Deep Tissue Injury: How Deep is Our Understanding?

Genomic Biomarkers Can Provide a Deeper Understanding of Recurrent Pressure Injuries

OBJECTIVE

To identify genetic biomarkers predisposing individuals with spinal cord injury (SCI) to recurrent pressure injuries (PIs).

METHODS

Repeated measures of the transcriptome profile of veterans with SCI at three Veterans Spinal Cord Injuries and Disorders Centers. Exclusion criteria included having significant active systemic disease at time of enrollment. Researchers obtained comprehensive profiles of clinical and health factors and demographic information relevant to PI history at enrollment and at each follow-up visit by reviewing patients' medical charts. Whole blood samples were collected at 6- to 12-month intervals for 2 to 4 years. In addition to DNA profiling with whole genome sequencing of the patients, RNA sequencing was performed to assess pathways associated with PI risk.

RESULTS

Whole genome sequencing analysis identified 260 genes that showed increased prevalence of single-nucleotide variations in exonic regions with high (>20) combined annotation-dependent depletion scores between persons with high versus low intramuscular adipose tissue levels when cross-referenced with persons who had recurrent PIs. Gene set enrichment analysis using Hallmark and KEGG (Kyoto Encyclopedia of Genes and Genomes) gene sets of these candidate genes revealed enrichment in genes encoding proteins involved in fatty acid metabolism (P < .01). Further, RNA sequencing revealed upregulated activity in biological senescence pathways and downregulated activity in antimicrobial protection pathways.

CONCLUSIONS

Genomic biomarkers may complement electronic health records to support management of complex interactive health issues such as risk of recurrent PIs in people with SCI. These findings may also be leveraged for homogeneous phenotypic grouping of higher-risk individuals.

A pressure monitoring approach for pressure ulcer prevention

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Quantification of Comfort for the Development of Binding Parts in a Standing Rehabilitation Robot

Human-machine interfaces (HMI) refer to the physical interaction between a user and rehabilitation robots. A persisting excessive load leads to soft tissue damage, such as pressure ulcers. Therefore, it is necessary to define a comfortable binding part for a rehabilitation robot with the subject in a standing posture. The purpose of this study was to quantify the comfort at the binding parts of the standing rehabilitation robot. In Experiment 1, cuff pressures of 10-40 kPa were applied to the thigh, shank, and knee of standing subjects, and the interface pressure and pain scale were obtained. In Experiment 2, cuff pressures of 10-20 kPa were applied to the thigh, and the tissue oxygen saturation and the skin temperature were measured. Questionnaire responses regarding comfort during compression were obtained from the subjects using the visual analog scale and the Likert scale. The greatest pain was perceived in the thigh. The musculoskeletal configuration affected the pressure distribution. The interface pressure distribution by the binding part showed higher pressure at the intermuscular septum. Tissue oxygen saturation (StO₂) increased to 111.9 ± 6.7% when a cuff pressure of 10 kPa was applied and decreased to 92.2 ± 16.9% for a cuff pressure of 20 kPa. A skin temperature variation greater than 0.2 °C occurred in the compressed leg. These findings would help evaluate and improve the comfort of rehabilitation robots.

Detectability of low-oxygenated regions in human muscle tissue using near-infrared spectroscopy and phantom models

The present work aims to describe the detectability limits of hypoxic regions in human muscle under moderate thicknesses of adipose tissue to serve as a groundwork for the development of a wearable device to prevent pressure injuries. The optimal source-detector distances, detection limits, and the spatial resolution of hypoxic volumes in the human muscle are calculated using finite element method-based computer simulations conducted on 3-layer tissue models. Silicone phantoms matching the simulation geometries were manufactured, and their measurement results were compared to the simulations. The simulations showed good agreement with the performed experiments. Our results show detectability of hypoxic volumes under adipose tissue thicknesses of up to 1.5 cm. The maximum tissue depth, at which hypoxic volumes could be detected was 2.8 cm. The smallest detectable hypoxic volume in our study was 1.2 cm³. We thus show the detectability of hypoxic volumes in sizes consistent with those of early-stage pressure injury formation and, consequently, the feasibility of a device to prevent pressure injuries.

The Impact of Limited Prosthetic Socket Documentation: A Researcher Perspective

The majority of limb prostheses are socket mounted. For these devices, the socket is essential for adequate prosthetic suspension, comfort, and control. The socket is unique among prosthetic components as it is not usually mass-produced and must instead be custom-made for individual residual limbs by a prosthetist. The knowledge of what constitutes "good" socket fit is gained by expert prosthetists and technicians over years of experience, and rarely documented. The reliance on tacit knowledge makes it difficult to standardize the criteria for a well-fitting socket, leading to difficulties understanding the impact of socket fit. Despite its importance, the workflow for socket fitting is often overlooked in literature. Due to the customized nature of sockets, if information is provided in literature, generally only the type of socket and suspension mechanism is noted, with information regarding the fitting and manufacturing processes omitted. In this article, the concerns, issues and consequences arising from lack of upper and lower limb socket documentation are discussed from a researcher perspective, supported by healthcare professionals and socket fabrication specialists. Key changes are proposed to the way socket manufacturing and evaluation are documented to assist future research.

Early Identification of Deep-Tissue Pressure Injury Using Long-Wave Infrared Thermography: A Blinded Prospective Cohort Study

BACKGROUND

The current clinical standard for diagnosing deep-tissue pressure injury (DTPI) is visual inspection. This method is subjective and only presents to the observer the external "picture;" deeper tissues are disguised from the observer. In contrast, long-wave infrared thermography (LWIT) can capture an image of the area of concern and detect tissue temperature relative to the level of tissue perfusion.

