Aetiology of pressure sores

A systematic review on the impact of sub-epidermal moisture assessments on pressure ulcer/injury care delivery pathways

To assess all published studies which describe what happens to the delivery of pressure ulcer/injury (PI/PU) care pathways as a result of detecting raised sub-epidermal moisture (SEM) delta (∆ ≥ 0.6). We undertook a systematic review of the literature, and included original research studies using either a prospective or retrospective study design that report the impact that assessment using SEM assessments have on healthcare practitioners' delivery of PI/PU care pathways in adults at risk of developing PI/PUs. The review protocol was registered on PROSPERO (CRD42023416975). A literature search was conducted in May 2023, using PubMed, CINAHL, Scopus, Cochrane, EMBASE, Web of Science and Science Direct databases. Data were extracted using a data extraction tool including elements such as country, setting, sample size, intervention, control and quality appraisal was undertaken using the Evidence-based Librarianship. We identified nine papers published between 2017 and 2022. The majority of these studies were conducted in England (n = 6; 67%). The systematic review included studies conducted across multiple care settings including acute care, medical-surgical units, and palliative care, highlighting the importance of PI/PU prevention and management across diverse patient populations. The PI/PU care pathways implemented in the studies varied, but commonly included elements such as the application or increased use of pressure-redistributing mattresses/cushions, implementation of repositioning plans, management of incontinence and moisture, regular skin inspection, and assessment of patient mobility. Out of the nine studies identified, seven reported PI/PU incidence. A meta-analysis of seven studies (N = 18 451) demonstrated a statistically significant reduction in visual PI/PU development in favour of SEM-guided care pathways compared to usual care (the odds ratio = 0.36 [95% confidence interval: 0.24-0.53, p < 0.00001]). This systematic review provides evidence that implementing SEM assessments in patients at risk of developing PI/PUs prompts anatomy-specific clinical actions. The subsequent implementation of enhanced and targeted skin care interventions leads to consistent and sustained reductions in hospital-acquired PU incidence. The findings emphasise the importance of incorporating SEM assessments as part of comprehensive PI/PU prevention strategies in all care settings and patient populations. This systematic review is limited by the predominance of observational studies and variable study quality. Future research should focus on randomised trials in different care settings that monitor the efficacy of preventive interventions and their impact in reducing PI/PU incidence when implemented based on SEM assessments.

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.

The relationship between common risk factors and the pathology of pressure ulcer development: a systematic review

OBJECTIVE

The aim of this systematic review was to examine the associations and relationship between commonly cited risk factors and the pathology of pressure ulcer (PU) development.

METHOD

Using systematic review methodology, original research studies, prospective design and human studies written in English were included. The search was conducted in March 2018, using Ovid, Ovid EMBASE and CINAHL databases. Data were extracted using a pre-designed extraction tool and all included studies were quality appraised using the evidence-based librarianship critical appraisal.

RESULTS

A total of 382 records were identified, of which five met the inclusion criteria. The studies were conducted between 1994 and 2017. Most studies were conducted in hospital and geriatric wards. The mean sample size was 96±145.7 participants. Ischaemia, recovery of blood flow and pathological impact of pressure and shear was mainly found as the cited risk factor and PU aetiology.

CONCLUSION

This review systematically analysed five papers exploring the relationship between risk factors for PU development and aetiology. It identified many risk factors and underlying pathological mechanisms that interact in the development of PU including ischaemia, stress, recovery of blood flow, tissue hypoxia and the pathological impact of pressure and shear. There are several pathways in which these pathological mechanisms contribute to PU development and identifying these could establish potential ways of preventing or treating the development of PU for patients.

Exploring the role of transtibial prosthetic use in deep tissue injury development: a scoping review

Background

The soft tissue of the residual limb in transtibial prosthetic users encounters unique biomechanical challenges. Although not intended to tolerate high loads and deformation, it becomes a weight-bearing structure within the residuum-prosthesis-complex. Consequently, deep soft tissue layers may be damaged, resulting in Deep Tissue Injury (DTI). Whilst considerable effort has gone into DTI research on immobilised individuals, only little is known about the aetiology and population-specific risk factors in amputees. This scoping review maps out and critically appraises existing research on DTI in lower-limb prosthetic users according to (1) the population-specific aetiology, (2) risk factors, and (3) methodologies to investigate both.

