healthy volunteers were recruited and reflected a range of gender, ethnicities and facial anthropometrics. Four single-use respirators were evaluated representing different geometries, size and material interfaces. Participants were asked to wear each respirator in a random order while a series of measurements were recorded, including interface pressure, temperature and relative humidity. Measures of transepidermal water loss and skin hydration were assessed pre- and post-respirator application, and after 20 minutes of recovery. Statistical analysis assessed differences between respirator designs and associations between demographics, interface conditions and parameters of skin health.

Results

Results showed a statistically significant negative correlation (p < 0.05) between the alar width and interface pressures at the nasal bridge, for three of the respirator designs. The nasal bridge site also corresponded to the highest pressures for all respirator designs. Temperature and humidity significantly increased (p < 0.05) during each respirator application. Significant increases in transepidermal water loss values (p < 0.05) were observed after the application of the respirators in females, which were most apparent at the nasal bridge.

Conclusion

The results revealed that specific facial features affected the distribution of interface pressures and depending on the respirator design and material, changes in skin barrier function were evident. The development of respirator designs that accommodate a diverse range of face shapes and protect the end users from skin damage are required to support the long-term use of these devices.

The skin microbiome of infected pressure ulcers: A review and implications for health professionals

BACKGROUND

Pressure ulcers (PUs) are injuries resulting from ischaemia caused by prolonged compression or shear forces on the skin, adjacent tissues and bones. Advanced stages of PUs are associated with infectious complications and constitute a major clinical challenge, with high social and economic impacts in health care.

GOALS

This study aims to identify and describe the relationship between PU risk factors, stages and anatomical locations, and the relevance of microbial cohabitation and biofilm growth.

METHODS

The narrative review method to advocating a critical and objective analysis of the current knowledge on the topic was performed. Indexed databases and direct consultation to specialized and high-impact journals on the subject were used to extract relevant information, guided by co-authors. The Medical Subject Headings of pressure ulcer (or injury), biofilms, infection and other analogues terms were used.

RESULTS

Development of PUs and consequent infection depends on several direct and indirect risk factors, including cutaneous/PU microbiome, microclimate and behavioural factors. Infected PUs are polymicrobial and characterized by biofilm-associated infection, phenotypic hypervariability of species and inherent resistance to antimicrobials. The different stages and anatomical locations also play an important role in their colonization. The prevention and monitoring of PUs remain crucial for avoiding the emergence of systemic infections and reducing health care-associated costs, improve the quality of life of patients and reduce the mortality-associated infected PUs.

A novel mathematical model including the wetness parameter as a variable for prevention of pressure ulcers

Pressure ulcers are injuries caused by external conditions such as pressure, friction, shear, and humidity resulting from staying in the same position for a long time in bedridden patients. It is a serious problem worldwide when assessed in terms of hospital capacity, nursing staff employment and treatment costs. In this study, we developed a novel mathematical model based on one of our previous models to prevent pressure ulcers or delay injuries. The proposed model uses a human thermal model that includes skin temperature, hypothalamus temperature, regional perspiration coefficient, and unconsciously loss of water amount. Moreover, in our model, we defined a variable wetness parameter in addition to the parameters, pressure, temperature, and humidity. The proposed model is mathematically defined in detail and tested for a wide range of parameters to show the model's effectiveness in determining the pressure ulcer formation risk. The model is also compared with a model from the literature that based on only the general parameters, pressure, temperature, and humidity. The obtained results showed that the model determines the risk of the occurrence of the pressure ulcer more precisely than the compared one.

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.

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.

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.

Keeping Patients Under the Damage Threshold for Pressure Injury: Addressing Microclimate Through Allostasis

BACKGROUND

Pressure injuries (PI) are an ongoing problem in health care. Current interventions, both from clinicians and support surface technologies, do not sufficiently address PI prevention.

PROBLEM

Patient microclimate is a contributing risk factor for PI, one which can be more adequately addressed. However, the acceptable range for microclimate is unknown, in part because the body adapts to changing conditions.

APPROACH

Two key concepts in allostasis are finite resources and responding to intrinsic and extrinsic demands. These concepts have not previously been applied to PI treatment or interventions. Addressing microclimate, when coupled with an increasing awareness of the cumulative effect of individual patient risk factors, can help resolve the risk of PI by lowering the cumulative inputs to keep patients under the threshold for tissue damage.