OBJECTIVE

To determine the efficacy of a handheld LWIT device and software solution as an adjunct to the current clinical standard of visual skin assessment to detect nonvisual pathophysiologic changes of DTPI.

METHODS

Investigators performed a blinded, prospective cohort study scanning participants' sacral area and bilateral heels with the LWIT device. Follow-up imaging took place throughout patient stays (on admission and 3, 7, 14, and 25 days thereafter). Clinicians were blinded to the LWIT images, and all participants received standard care for the prevention and treatment of wounds.

RESULTS

Among the 70 participants enrolled in this study, there were 131 anatomical areas with intact skin at the time of admission. Four areas with initially intact skin progressed to visually identifiable DTPI. On all four of these areas, the LWIT device identified a previsual temperature anomaly before there existed a visually identifiable DTPI.

CONCLUSIONS

The outcomes of this study suggest objective and quantitative documentation of temperature change using the LWIT device can serve as an indication of DTPI formation before visual identification is possible. Accordingly, it may allow for earlier detection of DTPI, decreasing the risk of associated complications to the patient and allowing for earlier, targeted intervention.

Modelling, design and control of a new seat-cushion for pressure ulcers prevention

Pressure ulcers are a frequent complication in patients having limited activity and mobility (e.g., elderly people, spinal cord injury patients, people with disabilities, etc.). The aim of this work is the conceptual design, modelling and control of a new seat cushion for pressure ulcers prevention. The whole system (constituted by the seat cushion equipped with a real-time pressure mapping with closed-loop control) is designed to identify the critical points on the human skin, before pressure ulcers creation, and to be able to distribute the contact pressure between the human and cushion avoiding wound creation. The seat cushion is constituted by soft air-cells actuated by air flow. To define the shape and size of the soft air-cells, finite element simulations are carried out, analysing the internal volume reduction with external loads application to reproduce the variable stiffness. The data obtained by finite element analysis are used to simulate inflation and deflation of the soft bubble air-cells. Finally, the control systems of a single air-cell and of the whole cushion are designed and simulated. The novelty of our work consists in the conception of a seat cushion able to recognise higher and lower risk zones of pressure ulcer generation on the human skin and to provide compensation automatically. This work can therefore be considered in line with the sustainable development goals recently launched by the EU Commission.

A Visual Feedback Tool for Quantitative Pressure Monitoring in Lower-Limb Prosthetic Sockets

Obtaining a good socket fit is an iterative process dependent on the skill and experience of the prosthetist creating it and requires individualisation based on the size and shape. There is no standard measurement system used to aid prosthetic socket creation despite the severe impacts on physical health and quality of life if one is ill fitting. Pressure sensors embedded in a prosthetic socket were used to collect data at the socket–residuum interface. To choose an interpolation method, the sensor array was simplified to a 2D grid with a border for extrapolation and tested using previously collected walking test pressure data. Four multivariable interpolation methods were evaluated to create a colour map of the pressure data. Radial basis function interpolation was chosen, as it produced a clear image with a graduated interpolation between data points, and was used to create a colour map across the surface of a 3D prosthetic socket model. For the model to be accessible to clinical audiences, a desktop application was created using PyQt to view the model. The application allowed for connection to the sensors via Bluetooth, with the pressure data updating on the 3D model in real time. Clinician feedback on the application showed the potential for a clinical product; however, further development informed by feedback from rehabilitation clinicians and prosthesis users is required.

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

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

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.

Flexible thread-based electrochemical sensors for oxygen monitoring

Oxygen plays a key role in human physiology and is abnormally modulated in various disease pathologies making its in situ monitoring quite important. Most oxygen sensors are not able to measure oxygen levels deep inside the tissue or have mismatched electrode-tissue interfaces. In this study we developed a flexible thread-based oxygen sensor that combines the unique advantages of minimal invasiveness and superior flexibility offering the possibility for tissue integration. The sensor is featured by a simple and low-cost fabrication approach which allows for measuring the overall oxygen concentration either over a large surface area or locally at any spot in any three-dimensional environment with high spatial accuracy and high sensitivity. The sensor can sensitively detect dissolved oxygen levels within the physiological range of tissue oxygenation. The sensor's performance is insensitive to pH variation from 5.8 to 8.0. The sensor shows good repeatability and stability over a period of one week in phosphate buffered saline. In addition, the signal variation is less than 10% after hundreds of cycles of physical bending. Using a hydrogel-based tissue model the sensor has been shown to probe dissolved oxygen levels at different spatial locations inside a tissue-like environment.

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

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

Comparing the Braden and Jackson/Cubbin Pressure Injury Risk Scales in Trauma-Surgery ICU Patients

BACKGROUND

The occurrence of pressure injury in the critical care environment has multiple risk factors. Prevention requires reliable assessment tools to help predict injury risk. The Braden scale, a commonly used risk assessment tool, has been shown to have poor predictive properties in critical care patients. The Jackson/Cubbin scale was developed specifically for pressure injury risk stratification in critically ill patients and has demonstrated acceptable predictive properties in the general critical care population but has not been examined in critically ill trauma-surgical patients.

OBJECTIVE

To compare the predictive properties of the Braden and Jackson/Cubbin scales in a trauma-surgical critical care population.

METHODS

A retrospective medical records review was performed to evaluate the clinical characteristics of 366 trauma-surgical critical care patients. Additionally, the negative predictive value, positive predictive value, sensitivity, specificity, and receiver operating characteristic curve with area under the curve of the Braden and Jackson/Cubbin scales were determined.

RESULTS

The sample consisted of primarily middle-aged (mean [SD], 56 [19] years) men (64%) admitted after trauma (71%). The participants who developed pressure injuries were older, more often required vasopressors and mechanical ventilation, and were less mobile. Predictive properties for the Braden and Jackson/Cubbin scales, respectively, were as follows: negative predictive value, 78% versus 87%; positive predictive value, 53% versus 66%; sensitivity, 17% versus 54%; specificity, 95% versus 92%; and area under the curve, 0.710 versus 0.793.