Results

A systematic search within the databases Pubmed, Ovid Excerpta Medica, and Scopus identified 16 English-language studies. The results indicate that prosthetic users may be at risk for DTI during various loading scenarios. This is influenced by individual surgical, morphological, and physiological determinants, as well as the choice of prosthetic componentry. However, methodological limitations, high inter-patient variability, and small sample sizes complicate the interpretation of outcome measures. Additionally, fundamental research on cell and tissue reactions to dynamic loading and on prosthesis-induced alterations of the vascular and lymphatic supply is missing.

Conclusion

We therefore recommend increased interdisciplinary research endeavours with a focus on prosthesis-related experimental design to widen our understanding of DTI. The results have the potential to initiate much-needed clinical advances in surgical and prosthetic practice and inform future pressure ulcer classifications and guidelines.

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

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

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.

Strengthening of C2C12 mouse myoblasts against compression damage by mild cyclic compressive stimulation

Deep tissue injury (DTI) is a severe kind of pressure ulcers formed by sustained deformation of muscle tissues over bony prominences. As a major clinical issue, DTI affects people with physical disabilities, and is obviously related to the load-bearing capacity of muscle cells in various in-vivo conditions. It is important to provide a preventive approach to help muscle cells from being damaged by compressive stress. In this study, we hypothesized that cyclic compressive stimulation could strengthen muscle cells against compressive damage and enhance the cell plasma membrane resealing capability. Monolayer of myoblasts was cultured in the cell culture dish covered by a cylinder 0.5% agarose gel. The platen indenter was applied with 20% strain on the agarose gel in the Mach-1 micromechanical system. The vibration was 1Hz sinusoidal function with amplitude 0.2% strain based on 20% gel strain. Cyclic compressive stimulation for 2h could enhance the compressive stress damage threshold of muscle cells, the muscle cell plasma membrane resealing ratio and viability of muscle cell under static loading as preventive approach. This approach might help to reduce the risk of DTI in clinic.

Effects of Biowastes Released by Mechanically Damaged Muscle Cells on the Propagation of Deep Tissue Injury: A Multiphysics Study

Deep tissue injuries occur in muscle tissues around bony prominences under mechanical loading leading to severe pressure ulcers. Tissue compression can potentially compromise lymphatic transport and cause accumulation of metabolic biowastes, which may cause further cell damage under continuous mechanical loading. In this study, we hypothesized that biowastes released by mechanically damaged muscle cells could be toxic to the surrounding muscle cells and could compromise the capability of the surrounding muscle cells to withstand further mechanical loadings. In vitro, we applied prolonged low compressive stress (PLCS) and short-term high compressive stress to myoblasts to cause cell damage and collected the biowastes released by the damaged cells under the respective loading scenarios. In silico, we used COMSOL to simulate the compressive stress distribution and the diffusion of biowastes in a semi-3D buttock finite element model. In vitro results showed that biowastes collected from cells damaged under PLCS were more toxic and could compromise the capability of normal myoblasts to resist compressive damage. In silico results showed that higher biowastes diffusion coefficient, higher biowastes release rate, lower biowastes tolerance threshold and earlier timeline of releasing biowastes would cause faster propagation of tissue damage. This study highlighted the importance of biowastes in the development of deep tissue injury to clinical pressure ulcers under prolonged skeletal compression.

The Effects of Different Lying Positions on Interface Pressure, Skin Temperature, and Tissue Blood Flow in Nursing Home Residents

Background:

Although repositioning is considered an important intervention to prevent pressure ulcers, tissue response during loading in different lying positions has not been adequately explored.

Aim:

To compare the effects of different lying positions on interface pressure, skin temperature, and tissue blood flow in nursing home residents.

Method:

From May 2011 to August 2012, interface pressure, skin temperature, and blood flow at three tissue depths were measured for 1 hr over the sacrum in 30° supine tilt and 0° supine positions and over the trochanter major in 30° lateral and 90° lateral positions in 25 residents aged 65 years or older. Measurement of interface pressure was accomplished using a pneumatic pressure transmitter connected to a digital manometer, skin temperature using a temperature sensor, and blood flow using photoplethysmography and laser Doppler flowmetry.