CONCLUSION

This new approach, which places microclimate risk into the broader conceptual framework of allostasis, can produce more effective products and interventions to prevent PI.

Brief intermittent pressure off-loading on skin microclimate in healthy adults - A descriptive-correlational pilot study

AIM

This study examined microclimate changes to the skin as a result of pressure over a 1 h period. The results were compared to skin parameter results following brief consecutive off-loading of pressure-prone areas.

DESIGN

A descriptive-correlational pilot study was undertaken.

METHOD

A convenience sample of 41 healthy adults aged 18-60 years was recruited. Participants engaged in four 1 h data collection sessions. The sessions were conducted in both semi-recumbent and supine positions. Measures of erythema, melanin, stratum corneum hydration, and skin temperature were taken at pressure-prone areas at baseline and after 1 h in an uninterrupted method (continuous pressure-loading) and every 10 min in an interrupted method (brief off-loading). The Corneometer and Mexameter (Courage + Khazaka Electronics GMbH, 2013) and Exergen DermaTemp DT-1001 RS Infrared Thermographic Scanner (Exergen Corporation, 2008) provided a digital appraisal of skin parameters. Intraclass correlation coefficients (ICC) were calculated to indicate test-retest reliability and absolute agreement of results between the two methods.

RESULTS

Strong agreement between the interrupted and uninterrupted method was observed with ICCs ranging from 0.72 to 0.99 (supine) and 0.62-0.99 (semi-recumbent). Endpoint measures tended to be higher compared to baseline measures for all skin parameters. Differences in skin parameters results by anatomical location were evident particularly for erythema and stratum corneum hydration; the elbows and heels yielded lower scores compared to the sacrum. Erythema had the most variation across methods. The supine and semi-recumbent positions had negligible effect on measured skin parameters.

CONCLUSIONS

Minimal variation between skin parameter results indicates that brief off-loading in the interrupted method did not significantly change the outcomes; minor shifts in positioning do not alter changes to the skin from pressure. Skin parameters varied by anatomical location and changed over a 1 h period of pressure-loading.

RELEVANCE TO CLINICAL PRACTICE

Biophysical techniques may be able to assist accurate assessment of skin microclimate and skin colour. As brief off-loading (interruptions) to enable skin parameter measurement does not alter skin readings, researchers can proceed with some confidence regarding the use of this protocol in future studies assessing skin parameters. This study data provides a library of cutaneous changes at pressure-prone areas of healthy adults and is expected to inform innovative approaches to pressure injury risk assessment.

Review of Measuring Microenvironmental Changes at the Body-Seat Interface and the Relationship between Object Measurement and Subjective Evaluation

Being seated has increasingly pervaded both working and leisure lifestyles, with development of more comfortable seating surfaces dependent on feedback from subjective questionnaires and design aesthetics. As a consequence, research has become focused on how to objectively resolve factors that might underpin comfort and discomfort. This review summarizes objective methods of measuring the microenvironmental changes at the body–seat interface and examines the relationship between objective measurement and subjective sensation. From the perspective of physical parameters, pressure detection accounted for nearly two thirds (37/54) of the publications, followed by microclimatic information (temperature and relative humidity: 18/54): it is to be noted that one article included both microclimate and pressure measurements and was placed into both categories. In fact, accumulated temperature and relative humidity at the body–seat interface have similarly negative effects on prolonged sitting to that of unrelieved pressure. Another interesting finding was the correlation between objective measurement and subjective evaluation; however, the validity of this may be called into question because of the differences in experiment design between studies.

Dressing interventions to heal pressure ulcers: A protocol for an overview of systematic reviews and meta-analysis

BACKGROUND

Pressure ulcer (PU) is defined as a lesion or trauma to the skin and underlying tissue resulting from unrelieved pressure, shear, friction, moisture, or a combination of all these, usually appearing over a bony prominence. We aim to evaluate the credibility of systematic reviews and meta-analyses that assess the effectiveness, safety, and economy of the dressing treatments for PU through an overview.