CONCLUSION

The Jackson/Cubbin scale demonstrated superior predictive properties and discrimination compared with the Braden scale for pressure injury risk prediction in critically ill trauma-surgical patients.

Ultrasound assessment of deep tissue on the wound bed and periwound skin: A classification system using ultrasound images

AIMS

Given the utility of ultrasonography in assessing pressure injury, some ultrasonographic findings have already been used as indicators of deep tissue pressure injury. Despite reports showing that a cloud-like ultrasonographic pattern reflected the presence of deep tissue necrosis, identifying cloud-like patterns was difficult given the presence of similar findings, such as a cobblestone-like pattern. This case series reports patients with pressure injuries who presented with a cloud-like (five cases) and cobblestone-like (four cases) pattern during ultrasonography.

METHODS

This study was conducted at a Japanese university hospital. Participants included patients who underwent routine examination by an interdisciplinary pressure injury team. Pressure injury severity was assessed using the DESIGN-R® scoring system and the wound size were measured using ImageJ software based on the wound photograph.

RESULTS

Among the five cases showing a cloud-like pattern upon ultrasonography, all exhibited an increase in the total DESIGN-R® score, while three exhibited an increase in wound size. On the other hand, all four cases showing a cobblestone-like pattern displayed no increase in the total DESIGN-R® score and a decrease in wound size.

CONCLUSION

This study suggested that distinguishing between cloud-like and cobblestone-like ultrasonography patterns is necessary for determining the presence or absence of deep tissue pressure injury. In order to comprehensively assess pressure injuries with ultrasonography, future studies should be conducted in a large number of participants.

Circumferential tissue compression at the lower limb during walking, and its effect on discomfort, pain and tissue oxygenation: Application to soft exoskeleton design

Soft exoskeletons apply compressive forces at the limbs via connection cuffs to actuate movement or stabilise joints. To avoid excessive mechanical loading, the interface with the wearer's body needs to be carefully designed. The purpose of this study was to establish the magnitude of circumferential compression at the lower limb during walking that causes discomfort/pain. It was hypothesized that the thresholds differ from those during standing. A cohort of 21 healthy participants were tested using two sizes of pneumatic cuffs, inflated at the thigh and calf in a tonic or phasic manner. The results showed lower inflation pressures triggering discomfort/pain at the thigh, with tonic compression, and wider pneumatic cuffs. The thresholds were lower during walking than standing still. Deep tissue oxygenation increased during phasic compression and decreased during tonic compression. According to the findings, circumferential compression by soft exoskeletons is preferably applied at anatomical sites with smaller volumes of soft tissue, using narrow connection cuffs and inflation pressures below 14 kPa.

The effect of simulated circumferential soft exoskeleton compression at the knee on discomfort and pain

There is a lack of data and guidance on soft exoskeleton pressure contact with the body. The purpose of this research was to study the relationship between circumferential loading at the knee and discomfort/pain, to inform the design of soft exoskeletons/exosuits. The development of discomfort and pain was studied during standing and walking with circumferential compression using a pneumatic cuff. Our results show higher tolerance for intermittent than continuous compression during standing. Discomfort was triggered at pressures ranging from 13.7 kPa (continuous compression) to 30.4 kPa (intermittent compression), and pain at 52.9 kPa (continuous compression) to 60.6 kPa (intermittent compression). During walking, cyclic compression caused an increase in discomfort with time. Higher cuff inflation pressures caused an earlier onset and higher end intensities of discomfort than lower pressures. Cyclic cuff inflation of 10 kPa and 20 kPa was reasonably well tolerated. Practitioner summary Soft exoskeleton compression of the knee was simulated during static and dynamic compression cycles. The results can be used to understand how users tolerate pressure at the knee, and also to understand the levels at which discomfort and pain are experienced. Abbreviations: BMI: body mass index; DDT: discomfort detection threshold; EndVAS: end of experiment rating on visual analog discomfort scale; PDT: pain detection threshold; SD: standard deviation; SE: standard error; TSP: temporal summation of pain; VAS: visual analogue scale.

Discomfort/Pain and Tissue Oxygenation at the Lower Limb During Circumferential Compression: Application to Soft Exoskeleton Design

OBJECTIVE

To establish the relationship between circumferential compression on the lower limb during simulated ramp and staircase profile loading, and the resultant relationship with discomfort/pain and tissue oxygenation.

BACKGROUND

Excessive mechanical loading by exoskeletons on the body can lead to pressure-related soft tissue injury. Potential tissue damage is associated with objective oxygen deprivation and accompanied by subjective perception of pain and discomfort.

METHOD

Three widths of pneumatic cuffs were inflated at the dominant thigh and calf of healthy participants using two inflation patterns (ramp and staircase), using a computer-controlled pneumatic rig. Participants rated discomfort on an electronic visual analog scale and deep tissue oxygenation was monitored using near infrared spectroscopy.

RESULTS

Circumferential compression with pneumatic cuffs triggered discomfort and pain at lower pressures at the thigh, with wider cuffs, and with a ramp inflation pattern. Staircase profile compression caused an increase in deep tissue oxygenation, whereas the ramp profile compression decreased it.

CONCLUSION

Discomfort and pain during circumferential compression at the lower limb is related to the width of pneumatic cuffs, the inflation pattern, and the volume of soft tissue at the assessment site. The occurrence of pain is also possibly related to the decrease in deep tissue oxygenation during compression.

APPLICATION

Our findings can be used to inform safe and comfortable design of soft exoskeletons to avoid discomfort and possible soft tissue injury.