Results:

Interface pressure was significantly higher in the 0° supine and 90° lateral positions than in 30° supine tilt and 30° lateral positions. The mean skin temperature increased from baseline in all positions. Blood flow was significantly higher in the 30° supine tilt position compared to the other positions. A hyperemic response in the post pressure period was seen at almost all tissue depths and positions.

Conclusion:

The 30° supine tilt position generated less interface pressure and allowed greater tissue perfusion, suggesting that this position is the most beneficial.

Report on a clinical evaluation of the KerraPro Heel silicone heel pad

Heels are at increased risk of injury due to the posterior prominence and lack of padding over the calcaneus. Pressure injuries, once established, are extremely costly, both in terms of the detrimental effect on psychosocial wellbeing and threat to life, as well as financially due to length of hospital stay and resources used to heal the wounds. A new and inexpensive silicone heel pad has been designed to simplify the necessary decisions and to address the problems associated with pressure injuries to the heels. This article will describe an observational evaluation of the product. KerraPro Heel pads were evaluated in two separate cohorts of 17 participants over a 4-week period with the primary aim to evaluate the efficacy of the product in preventing and alleviating pressure injuries on the heels. All participants had been reported as 'at risk' or 'at high risk' of pressure injury to the heels and had a history of developing such lesions. The KerraPro heel pads were compared with the participant's standard protocol. The outcome of the evaluation demonstrated the effectiveness of the KerraPro Heel pads in the prevention and treatment of heel pressure injuries.

Wound healing and nutrition: going beyond dressings with a balanced care plan

As the largest organ of the body, the human skin protects all subcutaneous tissues. Despite its many attributes, the skin is vulnerable to pressure ulcers. The number of pressure ulcers and venous leg ulcers is on the rise, but healing rates have not improved over the past decade. The reason may be a tendency to focus on one or two fundamentals of wound healing, but not on all 3 fundamentals equally. The 3 fundamentals of wound healing are (1) pressure relief and nursing care, (2) dressings, and (3) nutrition. Nutrition is the area that is most often overlooked, which commonly causes the care plan to be out of balance. In the United States, few clinicians would consider malnutrition to be an issue in the homecare and long-term care setting, yet nutritional status and risk for pressure ulcer formation are well documented and strongly correlated. Our aging population will continue to survive previously catastrophic events, only to present with pressure ulcers or the potential for developing pressure ulcers. Clinicians caring for residents with pressure ulcers must strike a balance between pressure relief, dressings, and nutrition. Functional gastrointestinal-tract impairments must be diagnosed and addressed. Wounds must be treated aggressively with high-protein calorically-balanced diets because wounds heal from the inside out.

ROHO Dry floatation technology: implications for clinical practice

This article discusses the aetiology of pressure ulcers, the clinical and financial cost of pressure ulcer prevention and the need for pressure reducing equipment. The role of Dry floatation in pressure ulcer prevention and management is explored. How Dry floatation technology works is discussed and its use within clinical practice is highlighted. The evidence to support Dry floatation is presented.

Assessment of patient support surfaces: principle, practice and limitations

Pressure ulcers cause great pain and suffering to patients as well as unnecessary strain on nursing staff. Their treatment is both costly and time consuming. Every effort therefore should be directed towards their prevention. Understanding of the aetiology of pressure ulcers is still incomplete and assessment of devices aimed at prevention is difficult. Over the years, numerous parameters, including interface pressure and transcutaneous blood gas measurements, have been used to evaluate mattresses and cushions. However, the quality of the data gathered is variable and its clinical interpretation remains unsatisfactory. It could be said that the science of evaluation of support surfaces is still at a formative stage, as clinical validation of many of the approaches has yet to be carried out.

A new predictive indicator for development of pressure ulcers in bedridden patients based on common laboratory tests results

Background:

Various scales have been devised to predict development of pressure ulcers on the basis of clinical and laboratory data, such as the Braden Scale (Braden score), which is used to monitor activity and skin conditions of bedridden patients. However, none of these scales facilitates clinically reliable prediction.

Aims:

To develop a clinical laboratory data-based predictive equation for the development of pressure ulcers.

Methods:

Subjects were 149 hospitalised patients with respiratory disorders who were monitored for the development of pressure ulcers over a 3-month period. The proportional hazards model (Cox regression) was used to analyse the results of 12 basic laboratory tests on the day of hospitalisation in comparison with Braden score.