METHODS

We searched the following electronic bibliographic databases: PubMed, Embase, Cochrane Library, CINAHL Complete, PsycARTICLES, PsycINFO, DynaMed Plus, as well as the Chinese databases without any language restriction. We will include meta-analyses that dressings treatments in the management of PUs. For each meta-analysis, we will estimate the effect size of a treatment through the random-effect model and the fixed-effect model, and we will evaluate between-study heterogeneity (Cochrane's Q and I statistics) and small-study effect (Egger's test); we will also estimate the evidence of excess significance bias. Methodological quality of each meta-analysis will be evaluated by using Assessment of Multiple Systematic Reviews 2.

RESULTS

This study is ongoing and the results will be submitted to a peer-reviewed journal for publication.

ETHICS AND DISSEMINATION

Ethical approval is not applicable, since this is an overview based on published articles.

PROTOCOL REGISTRATION NUMBER

The protocol has been registered on PROSPERO under the number CRD42020161232.

Use of a Support Surface Standard to Test the Effects of a Turning and Positioning Device Versus Low-Air-Loss Therapy on Temperature and Humidity

BACKGROUND

Turning and repositioning devices (TRDs) help to reduce strain on caregivers, but clinicians question their effects on humidity and temperature (microclimate) at the skin surface that may increase risk of pressure ulcers.

OBJECTIVE

To pilot the use of a standard test for support surfaces to compare microclimate at the skin surface in three scenarios: (1) on a low-air-loss (LAL) surface, (2) on a representative TRD with a basic underpad (TRDU) placed on a LAL surface, and (3) on a negative control with full occlusion. The results are designed to inform clinical decision-making in using a TRD on a LAL surface and the viability of using this test to study TRDs.

DESIGN

Measuring humidity and temperature at the device-surface interface using a heated moisture-exuding bronze thermodynamic human model in a laboratory setting.

MAIN OUTCOME MEASURE

Humidity and temperature levels across 3 hours 15 minutes of continuous loading with a 45-second complete unloading to simulate a position change at 3 hours.

MAIN RESULTS

Relative humidity on the TRDU was below that on the LAL surface for the first 110 minutes and was markedly lower than the negative control for the remainder of humidity testing. Temperature on the TRDU was well below the negative control and negligibly higher than the surface alone throughout testing. The position change enhanced the effects of the TRDU.

CONCLUSIONS

The support surface standard test appears useful in evaluating TRDs. This TRD along with the basic underpad is more comparable to a LAL surface than to full occlusion in managing the microclimate of the skin and pressure ulcer risk.

WUWHS 2020 Global Healing Changing Lives, Abu Dhabi, UAE March 8-12

The abstract book contains the abstracts of keynote lectures, global gelebration, focus sessions, symposia, regional view, workshops, sponsored symposia, oral presentations, posters and the index.

Indentation marks, skin temperature and comfort of two cervical collars: A single-blinded randomized controlled trial in healthy volunteers

BACKGROUND

Collar-related pressure ulcers (CRPU) are a problem in trauma patients with a suspicion of cervical cord injury patients. Indentation marks (IM), skin temperature (T_sk) and comfort could play a role in the development of CRPU. Two comparable cervical collars are the Stifneck® and Philadelphia®. However, the differences between them remain unclear.

AIM

To determine and compare occurrence and severity of IM, T_sk and comfort of the Stifneck® and Philadelphia® in immobilized healthy adults.

METHODS

This single-blinded randomized controlled trial compared two groups of immobilized participants in supine position for 20 min.

RESULTS

All participants (n = 60) generated IM in at least one location in the observed area. Total occurrence was higher in the Stifneck®-group (n = 95 versus n = 69; p = .002). T_sk increased significantly with 1.0  °C in the Stifneck®-group and 1.3 °C in the Philadelphia®-group (p = .024). Comfort was rated 3 on a scale of 5 (p = .506).

CONCLUSION

The occurrence of IM in both groups was high. In comparison to the Stifneck®, fewer and less severe IM were observed from the Philadelphia®. The T_sk increased significantly with both collars; however, no clinical difference in increase of T_sk between them was found. The results emphasize the need for a better design of cervical collars regarding CRPU.