How patient migration in bed affects the sacral soft tissue loading and thereby the risk for a hospital-acquired pressure injury

Head‐of‐bed (HOB) elevation is a common clinical practice in hospitals causing the patient's body to slide down in bed because of gravity. This migration effect likely results in tissue shearing between the sacrum and the support surface, which increases the risk for pressure injuries. StayInPlace (HillRom Inc.) is a commercial migration‐reduction technology (MRT) incorporated in intensive care bedframes. Yet, the effects of migration‐reduction on tissue shear stresses during HOB elevation are unknown. We analysed relationships between migration and resulting sacral soft tissue stresses by combining motion analysis and three‐dimensional finite element modelling of the buttocks. Migration data were collected for 10 subjects, lying supine on two bedframe types with and without MRT, and at HOB elevations of 45°/65°. Migration data were used as displacement boundary conditions for the modelling to calculate tissue stress exposures. Migration values for the conventional bed were 1.75‐ and 1.6‐times greater than those for the migration‐reduction bed, for elevations of 45° and 65°, respectively (P < .001). The modelling showed that the farther the migration, the greater the tissue stress exposures. Internal stresses were 1.8‐fold greater than respective skin stresses. Our results, based on the novel integrated experimental‐computational method, point to clear biomechanical benefits in minimising migration using MRT.

Seated buttocks anatomy and its impact on biomechanical risk

AIM

The objective of this study was to describe the amount, types, and shapes of tissue present in the buttocks during sitting (i.e., seated buttocks soft tissue anatomy), and the impact of seated buttocks soft tissue anatomy on biomechanical risk.

MATERIALS AND METHODS

The buttocks of 35 people, including 29 full-time wheelchair users with and without a history of pelvic pressure ulcers were scanned sitting upright on 3" of flat HR45 foam in a FONAR Upright MRI. Multi-planar scans were analyzed to calculate bulk tissue thickness, tissue composition, gluteus maximus coverage at the ischium, the contour of the skin, and pelvic tilt.

RESULTS

Bulk tissue thickness varied from 5.6 to 32.1 mm, was composed mostly of adipose tissue, and was greatest in the able-bodied cohort. Skin contours varied significantly across status group, with wheelchair users with a history of pressure ulcers having tissue with a peaked contour with a radius of curvature of 65.9 mm that wrapped more closely to the ischium (thickness at the apex = 8.2 mm) as compared to wheelchair users with no pressure ulcer history (radius of curvature = 91.5 mm and apex thickness = 14.5 mm). Finally, the majority of participants presented with little to no gluteus coverage over their ischial tuberosity, regardless of status group.

CONCLUSIONS

This study provides quantitative evidence that Biomechanical Risk, or the intrinsic characteristic of an individual's soft tissues to deform in response to extrinsic applied forces, is greater in individuals at greater risk for pressure ulcers.

Influence of clamping parameters on the trauma of rabbit small intestine tissue

BACKGROUND

During clamping operation for minimally invasive intestinal surgery, patients often suffer from small intestine trauma. This phenomenon will lead to various complications, increase recovery time and cause pain for patients.

METHODS

In this paper, preliminary simulations of small intestine clamping operations in the minimally invasive surgery were made by conducting compression tests under different clamping stresses, durations and loading rates. A pathological grading system was designed after microscope observation to quantitatively evaluate the trauma of small intestine tissue.

FINDINGS

Results showed that different traumas: inflammatory cell infiltration, hyperemia, hemorrhage and rupture between serosa and muscularis, as well as villi destruction could be observed on the clamping sites of the small intestine tissue. When the clamping parameters (clamping stress, duration and loading rate) increased, the degree of the tissue trauma increased. There existed safe thresholds for clamping operations, at which severe trauma of small intestine tissues could be avoided in the clamping process.

INTERPRETATION

As the clamping parameters increased, the strain, that is the deformation of the small intestine tissue increased. The increase in the deformation would induce the aggravation of trauma degree.

A Systematic Review and Meta-Analysis of the Pressure-Induced Vasodilation Phenomenon and Its Role in the Pathophysiology of Ulcers

BACKGROUND

Physiologic studies show that tissue perfusion increases during moderate amounts of tissue compression. This is attributed to sensory nerves initiating a vasodilatory cascade referred to as pressure-induced vasodilation.

METHODS

PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched for studies investigating perfusion during pressure exposure longer than 10 minutes. Retrieved studies were assessed using the Office of Health Assessment and Translation Risk of Bias Rating Tool for Human and Animal Studies. Results were pooled with random effects models. The body of evidence was rated using the Office of Health Assessment and Translation approach.

RESULTS

Twenty-nine articles were included, of which 19 articles were included in meta-analyses. The evidence indicates that moderate amounts of tissue compression have the capacity to increase perfusion in healthy humans by 46 percent (95 percent CI, 30 to 62 percent). Using the Office of Health Assessment and Translation approach, the authors found a high level of confidence in the body of evidence. Pressure-induced vasodilation blockade was associated with increased pressure ulcer formation. Pressure-induced vasodilation was impaired by neuropathy and by the drugs diclofenac and amiloride.

CONCLUSIONS

This systematic review and meta-analysis indicates that healthy humans have the capacity to increase local perfusion in response to mechanical stress resulting from tissue compression. Because pressure-induced vasodilation is mediated by sensory nerves, pressure-induced vasodilation emphasizes the importance of sensory innervation for durable tissue integrity. Pressure-induced vasodilation impairment seems to provide a complementary explanation for the susceptibility of neuropathic tissues to pressure-induced lesions.