Results:

Pressure ulcers developed in 38 patients within the study period. A Cox regression model consisting solely of Braden scale items showed that none of these items contributed to significantly predicting pressure ulcers. Rather, a combination of haemoglobin (Hb), C-reactive protein (CRP), albumin (Alb), age, and gender produced the best model for prediction. Using the set of explanatory variables, we created a new indicator based on a multiple logistic regression equation. The new indicator showed high sensitivity (0.73) and specificity (0.70), and its diagnostic power was higher than that of Alb, Hb, CRP, or the Braden score alone.

Conclusions:

The new indicator may become a more useful clinical tool for predicting presser ulcers than Braden score. The new indicator warrants verification studies to facilitate its clinical implementation in the future.

Softform Premier Active Mattress: a novel step-up/step-down approach

In the UK it is estimated that as many as 412,000 patients who are already ill will develop pressure ulcers (Bennett et al, 2004), which are an unnecessary and expensive complication to treat (Hitch, 1995). One way to try and reduce these risks is by investing in suitable mattresses. The author's investigations into existing mattress stock in the years 1996-97 illustrated the inadequacy of the NHS standard mattress (Santy, 1995; Fox, 1997). Investigators (e.g. Rithalia, 1996) were recognizing the inadequacy of the pink marbled standard NHS foam mattress for pressure reduction (Medical Device Directorate, 1993; Dunford, 1994) which included reports necessary to help develop guidelines in pressure ulcer prevention and management (Coull, 2004), as well as make value-for-money recommendations about product purchases (Fletcher et al, 1994; Value For Money Update, 1994; Cullum et al, 1995).

Evaluation of antidecubitus mattresses

Pressure sores are a current problem in hospitals and care of the elderly, leading to protracted hospital stays and a high care burden. The trauma for the patients is severe, and the cost of pressure sore prevention and treatment, is considerable. Antidecubitus mattresses are used for prevention and in treatment, but they also contribute to the cost of treating pressure sores. The problem highlighted in the review is that the mattresses' effectiveness in preventing and treating pressure sores has not been sufficiently evaluated. When antidecubitus mattresses are evaluated, it is often only with regard to aspects of the interface pressure and the mattresses' ability to redistribute the pressure. The review points out the important observation that, to be able to evaluate the efficacy of the antidecubitus mattress, the mattress's effect on tissue viability needs to be studied. The parameters that ought to be considered when evaluating a support surface are: interface pressure, pressure and blood flow distribution, temperature and humidity in the skin-support surface interface. The authors propose that the effect on tissue viability of external loading can be assessed by simultaneous measurement of the interface pressure and tissue perfusion.

Compression-induced deep tissue injury examined with magnetic resonance imaging and histology

The underlying mechanisms leading to deep tissue injury after sustained compressive loading are not well understood. It is hypothesized that initial damage to muscle fibers is induced mechanically by local excessive deformation. Therefore, in this study, an animal model was used to study early damage after compressive loading to elucidate on the damage mechanisms leading to deep pressure ulcers. The tibialis anterior of Brown-Norway rats was loaded for 2 h by means of an indenter. Experiments were performed in a magnetic resonance (MR)-compatible loading device. Muscle tissue was evaluated with transverse relaxation time (T2)-weighted MRI both during loading and up to 20 h after load removal. In addition, a detailed examination of the histopathology was performed at several time points (1, 4, and 20 h) after unloading. Results demonstrated that, immediately after unloading, T2-weighted MR images showed localized areas with increased signal intensity. Histological examination at 1 and 4 h after unloading showed large necrotic regions with complete disorganization of the internal structure of the muscle fibers. Hypercontraction zones were found bilateral to the necrotic zone. Twenty hours after unloading, an extensive inflammatory response was observed. The proposed relevance of large deformation was demonstrated by the location of damage indicated by T2-weighted MRI and the histological appearance of the compressed tissues. Differences in damage development distal and proximal to the indenter position suggested a contribution of perfusion status in the measured tissue changes that, however, appeared be to reversible.

A guide to evaluating different wheelchair seat cushions

Over the years, there has been a considerable increase in the number and variety of wheelchair seat cushions. People required to select a cushion are faced with a confusing and often misleading array of commercial literature. The cost of these products range from less than £100 to several hundred pounds, so the importance of a logical approach to their selection cannot be overstated. Inappropriate selection not only wastes capital resources, but it can also be very harmful to the patient.