The bioengineering theory of the key modes of action of a cyanoacrylate liquid skin protectant

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

The microclimate under dressings applied to intact weight-bearing skin: Infrared thermography studies

BACKGROUND

When a patient is lying in a hospital bed (e.g. supine or prone), bodyweight forces distort soft tissues by compression, tension and shear, and may lead to the onset of pressure ulcers in those who are stationary and insensate, especially at their pelvic region. Altered localized microclimate conditions, particularly elevated skin temperatures leading to perspiration and resulting in skin moisture or wetness, are known to further increase the risk for pressure ulcers, which is already high in immobile patients.

METHODS

We have used infrared thermography to measure local skin temperatures at the buttocks of supine healthy subjects, to quantitatively determine, for the first time in the literature, how skin microclimate conditions associated with a weight-bearing Fowler's position are affected by application of dressings. Our present methodology has been applied to compare a polymeric membrane dressing versus placebo foam, with a no-dressing case used as reference.

FINDINGS

One hour of lying in a Fowler's position was already enough to cause considerable heat trapping (~3 °C rise) between the weight-bearing body and the support surface. Analyses of normalized local skin temperatures and entropy of the temperature distributions indicated that the polymeric membrane dressing material allowed better and more homogenous clearance of locally accumulated body-heat with respect to simple foam.

INTERPRETATION

Infrared thermography is suitable for characterizing skin microclimate conditions under different dressings, and, accordingly, is effective in developing and evaluating pressure ulcer prevention and treatment strategies - both of which require adequate skin microclimate.

The cutaneous microbiome in hospitalized patients with pressure ulcers

This study investigated whether there are differences in the composition of the cutaneous microbiome of the unaffected skin between patients with pressure ulcers compared with those without pressure ulcers. The cutaneous microbiome of the unaffected skin of 15 patients with sacral pressure ulcers compared to 15 patients without pressure ulcers was analysed. It demonstrated that the inter-individual variation in skin microbiota of patients with pressure ulcers was significantly higher (P = 0.01). The abundance of 23 species was significantly different with Staphylococcus aureus and unclassified Enterococcus the most abundant species in patients with pressure ulcers. Random Forest models showed that eight species were associated with pressure ulcers occurrence in 81% of the patients. A subset of four species gave the strongest interaction. The presence of unclassified Enterococcus had the highest association with pressure ulcer occurrence. This study is the first to demonstrate that the cutaneous microbiome is altered in patients with pressure ulcers.

Is a simplified Finite Element model of the gluteus region able to capture the mechanical response of the internal soft tissues under compression?

BACKGROUND

Internal soft tissue strains have been shown to be one of the main factors responsible for the onset of Pressure Ulcers and to be representative of its risk of development. However, the estimation of this parameter using Finite Element (FE) analysis in clinical setups is currently hindered by costly acquisition, reconstruction and computation times. Ultrasound (US) imaging is a promising candidate for the clinical assessment of both morphological and material parameters.

METHOD

The aim of this study was to investigate the ability of a local FE model of the region beneath the ischium with a limited number of parameters to capture the internal response of the gluteus region predicted by a complete 3D FE model. 26 local FE models were developed, and their predictions were compared to those of the patient-specific reference FE models in sitting position.

FINDINGS

A high correlation was observed (R = 0.90, p-value < 0.01). A sensitivity analysis showed that the most influent parameters were the mechanical behaviour of the muscle tissues, the ischium morphology and the external mechanical loading.

INTERPRETATION

Given the progress of US for capturing both morphological and material parameters, these results are promising because they open up the possibility to use personalised simplified FE models for risk estimation in daily clinical routine.

Prediction of Diabetic Foot Ulceration: The Value of Using Microclimate Sensor Arrays

BACKGROUND

Accurately predicting the risk of diabetic foot ulceration (DFU) could dramatically reduce the enormous burden of chronic wound management and amputation. Yet, the current prognostic models are unable to precisely predict DFU events. Typically, efforts have focused on individual factors like temperature, pressure, or shear rather than the overall foot microclimate.

METHODS

A systematic review was conducted by searching PubMed reports with no restrictions on start date covering the literature published until February 20, 2019 using relevant keywords, including temperature, pressure, shear, and relative humidity. We review the use of these variables as predictors of DFU, highlighting gaps in our current understanding and suggesting which specific features should be combined to develop a real-time microclimate prognostic model.

RESULTS

The current prognostic models rely either solely on contralateral temperature, pressure, or shear measurement; these parameters, however, rarely reach 50% specificity in relation to DFU. There is also considerable variation in methodological investigation, anatomical sensor configuration, and resting time prior to temperature measurements (5-20 minutes). Few studies have considered relative humidity and mean skin resistance.