Magnetic resonance elastography of skeletal muscle deep tissue injury

The current state-of-the-art diagnosis method for deep tissue injury in muscle, a subcategory of pressure ulcers, is palpation. It is recognized that deep tissue injury is frequently preceded by altered biomechanical properties. A quantitative understanding of the changes in biomechanical properties preceding and during deep tissue injury development is therefore highly desired. In this paper we quantified the spatial-temporal changes in mechanical properties upon damage development and recovery in a rat model of deep tissue injury. Deep tissue injury was induced in nine rats by two hours of sustained deformation of the tibialis anterior muscle. Magnetic resonance elastography (MRE), T₂ -weighted, and T₂ -mapping measurements were performed before, directly after indentation, and at several timepoints during a 14-day follow-up. The results revealed a local hotspot of elevated shear modulus (from 3.30 ± 0.14 kPa before to 4.22 ± 0.90 kPa after) near the center of deformation at Day 0, whereas the T₂ was elevated in a larger area. During recovery there was a clear difference in the time course of the shear modulus and T₂ . Whereas T₂ showed a gradual normalization towards baseline, the shear modulus dropped below baseline from Day 3 up to Day 10 (from 3.29 ± 0.07 kPa before to 2.68 ± 0.23 kPa at Day 10, P < 0.001), followed by a normalization at Day 14. In conclusion, we found an initial increase in shear modulus directly after two hours of damage-inducing deformation, which was followed by decreased shear modulus from Day 3 up to Day 10, and subsequent normalization. The lower shear modulus originates from the moderate to severe degeneration of the muscle. MRE stiffness values were affected in a smaller area as compared with T₂ . Since T₂ elevation is related to edema, distributing along the muscle fibers proximally and distally from the injury, we suggest that MRE is more specific than T₂ for localization of the actual damaged area.

Two-Hourly Repositioning for Prevention of Pressure Ulcers in the Elderly: Patient Safety or Elder Abuse?

For decades, aged care facility residents at risk of pressure ulcers (PUs) have been repositioned at two-hour intervals, twenty-four-hours-a-day, seven-days-a-week (24/7). Yet, PUs still develop. We used a cross-sectional survey of eighty randomly selected medical records of residents aged ≥ 65 years from eight Australian Residential Aged Care Facilities (RACFs) to determine the number of residents at risk of PUs, the use of two-hourly repositioning, and the presence of PUs in the last week of life. Despite 91 per cent (73/80) of residents identified as being at risk of PUs and repositioned two-hourly 24/7, 34 per cent (25/73) died with one or more PUs. Behaviours of concern were noted in 72 per cent (58/80) of residents of whom 38 per cent (22/58) were restrained. Dementia was diagnosed in 70 per cent (56/80) of residents. The prevalence of behaviours of concern displayed by residents with dementia was significantly greater than by residents without dementia (82 per cent v 50 per cent, p = 0.028). The rate of restraining residents with dementia was similar to the rate in residents without dementia. Two-hourly repositioning failed to prevent PUs in a third of at-risk residents and may breach the rights of all residents who were repositioned two-hourly. Repositioning and restraining may be unlawful. Rather than only repositioning residents two-hourly, we recommend every resident be provided with an alternating pressure air mattress.

Pressure Injury Risk Factors in Critical Care Patients: A Descriptive Analysis

BACKGROUND

Pressure injury (PI) development in the critical care population is multifactorial. Despite the application of evidence-based prevention strategies, PIs do occur and may be unavoidable in some patients.

OBJECTIVES

To describe the risk factors associated with PI development in a sample of medical-surgical intensive care unit patients and determine whether these risk factors were congruent with the risk factors proposed in the work of the National Pressure Ulcer Advisory Panel on unavoidable PIs.

METHODS

A retrospective, descriptive design was used to determine the PI risk factors present in a sample of 57 critically ill patients admitted to the medical-surgical intensive care unit for more than 24 hours and who acquired a PI during their admission.

RESULTS

The most frequently identified risk factors were immobility (n = 57 [100%]), septic shock (n = 31 [54%]), vasopressor use (n = 37 [65%]), head-of-bed elevation greater than 30° (n = 53 [93%]), sedation (n = 50 [87.7%]), and mechanical ventilation for more than 72 hours (n = 46 [81%]). The most common PI location was the sacrum (n = 32 [56%]), and the most common stage reported was deep-tissue PI (n = 39 [68%]). The mean number of days to PI development was reported at 7.5 (SD, 7.2) days.

CONCLUSIONS

Results of this descriptive study were congruent with the literature surrounding the clinical situations that predispose patients to unavoidable PIs. While the implementation of aggressive PI prevention strategies is essential to reducing PI rates, it is important to recognize that in certain populations, such as the critically ill, exposure to certain risk factors may potentially escalate PI risk beyond the scope of prevention and result in an unavoidable PI. Recognizing these risk factors is significant in the journey to differentiate PIs that result from a lack of preventive care from those that may be prevention immune.

Biomechanical analysis of different dynamic sitting techniques: an exploratory study

Prolonged static sitting in wheelchairs increases the risk of pressure ulcers. This exploratory study proposed three dynamic sitting techniques in order to reduce the risk of developing pressure ulcer during wheelchair sitting, namely lumbar prominent dynamic sitting, femur upward dynamic sitting, and lumbar prominent with femur upward dynamic sitting. The purpose of this study was to analyze the biomechanical effects of these three techniques on interface pressure. 15 able-bodied people were recruited as subjects to compare the aforementioned sitting techniques in a random order. All parameters, including dynamic contact area, dynamic average pressure, and dynamic peak pressure on backrest and seat were measured and compared. In result, when compared with lumbar prominent dynamic sitting, femur upward dynamic sitting and lumbar prominent with femur upward dynamic sitting appeared to yield significantly lower dynamic average and peak pressure on the back part of seat, and significantly higher dynamic average and peak pressure on the front part of seat. This study can serve as a reference point for clinical physicians or wheelchair users to identify a suitable dynamic sitting technique.