Although the effectiveness of a wheelchair cushion is best evaluated through clinical trials, these are expensive to conduct and in the case of new products, such evidence is not readily available. In order to overcome this drawback, researchers have developed experimental methods of evaluation based upon existing knowledge of pressure ulcer aetiology. This article describes the most common methods, along with a new technique known as pressure relief index.

Compression-induced damage in a muscle cell model in vitro

Soft tissue breakdown can be initiated at the muscle layer associated with bony prominences, leading to the development of pressure ulcers. Both the magnitude and duration of pressure are important factors in this breakdown process. The present study utilizes a physical model, incorporating C2C12 mouse myoblasts in a homogeneous agarose gel, to examine the damaging effects of prolonged applied pressure. Identical cylindrical cores cut from the agarose/cell suspension were subjected to two separate compressive strains, of 10 and 20 per cent. The strain was applied for time periods ranging from 0.5 to 12 hours, using a specially designed loading apparatus. After each compression period, sections taken from the central horizontal plane of the individual constructs were stained using either haematoxylin and eosin or with the fluorescent probes, Calcein AM and ethidium homodimer-1, and assessed for cell damage. It was found that constructs subjected to the higher strain values demonstrated significantly higher values of non-viable cells for equivalent time points compared to the unstrained constructs. Further analysis on sections using the DNA nick-translation method suggested that this increase was primarily due to apoptosis. These findings imply a relationship between the duration of applied compression and damage to muscle cells seeded in the gel, which was particularly apparent at the strain level of 20 per cent, equivalent to a clinically relevant pressure of 32 mmHg (4.3 kPa). Such an approach might be useful in establishing damage threshold levels at a cellular level.

In Vivo Muscle Stiffening Under Bone Compression Promotes Deep Pressure Sores

Pressure sores (PS) in deep muscles are potentially fatal and are considered one of the most costly complications in spinal cord injury patients. We hypothesize that continuous compression of the longissimus and gluteus muscles by the sacral and ischial bones during wheelchair sitting increases muscle stiffness around the bone-muscle interface over time, thereby causing muscles to bear intensified stresses in relentlessly widening regions, in a positive-feedback injury spiral. In this study, we measured long-term shear moduli of muscle tissue in vivo in rats after applying compression (35 KPa or 70 KPa for 1∕4–2 h, N=32), and evaluated tissue viability in matched groups (using phosphotungstic acid hematoxylin histology, N=10). We found significant (1.8-fold to 3.3-fold, p<0.05) stiffening of muscle tissue in vivo in muscles subjected to 35 KPa for 30 min or over, and in muscles subjected to 70 KPa for 15 min or over. By incorporating this effect into a finite element (FE) model of the buttocks of a wheelchair user we identified a mechanical stress wave which spreads from the bone-muscle interface outward through longissimus muscle tissue. After 4 h of FE simulated motionlessness, 50%–60% of the cross section of the longissimus was exposed to compressive stresses of 35 KPa or over (shown to induce cell death in rat muscle within 15 min). During these 4 h, the mean compressive stress across the transverse cross section of the longissimus increased by 30%–40%. The identification of the stiffening-stress-cell-death injury spiral developing during the initial 30 min of motionless sitting provides new mechanistic insight into deep PS formation and calls for reevaluation of the 1 h repositioning cycle recommended by the U.S. Department of Health.

An online ordering system for therapy beds and mattresses

Within this article, the authors have put forward a solution to keep track of pressure-relieving devices using internet-based secure online systems. In partnership with a therapy bed company they set up a system that was able to manage and monitor the requirements of their trust and ensure that products are used for patients who most need them. In using these systems they were also able to gather real-time data on usage and costs as well as time-dependent analysis. The system has also allowed a means of gathering outcome measurement of all products in use. Over a 6-month period the authors have shown how a forecasted 18% budget deficit has been turned into a 10% under spend of the overall budget. It is suggested that these systems could be one way of managing the pressure-relieving needs of hospital trusts ensuring both clinical effectiveness and cost-benefit.

A practical guide to the provision of mattresses and cushions to relieve pressure

Pressure damage is largely preventable, but if allowed to develop, individuals have the potential to suffer pain, indignity and even death. Pressure-relieving equipment is available to people at risk of pressure damage. Selection of suitable support surfaces must be based on identified criteria following holistic assessment.