CONCLUSION

Very limited evidence supports the use of single clinical parameters in predicting the risk of DFU. We suggest that the microclimate as a whole should be considered to predict DFU more effectively and suggest nine specific features which appear to be implicated for further investigation. Technology supports real-time in-shoe data collection and wireless transmission, providing a potentially rich source of data to better predict the risk of DFU.

Skin temperature as a clinical parameter for nursing care: a descriptive correlational study

Objective:

To identify the skin temperature in different body areas of hospitalised individuals in the surgical unit, without risk of developing a pressure ulcer (PU).

Methods:

A descriptive, correlational and cross-sectional study, carried out May–October 2017, in a surgical unit of a university hospital in southern Brazil. Temperature was measured at the bony prominences including scapula, elbow, trochanters and heels, on both sides of the body, as well as occipital and sacral regions.

Results:

A total of 230 patients took part in the study. All regions of the body measured presented differences in temperatures. The sacral region presented the highest mean temperature (34.2±0.1°C). Patients (aged 18–59 years) had higher skin temperatures in the sacral region than older patients (aged 60–88 years). There was a symmetry in temperatures on both sides of the body. There was a low degree of correlation between age, room temperature, room humidity and skin temperature in some body regions.

Conclusion:

The study established mean values for skin temperature in specific body regions in patients without risk of developing a PU, hospitalised in a surgical unit. It also demonstrates how skin temperature can be used as a clinical parameter in practice to support the prevention of PUs.

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.

Tissue response to applied loading using different designs of penile compression clamps

Background: Penile compression devices (PCD) or clamps are applied to compress the urethra and prevent urinary incontinence (UI). PCDs are more secure and less likely to leak than pads, allowing men the opportunity to participate in short-term, vigorous activities. However, they are uncomfortable, can cause pressure ulcers (PU) and affect penile blood flow. No objective assessment of tissue health has been undertaken to assess and compare different PCD designs and to provide guidance on safe use.

Objective: This study was designed to evaluate existing PCDs in terms of their physiological response and potential for pressure-induced injury.

Design, setting and participants: Six men with post-prostatectomy UI tested four selected PCDs at effective pressures, in a random order, in a controlled laboratory setting.

Outcome measurements and statistical analysis: Using objective methods for assessing skin injury, PCDs were measured in situ for their effects on circulatory impedance, interface pressures and inflammatory response.

Results and limitations: There was evidence for PCD-induced circulatory impedance in most test conditions. Interface pressures varied considerably between both PCDs and participants, with a mean value of 137.4±69.7 mmHg. In some cases, penile skin was noted to be sensitive to loading with elevated concentration of the cytokine IL-1α after 10 mins wear, indicating an inflammatory response. IL-1α levels were restored to baseline 40 mins following PCD removal.

Conclusion: Skin health measures indicated tissue and blood flow compromise during the 50 mins of testing using all PCDs. Although there was an elevation in pro-inflammatory cytokines, PCDs did not cause sustained irritation and skin health measures recovered 40 mins after PCD removal. This research indicates that application of a clamp for one hour with an equal clamp free time before reapplication is likely to be safe. Longer periods are often recommended by manufacturers but have yet to be tested.

Exploring pressures, tissue reperfusion and body positioning: a pilot evaluation

OBJECTIVE

To assess the relationship in healthy adults and critically ill patients between: patient position, body mass index (BMI), patient body temperature, interface pressure (IP) and tissue reperfusion (TR). Also to determine the relationship in critically ill patients between: Sequential Organ Failure Assessment (SOFA) score, Braden Scale score for predicting pressure injury risk, Acute Physiology and Chronic Health Evaluation II (APACHE II) severity of disease classification score, IP and TR.

METHODS

This study took place in a 27-bed intensive care unit (ICU) of an Australian tertiary hospital. IP and TR outcomes were measured at the sacrum and greater trochanter. Repeated measures analyses of variance (ANOVAs) and doubly multivariate repeated measures ANOVAs were conducted using peak pressure index (PPI), peak time (PT), settled time constant (STC) and normalised hyperaemic area (NHA) measures of TR as outcomes. Participant type, body mass index (BMI), Braden and APACHE II scores and patient body temperature were considered as between-groups factors and covariates.