An advanced magnetic resonance imaging perspective on the etiology of deep tissue injury

Early diagnosis of deep tissue injury remains problematic due to the complicated and multifactorial nature of damage induction and the many processes involved in damage development and recovery. In this paper, we present a comprehensive assessment of deep tissue injury development and remodeling in a rat model by multiparametric magnetic resonance imaging (MRI) and histopathology. The tibialis anterior muscle of rats was subjected to mechanical deformation for 2 h. Multiparametric in vivo MRI, consisting of T2, T2*, mean diffusivity (MD), and angiography measurements, was applied before, during, and directly after indentation as well as at several time points during a 14-day follow-up. MRI readouts were linked to histological analyses of the damaged tissue. The results showed dynamic change in various MRI parameters, reflecting the histopathological status of the tissue during damage induction and repair. Increased T2 corresponded with edema, muscle cell damage, and inflammation. T2* was related to tissue perfusion, hemorrhage, and inflammation. MD increase and decrease was reported on the tissue’s microstructural integrity and reflected muscle degeneration and edema as well as fibrosis. Angiography provided information on blockage of blood flow during deformation. Our results indicate that the effects of a single damage-causing event of only 2 h of deformation were present up to 14 days. The initial tissue response to deformation, as observed by MRI, starts at the edge of the indentation. The quantitative MRI readouts provided distinct and complementary information on the extent, temporal evolution, and microstructural basis of deep tissue injury-related muscle damage.

NEW & NOTEWORTHY We have applied a multiparametric MRI approach linked to histopathology to characterize damage development and remodeling in a rat model of deep tissue injury. Our approach provided several relevant insights in deep tissue injury. Response to damage, as observed by MRI, started at some distance from the deformation. Damage after a single indentation period persisted up to 14 days. The MRI parameters provided distinct and complementary information on the microstructural basis of the damage.

Blood flow responses over sacrum in nursing home residents during one hour bed rest

Objectives

To describe individual BF responses in a nursing home resident population for one‐hour periods of bed rest.

Methods

BF was measured for one hour over the sacrum in 0° supine position and 30° supine tilt position in 25 individuals aged 65 y or older while lying on a pressure‐redistributing mattress. Measurements were made at three tissue depths (1, 2, and 10 mm) using the noninvasive optical techniques, LDF and PPG.

Results

Eleven participants had a PIV response at 1 mm depth in both positions and seven participants had a lack of this response at this depth and positions. The BF response at 1 mm depth appeared immediately and remained over, or below, baseline for the entire 60 min of loading in both positions. These BF patterns were also seen in deeper tissue layers.

Conclusions

The cutaneous BF response among the nursing home residents was distinct, appeared early, and remained during the one hour of loading.

Computerized Cuff Pressure Algometry as Guidance for Circumferential Tissue Compression for Wearable Soft Robotic Applications: A Systematic Review

In this article, we review the literature on quantitative sensory testing of deep somatic pain by means of computerized cuff pressure algometry (CPA) in search of pressure-related safety guidelines for wearable soft exoskeleton and robotics design. Most pressure-related safety thresholds to date are based on interface pressures and skin perfusion, although clinical research suggests the deep somatic tissues to be the most sensitive to excessive loading. With CPA, pain is induced in deeper layers of soft tissue at the limbs. The results indicate that circumferential compression leads to discomfort at ∼16-34 kPa, becomes painful at ∼20-27 kPa, and can become unbearable even below 40 kPa.

Evaluation of the effect of different sitting assistive devices in reclining wheelchair on interface pressure

Background

Reclining wheelchair users often add one or more sitting assistive devices to their wheelchairs, but the effect of these additional sitting assistive devices on the risk of pressure ulcers has rarely been investigated. This study examined the four modes of reclining wheelchair without and with different sitting assistive devices, namely the back reclined mode, the lumbar support with back reclined mode, the femur upward with back reclined mode, and the lumbar support with femur upward with back reclined mode, in terms of their effects on human-wheelchair interface pressure.

Methods

This study recruited 16 healthy participants to undergo the aforementioned four modes in random order and have their human-wheelchair interface pressure measured. The initial setting of experimental reclining wheelchair backrest was pushed backward to reach a 150° recline. The data on interface pressure were collected for 5 s while the participant maintained a stable sitting position. The contact area, average pressure, and peak pressure on the back area, ischial area, and femur area were recorded and calculated.

Results

Among all tested modes, the lumbar support with femur upward with back reclined mode provided the most significant reduction in stress load on the ischial area (P ≤ 0.010) and shifted part of the load to the femur area (P ≤ 0.009).

Conclusions

This study quantified the effects of and differences between various reclining wheelchair–sitting assistive device combination modes. These findings are useful for the decision-making processes of rehabilitation physicians, wheelchair users, and manufacturers.

Beware of the toilet: The risk for a deep tissue injury during toilet sitting

A pressure injury (PrI) compromises quality of life and can be life-threatening. The fundamental cause of PrIs is sustained deformations in weight-bearing soft tissues, e.g., during prolonged sitting on inadequate surfaces such as a toilet seat. In nursing homes and geriatric facilities, patients need assistance using the restroom, and patients being left on the toilet for tens-of-minutes is a real-world scenario, unfortunately. Nevertheless, there are no published studies regarding sustained tissue loads during toilet sitting and their effects on tissue physiology. Here, the biomechanical and microcirculatory responses of the buttock tissues to toilet sitting were investigated using finite element modeling and cutaneous hemodynamic measurements, to explore the potential etiology of PrIs occurring on the toilet. We found that prolonged sitting on toilet seats involves a potential risk for PrI development, the extent of which is affected by the seat design. Additionally, we found that specialized toilet seat cushions are able to reduce this risk, by lowering instantaneous tissue exposures to internal stresses (by up to 88%) and maintaining reduced interface pressures. Furthermore, hemodynamic variables were altered during the toilet sitting; in particular, tcPO₂ was decreased by 49% ± 7% (44 ± 2[mmHg] to 22 ± 4[mmHg]) during sitting. The current study confirms that investing in expensive PrI prevention (PIP) products is likely to be ineffective for an immobilized patient who is left to sit on a bare toilet seat for long times. This argument highlights the need for a holistic-care approach, employing PIP devices that span across the entire environment where bodyweight forces apply to tissues.