This article aims to provide the reader with a general guide to the provision of pressure-relieving support surfaces. As pressure damage can occur both in the bed and the chair, the qualities of both mattresses and cushions will be discussed.

Russka pressure-relieving low air-loss mattress system

Pressure ulcers are distressing, frequently occur in immobile and malnourished patients and the cost to patients in terms of pain and anguish must be a prime consideration. There is little information on the incidence and prevalence of pressure ulcer development within the independent sector, as this is difficult to obtain. However, with advances in treatment and technology, combined with more people with complex and multiple needs being cared for at home, the requirement for specialist pressure-relieving support surfaces in the community is increasing. This article reviews the need for clinical and cost-effective pressure-relieving surface solutions in the community and introduces the concept of the Russka pressure-relieving low air-loss system.

Defined and refined: criteria for identifying wound infection revisited

Clinical criteria for the identification of wound infection are regularly based on a list created by Cutting and Harding (1994). This list was established from empirical data generated in a large, multidisciplinary clinical practice, and is now widely accepted as a seminal article in wound care. Both Cutting (1998) and Gardner et al (2001) have conducted validation exercises on these wound infection criteria, based on the assumption that the criteria broadly apply to most wound types. Although many of the original criteria do apply across the spectrum of wound types, the major categories of wounds should be considered separately to avoid the possibility of overlooking the presence of infection. The focus of this article is a review of the published literature on wound infection criteria for acute and surgical wounds, diabetic foot ulcers, venous and arterial leg ulcers, pressure ulcers and burns. All known criteria for each wound type are presented, as well as an outline of the ongoing research project to refine the criteria by wound type using a Delphi panel technique. No attempt has been made to correlate visual signs and symptoms with microbiological sampling techniques. It is clear that there are subtle variations between infection criteria for wound types and that these should be recognized if treatment is to be given appropriately and promptly, and morbidity avoided.

Quantifying pressure sore-related muscle damage using high-resolution MRI

To obtain insight into the etiology of deep pressure sores, understanding of the relationship between prolonged transverse loading and local muscle damage is required. To date, the amount and location of muscle damage have been determined by histological examination. In the present study, we determined whether T2-weighted high-resolution magnetic resonance imaging (MRI) can also be applied to evaluate muscle tissue after prolonged transverse loading. The tibialis anterior muscle and overlying skin in the right hindlimbs of five rats were compressed between an indenter and the tibia. The in vivo magnetic resonance images of the loaded and contralateral hindlimbs were obtained 24 h after load application. The tibialis anterior muscles were then processed for histological examination. In the magnetic resonance images of all five loaded hindlimbs, signal intensity appeared higher in the loaded regions of the muscle compared with the unloaded regions. The location of the higher signal intensity coincided with the location of damage assessed from histology. Also the amount of damage determined with MRI was in good agreement with the amount of damage assessed from histological examination. Because MRI is nondestructive, it is a promising alternative for histology in research on pressure sore etiology, especially in follow-up studies to evaluate the development of muscle damage in time and in clinical studies.

The QUATTRO ACUTE mattress and pressure ulcer prevention

There are a plethora of mattresses on the market and nurses are not always sure which mattress to select for each individual patient. This article outlines the issues in preventing and understanding pressure ulcers and the performance of the QUATTRO ACUTE trade mark mattress, manufactured by Talley Medical.

Can loaded interface characteristics influence strain distributions in muscle adjacent to bony prominences?

Pressure distributions at the interface between skin and supporting tissues are used in design of supporting surfaces like beds, wheel chairs, prostheses and in sales brochures to support commercial products. The reasoning behind this is, that equal pressure distributions in the absence of high pressure gradients is assumed to minimise the risk of developing pressure sores. Notwithstanding the difficulty in performing reproducible and accurate pressure measurements, the question arises if the interface pressure distribution is representative of the internal mechanical state of the soft tissues involved. The paper describes a study of the mechanical condition of a supported buttock contact, depending on cushion properties, relative properties of tissue layers and friction. Numerical, mechanical simulations of a buttock on a supporting cushion are described. The ischial tuberosity is modelled as a rigid body, whereas the overlying muscle, fat and skin layers are modelled as a non-linear Ogden material. Material parameters and thickness of the fat layer are varied. Coulomb friction between buttock and cushion is modelled with different values of the friction coefficient. Moreover, the thickness and properties of the cushion are varied. High shear strains are found in the muscle near the bony prominence and the fat layer near the symmetry line. The performed parameter variations lead to large differences in shear strain in the fat layer but relatively small variations in the skeletal muscle. Even with a soft cushion, leading to a high reduction of the interface pressure the deformation of the skeletal muscle near the bone is high enough to form a risk, which is a clear argument that interface pressures alone are not sufficient to evaluate supporting surfaces.