RESULTS

We recruited 23 low- and high-acuity ICU patients and nine healthy adult volunteers. Not all IP readings could be obtained from ICU patients. TR readings were collected from all recruited patients, but not all TR measurements were mutually uncorrelated. Controlling for age, PPI readings differed between participant types (p=0.093), with the highest values associated with high-acuity patients and the lowest with healthy adults; the association was not substantive when controlling for age and BMI. Age was a significant variable (p=0.008), with older participants having higher scores than younger ones. No statistically significant associations between any measured parameter and TR variables were observed. However, temperature was revealed to be related to TR (p=0.091).

CONCLUSIONS

Although not powered to detect significant effects, this pilot analysis has determined several associations of importance, with differences in outcomes observed between low- and high-acuity ICU patients; and between ICU patients and healthy volunteers.

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.

Bioengineering considerations in the prevention of medical device-related pressure ulcers

BACKGROUND

In recent years, it has become increasingly apparent that medical device-related pressure ulcers represent a significant burden to both patients and healthcare providers. Medical devices can cause damage in a variety of patients from neonates to community based adults. To date, devices have typically incorporated generic designs with stiff polymer materials, which impinge on vulnerable soft tissues. As a result, medical devices that interact with the skin and underlying soft tissues can cause significant deformations due to high interface pressures caused by strapping or body weight.

METHODS

This review provides a detailed analysis of the latest bioengineering tools to assess device related skin and soft tissue damage and future perspectives on the prevention of these chronic wounds. This includes measurement at the device-skin interface, imaging deformed tissues, and the early detection of damage through biochemical and biophysical marker detection. In addition, we assess the potential of computational modelling to provide a means for device design optimisation and material selection.

INTERPRETATION

Future collaboration between academics, industrialists and clinicians should provide the basis to improve medical device design and prevent the formation of these potentially life altering wounds. Ensuring clinicians report devices that cause pressure ulcers to regulatory agencies will provide the opportunity to identify and improve devices, which are not fit for purpose.

Prevalence of pressure injury among Chinese community-dwelling older people and its risk factors: A national survey based on Chinese Longitudinal Healthy Longevity Survey

AIM

To investigate the distribution of pressure injuries among older adults in China and to identify the associated risk factors.

DESIGN

Cross-sectional study.

METHODS

The identified subjects were collected from 2012 wave of a national Chinese Longitudinal Healthy Longevity Survey. Older people were defined as being 65 years of age or older. We used chi-square test and binary logistic regression to investigate the risk factors of pressure injury development.

RESULTS

A total of 55 older people were documented as suffering from pressure injuries among 6,961 older Chinese adults, with a prevalence of 0.8%. In the group of disability, the prevalence of pressure injuries from high to low was 3.6% in the highly limited group, 0.4% in the moderately limited group, and 0.3% in the not limited group. The prevalence of pressure injury among older people with stroke, cancer, and dementia were 2%, 4.2%, and 6.6%, respectively. According to the final binary logistic regression analysis, age, disability, incontinence, cancer, and dementia emerged as important risk factors for pressure injury development.

CONCLUSION

Pressure injury among Chinese community-dwelling aged people was shown to be associated with age, disability, incontinence, cancer, and dementia. As the development of pressure injury may distinctly increase the burden on individuals and healthcare systems, the social and related institutions should actively prevent and control the disease.

IMPACT

The results of this study will improve the identification of pressure injury among older Chinese people and contribute to the development of effective pressure injury risk management interventions.

In-Depth Investigation into the Transient Humidity Response at the Body-Seat Interface on Initial Contact Using a Dual Temperature and Humidity Sensor