Pressure injury prediction using diffusely scattered light

Pressure injuries (PIs) originate beneath the surface of the skin at the interface between bone and soft tissue. We used diffuse correlation spectroscopy (DCS) and diffuse near-infrared spectroscopy (DNIRS) to predict the development of PIs by measuring dermal and subcutaneous red cell motion and optical absorption and scattering properties in 11 spinal cord injury subjects with only nonbleachable redness in the sacrococcygeal area in a rehabilitation hospital and 20 healthy volunteers. A custom optical probe was developed to obtain continuous DCS and DNIRS data from sacrococcygeal tissue while the subjects were placed in supine and lateral positions to apply pressure from body weight and to release pressure, respectively. Rehabilitation patients were measured up to four times over a two-week period. Three rehabilitation patients developed open PIs (POs) within four weeks and eight patients did not (PNOs). Temporal correlation functions in the area of redness were significantly different ( p < 0.01 ) during both baseline and applied pressure stages for POs and PNOs. The results show that our optical method may be used for the early prediction of ulcer progression.

A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats

Deformation of skeletal muscle in the proximity of bony structures may lead to deep tissue injury category of pressure ulcers. Changes in mechanical properties have been proposed as a risk factor in the development of deep tissue injury and may be useful as a diagnostic tool for early detection. MRE allows for the estimation of mechanical properties of soft tissue through analysis of shear wave data. The shear waves originate from vibrations induced by an external actuator placed on the tissue surface. In this study a combined Magnetic Resonance (MR) compatible indentation and MR Elastography (MRE) setup is presented to study mechanical properties associated with deep tissue injury in rats. The proposed setup allows for MRE investigations combined with damage-inducing large strain indentation of the Tibialis Anterior muscle in the rat hind leg inside a small animal MR scanner. An alginate cast allowed proper fixation of the animal leg with anatomical perfect fit, provided boundary condition information for FEA and provided good susceptibility matching. MR Elastography data could be recorded for the Tibialis Anterior muscle prior to, during, and after indentation. A decaying shear wave with an average amplitude of approximately 2 μm propagated in the whole muscle. MRE elastograms representing local tissue shear storage modulus G_d showed significant increased mean values due to damage-inducing indentation (from 4.2 ± 0.1 kPa before to 5.1 ± 0.6 kPa after, p<0.05). The proposed setup enables controlled deformation under MRI-guidance, monitoring of the wound development by MRI, and quantification of tissue mechanical properties by MRE. We expect that improved knowledge of changes in soft tissue mechanical properties due to deep tissue injury, will provide new insights in the etiology of deep tissue injuries, skeletal muscle damage and other related muscle pathologies.

How does lateral tilting affect the internal strains in the sacral region of bed ridden patients? - A contribution to pressure ulcer prevention

BACKGROUND

Repositioning of individuals with reduced mobility and at risk of pressure ulcers is an essential preventive step. Manual or automatic lateral tilting is a way of doing this and the international guidelines propose a 30° to 40° side lying position. The goal of the present study was to determine the internal strains in individuals lying in a supine position and during tilting.

METHODS

Based on magnetic resonance imaging (MRI) of the sacral area of human volunteers, subject specific finite element models were developed. By comparing calculated contours of the skin, fat and muscle with MRI measurements on a flat surface the models were validated. A parameter study was performed to assess the sensitivity of the model for changes in material properties. Simulations were performed at tilting angles of volunteers between 0° and 45°.

FINDINGS

Subjects in a supine position or tilted have the highest strains in the muscle and fat. Tilting does affect the strain distribution, taking away the highest peak strains. There seems to exist an optimal tilting angle between 20° and 30°, which may vary depending on factors such as BMI of the subject and is in the current paper investigated only for the sacrum.

INTERPRETATION

The study shows that tilting indeed has a significant, positive influence on internal strains, which is important for the prevention of deep tissue injury. Additional studies are needed to draw conclusions about the greater trochanter area and the tissues around the shoulder.

Subepidermal moisture (SEM) and bioimpedance: a literature review of a novel method for early detection of pressure-induced tissue damage (pressure ulcers)

Current detection of pressure ulcers relies on visual and tactile changes at the skin surface, but physiological changes below the skin precede surface changes and have a significant impact on tissue health. Inflammatory and apoptotic/necrotic changes in the epidermal and dermal layers of the skin, such as changes in interstitial fluid (also known as subepidermal moisture (SEM)), may precede surface changes by 3–10 days. Those same epidermal and subepidermal changes result in changes in the electrical properties (bioimpedance) of the tissue, thereby presenting an objective, non‐invasive method for assessing tissue damage. Clinical studies of bioimpedance for the detection of pressure ulcers have demonstrated that changes in bioimpedance correlate with increasing severity of pressure ulcer stages. Studies have also demonstrated that at anatomical locations with pressure ulcers, bioimpedance varies with distance from the centre of the pressure ulcers. The SEM Scanner, a handheld medical device, offers an objective and reliable method for the assessment of local bioimpedance, and therefore, assessment of tissue damage before signs become visible to the unaided eye. This literature review summarises pressure ulcer pathophysiology, principles of bioimpedance and clinical research using bioimpedance technology to assess pressure ulcers.