Relative humidity (RH) at the body-seat interface is considered an important factor in both sitting comfort and generation of health concerns such as skin lesions. Technical difficulties appear to have limited research aimed at the detailed and simultaneous exploration of RH and temperature changes at the body-seat interface; using RH sensors without the capability to record temperature where RH is recorded. To explore the causes of a spike in RH consistently produced on first contact between body and seat surface, we report data from the first use of dual temperature and RH (HTU21D) sensors in this interface. Following evaluation of sensor performance, the effect of local thermal changes on RH was investigated. The expected strong negative correlation between temperature and RH (R² = −0.94) supported the importance of considering both parameters when studying impact of sitting on skin health. The influence of sensor movement speed (higher velocity approach: 0.32 cm/s ± 0.01 cm/s; lower velocity approach: 0.17 cm/s ± 0.01 cm/s) into a static RH region associated with a higher local temperature were compared with data gathered by altering the rate of a person sitting. In all cases, the faster sitting down (or equivalent) generated larger RH outcomes: e.g., in human sitting 53.7% ± 3.3% RH (left mid-thigh), 56.4% ± 5.1% RH (right mid-thigh) and 53.2% ± 2.7% RH (Coccyx). Differences in size of RH change were seen across the measurement locations used to study the body-seat interface. The initial sitting contact induces a transient RH response (duration ≤ 40 s) that does not accurately reflect the microenvironment at the body-seat interface. It is likely that any movement during sitting would result in similar artefact formation. As a result, caution should be taken when investigating RH performance at any enclosed interface when the surfaces may have different temperatures and movement may occur.

Effects of humidity on skin friction against medical textiles as related to prevention of pressure injuries

Sustained pressure, shear forces, and friction, as well as elevated humidity/moisture, are decisive physical factors in the development of pressure injuries (PIs). To date, further research is needed in order to understand the influence of humidity and moisture on the coefficient of friction (COF) of skin against different types of medical textiles. The aim of this work was to investigate the effects of moisture caused by sweat, urine, or saline on the resulting COF of skin against different textiles used in the medical setting in the context of PI prevention. For that purpose, we performed physical measurements of static COFs of porcine skin followed by finite element (FE) computational modelling in order to illustrate the effect of increased COF at the skin on the resulting strains and stresses deep within the soft tissues of the buttocks. The COF of dry skin obtained for the 3 textiles varied between 0.59 (adult diaper) and 0.91 (polyurethane dressing). In addition, the COF increased with the added moisture in all of the tested cases. The results of the FE simulations further showed that increased COF results in elevated strain energy density and shear strain values in the skin and deeper tissues and, hence, in an increased risk for PI development. We conclude that moisture may accelerate PI formation by increasing the COF between the skin and the medical textile, regardless of the type of the liquid that is present. Hence, reduction of the wetness/moisture between the skin and fabrics in patients at a high risk of developing PIs is a key measure in PI prevention.

Microclimate: A critical review in the context of pressure ulcer prevention

Pressure ulcers are caused by sustained mechanical loading and deformation of the skin and subcutaneous layers between internal stiff anatomical structures and external surfaces or devices. In addition, the skin microclimate (temperature, humidity and airflow next to the skin surface) is an indirect pressure ulcer risk factor. Temperature and humidity affect the structure and function of the skin increasing or lowering possible damage thresholds for the skin and underlying soft tissues. From a pressure ulcer prevention research perspective, the effects of humidity and temperature next to the skin surface are inextricably linked to concurrent soft tissue deformation. Direct clinical evidence supporting the association between microclimate and pressure ulceration is sparse and of high risk of bias. Currently, it is recommended to keep the skin dry and cool and/or to allow recovery periods between phases of occlusion. The stratum corneum must be prevented from becoming overhydrated or from drying out but exact ranges of an acceptable microclimate are unknown. Therefore, vague terms like 'microclimate management' should be avoided but product and microclimate characteristics should be explicitly stated to allow an informed decision making. Pressure ulcer prevention interventions like repositioning, the use of special support surfaces, cushions, and prophylactic dressings are effective only if they reduce sustained deformations in soft tissues. This mode of action outweighs possible undesirable microclimate properties. As long as uncertainty exists efforts must be taken to use as less occlusive materials as possible. There seems to be individual intrinsic characteristics making patients more vulnerable to microclimate effects.

Effect of Humidified Noninvasive Ventilation on the Development of Facial Skin Breakdown

BACKGROUND

The use of noninvasive ventilation masks is known to cause damage to facial skin tissue, which affects both the efficacy of the intervention and the patient's quality of life. The use of humidification with noninvasive ventilation is a common practice, but its relative role in the development of facial pressure ulcers has not been fully studied.

METHODS

A crossover cohort design was used in this study, with 15 healthy volunteers. Each volunteer randomly received both 10 cm H2O of CPAP with and without humidification through an oronasal mask. Skin integrity was evaluated by measuring transepidermal water loss, skin hydration, and skin pH at the bridge of the nose. Device-skin interface conditions (pressure and microclimate) were recorded at the bridge of the nose and both cheeks. The pro-inflammatory cytokine interleukin-1α was collected from the nose bridge before and after CPAP application by using a skin analysis tape. Nasal symptoms were collected by using a validated 6-point score.

RESULTS

Humidified CPAP significantly increased transepidermal water loss (P < .001) and skin humidity (P = .02) compared with non-humidified CPAP. There were no significant differences in skin hydration, skin pH, skin temperature, and cytokine expression between both conditions. However, there was a trend of increased median ratios of interleukin-1α concentrations in the humidified CPAP. There was a significant increase in the interface pressure at the bridge of the nose after CPAP application (P = .02), with higher interface pressure values at the nose bridge compared with both left (P = .002) and right (P = .003) cheeks. The participants reported elevated nasal discomfort during non-humidified CPAP.

CONCLUSIONS

These findings indicated that noninvasive ventilation with humidification had a potential disrupting effect on the barrier function of facial skin, associated with changes in skin microclimate and function. Further research is required to establish the cause of mask-related skin damage and to evaluate the effects of mask design, application techniques, and air flow and humidity settings.

Development and evaluation of a new methodology for the fast generation of patient-specific Finite Element models of the buttock for sitting-acquired deep tissue injury prevention

The occurrence and management of Pressure Ulcers remain a major issue for patients with reduced mobility and neurosensory loss despite significant improvement in the prevention methods. These injuries are caused by biological cascades leading from a given mechanical loading state in tissues to irreversible tissue damage. Estimating the internal mechanical conditions within loaded soft tissues has the potential of improving the management and prevention of PU. Several Finite Element models of the buttock have therefore been proposed based on either MRI or CT-Scan data. However, because of the limited availability of MRI or CT-Scan systems and of the long segmentation time, all studies in the literature include the data of only one individual. Yet the inter-individual variability can't be overlooked when dealing with patient specific estimation of internal tissue loading. As an alternative, this contribution focuses on the combined use of low-dose biplanar X-ray images, B-mode ultrasound images and optical scanner acquisitions in a non-weight-bearing sitting posture for the fast generation of patient-specific FE models of the buttock. Model calibration was performed based on Ischial Tuberosity sagging. Model evaluation was performed by comparing the simulated contact pressure with experimental observations on a population of 6 healthy subjects. Analysis of the models confirmed the high inter-individual variability of soft tissue response (maximum Green Lagrange shear strains of 213 ± 101% in the muscle). This methodology opens the way for investigating inter-individual factors influencing the soft tissue response during sitting and for providing tools to assess PU risk.

Microclimate evaluation of strap-based wheelchair seating systems for persons with spinal cord injury: A pilot study

STUDY PURPOSE

The purpose of this pilot study was to assess microclimate characteristics of two versions of a strap-based wheelchair seating system (perforated and solid straps) and to conduct preliminary microclimate comparisons of subjects' current wheelchair seating systems.

MATERIALS AND METHODS

In this pilot study, the microclimate properties of two variations (solid and perforated) of a strap-based seating system were compared with two commonly used seating systems. Six subjects sat on three different seating systems each for 100-min test periods, while temperature and relative humidity were measured with a single sensor adjacent to the skin-seat interface. Additionally, thermal images of the seat interface were collected before and after each test period.

RESULTS

The thermal images revealed that the maximum surface temperature of the solid-strap-based seating system was significantly lower than the other seating systems, -1.21 °C. (95% CI -2.11 to -0.30, p = 0.02), immediately following transfer out of the seat. Five minutes after transferring out of the seat, the perforated-strap seat was significantly cooler than the other seats -0.94 °C. (95% CI -1.59 to -0.30), p = 0.01, as was the solid-strap-based seat, -1.66 °C. (95% CI -2.69 to -0.63), p = 0.01. There were no significant differences in interface temperature or relative humidity measured with the single sensor near the skin-seat interface.

CONCLUSION

This pilot study offers preliminary evidence regarding the microclimate of the strap-based seating systems compared with other common seating systems. Clinically, the strap-based seating system may offer another option for those who struggle with microclimate management.