A Multimodality Imaging and Software System for Combining an Anatomical and Physiological Assessment of Skin and Underlying Tissue Conditions

OBJECTIVE:

The timely and accurate assessment of skin and underlying tissue is crucial for making informed decisions relating to wound development and existing wounds. The study objective was to determine within- and between-reader agreement of Scout Visual-to-Thermal Overlay (WoundVision LLC, Indianapolis, Indiana) placement (moving the wound edge trace from the visual image onto the wound edge signature of the infrared image).

MATERIALS AND METHODS:

For establishing within- and between-reader agreement of the Scout Visual-to-Thermal Overlay feature, 5 different readers overlaid a wound edge trace from the visual image and placed it onto the congruent thermal representation of the wound on a thermal image 3 independent times. Forty different wound image pairs were evaluated by each reader. All readers were trained by the same trainer on the operation of the Scout prior to using the software features. The Scout Visual-to-Thermal Overlay feature allows clinicians to use an anatomical measurement of the wound on the visual image (area and perimeter) to extract a congruent physiological measurement of the wound on the thermal image (thermal intensity variation data) by taking the wound edge trace from the visual image and overlaying it onto the corresponding thermal signature of the same wound edge.

RESULTS:

The results are very similar both within- and between-readers. The coefficient of variation (CV) for the mean PV both within- and between-readers averages less than 1%, 0.89 and 0.77 respectively. When converted into degrees Celsius across all 5 readers and all 3 wound replicates, the average temperature differential is 0.28° C (Table 2). The largest difference observed was 0.63° C and the smallest difference observed was 0.04° C.

CONCLUSIONS:

The Scout software’s Visual-to-Thermal Overlay procedure, as implemented in this study, is very precise. This study demonstrates that the thermal signature of wounds may be delineated repeatedly by the same operator and reproducibly by different operators. Thus, clinicians can integrate a criterion standard visual (anatomical) assessment with a congruent physiological assessment to provide them with knowledge relating to the presence or absence of blood flow, perfusion, and metabolic activity in the wound, periwound, and wound site.

Pressure Combined with Ischemia/Reperfusion Injury Induces Deep Tissue Injury via Endoplasmic Reticulum Stress in a Rat Pressure Ulcer Model

Pressure ulcer is a complex and significant health problem in long-term bedridden patients, and there is currently no effective treatment or efficient prevention method. Furthermore, the molecular mechanisms and pathogenesis contributing to the deep injury of pressure ulcers are unclear. The aim of the study was to explore the role of endoplasmic reticulum (ER) stress and Akt/GSK3β signaling in pressure ulcers. A model of pressure-induced deep tissue injury in adult Sprague-Dawley rats was established. Rats were treated with 2-h compression and subsequent 0.5-h release for various cycles. After recovery, the tissue in the compressed regions was collected for further analysis. The compressed muscle tissues showed clear cellular degenerative features. First, the expression levels of ER stress proteins GRP78, CHOP, and caspase-12 were generally increased compared to those in the control. Phosphorylated Akt and phosphorylated GSK3β were upregulated in the beginning of muscle compression, and immediately significantly decreased at the initiation of ischemia-reperfusion injury in compressed muscles tissue. These data show that ER stress may be involved in the underlying mechanisms of cell degeneration after pressure ulcers and that the Akt/GSK3β signal pathway may play an important role in deep tissue injury induced by pressure and ischemia/reperfusion.

Pressure ulcer risk of patient handling sling use

Patient handling slings and lifts reduce the risk of musculoskeletal injuries for healthcare providers. However, no published evidence exists of their safety with respect to pressure ulceration for vulnerable populations, specifically persons with spinal cord injury, nor do any studies compare slings for pressure distribution. High-resolution interface pressure mapping was used to describe and quantify risks associated with pressure ulceration due to normal forces and identify at-risk anatomical locations. We evaluated 23 patient handling slings with 4 nondisabled adults. Sling-participant interface pressures were recorded while participants lay supine on a hospital bed and while suspended during typical patient transfers. Sling-participant interface pressures were greatest while suspended for all seated and supine slings and exceeded 200 mm Hg for all seated slings. Interface pressures were greatest along the sling seams (edges), regardless of position or sling type. The anatomical areas most at risk while participants were suspended in seated slings were the posterior upper and lower thighs. For supine slings, the perisacral area, ischial tuberosities, and greater trochanters were most at risk. The duration of time spent in slings, especially while suspended, should be limited.

Deformation of the gluteal soft tissues during sitting

BACKGROUND

Excessive deformation of soft tissues is considered to be one of the major contributing factors to discomfort and injury for individuals who sit for long periods of time. Soft tissue deformation in research has been measured under the assumption that tissues deform uniaxially below the ischium, with very small or negligible deformations taking place in other directions. Therefore, this study describes the deformation of the gluteus maximus muscle and surrounding fat tissues in the buttock region for seated subjects.

METHODS

In vivo measurements of the deformation for the gluteal soft tissues were obtained from MRI scans of six seated subjects. Each subject was scanned in weight-bearing and non-weight-bearing sitting postures using a Positional MRI scanner (Fonar 0.6 Tesla Indomitable™). Deformations were measured below the ischium and the proximal femur. Deformation of the gluteus maximus was also measured in the distal direction along the thigh for each subject.

FINDINGS

Our data suggest that soft tissues undergo three-dimensional deformation with considerable components below the ischium (mean of 21.4mm) and in the distal direction along the thigh (mean of 20.3mm). Differences in muscle deformation below the ischium were also observed between obese (mean of 27.4mm) and non-obese subjects (mean of 16.5mm).

INTERPRETATION

Findings of this study demonstrate that tissue deformations in sitting include complex three-dimensional motions that are not well approximated by two-dimensional models.