Deep Cell Prime: preventing and healing pressure ulcers

One method of pressure ulcer prevention is the use of alternating pressure air mattresses. This article outlines the Talley Medical Deep Cell Prime trade mark mattress replacement system, which is used in conjunction with Trinity HR Dynamic trade mark cushion in order to provide 24-hour pressure relief.

Best practice statement of the prevention of pressure ulcers

The Nursing and Midwifery Development Unit, Scotland, has developed a range of best practice statements, one of which relates to the prevention of pressure ulcers. The development of the statement involved achieving a consensus as to what constituted best practice in this field among the 30 nurse specialists in tissue viability working within Scotland. The statement aims to provide practical, relevant and factual information to guide pressure ulcer prevention practice.

SuperSkin: the management of skin susceptible to breakdown

Few studies have been undertaken in the area of skin protection, even though maintaining tissue viability in the event of incontinence, shear forces and the potential for exudate to macerate periwound areas remains a challenge for any nurse caring for patients. This article outlines and discusses the problems associated with overhydrated tissues and shear forces and the potential for SuperSkin liquid film dressing, marketed by CliniMed, to provide a solution.

Effects of warming therapy on pressure ulcers--a randomized trial

Postoperative pressure ulcers are a common and expensive problem. Intraoperative hypothermia also is a common problem and may have a connection with impaired tissue viability. Researchers in this study hypothesized that intraoperative control of hypothermia may reduce the incidence of postoperative pressure ulcers. A randomized clinical trial (n = 338) was used to test the effects of using forced air warming therapy versus standard care. Results indicated an absolute risk reduction in pressure ulcers of 4.8% (i.e., 10.4% to 5.6%) with a relative risk reduction of 46% in patients who received warming therapy. Although not reaching statistical significance, the clinical significance of almost halving the pressure ulcer rate is important. A correlation between body temperature and postoperative pressure ulcers was established.

Quantification and localisation of damage in rat muscles after controlled loading; a new approach to study the aetiology of pressure sores

To obtain more insight in the aetiology of deep pressure sores, an animal model was developed to relate controlled external loading to local muscle damage. The tibialis anterior muscle (TA) and overlying skin of a rat were compressed between indentor and tibia. Loads of 10, 70 and 250kPa at skin surface were applied for 2 or 6h. During half of the 10 and 250kPa experiments interstitial fluid pressure (IFP) in the TA was measured. The TAs were excised 24h after load application. Both amount and location of damage were assessed by histological examination using a semi-automated image-processing program. In six of eleven loaded muscles damage was found. The damage was located from superficial to deep muscle tissue in a zone never exceeding the diameter of the indentor. The IFP measurements interfered with the occurrence of damage; application of 10 and 70kPa loads only caused damage when combined with IFP measurements, whereas IFP measurements increased damage at 250kPa loads. The results showed that the developed animal model can be used to provoke local damage by applying a controlled load and that the amount and location of damage can be assessed using the newly developed techniques.

Obstetric care. Is there risk of pressure damage after epidural anaesthesia?

Anecdotal evidence suggests that there is an increase in the incidence of pressure damage to women in labour. This appears to be associated with epidural anaesthesia. Epidural anaesthesia used to control pain in childbirth causes loss of sensation and a degree of motor block, which removes the women's reflexes and ability to reposition to prevent pressure damage. The large amount of fluids present during childbirth may also increase the risk of pressure damage, especially in association with shear and friction. A combination of unfamiliarity of pressure ulcer prevention techniques among midwives, and the type of delivery room equipment, that is currently available, may leave young healthy women at risk of developing pressure ulcers.

A difficult wound to treat?

I was referred a patient from a ward that was having difficulty managing this wound (Fig 1). The patient is paralysed down one side and has an acquired blood-borne disorder. The patient cannot control their body functions and has an indwelling catheter. On examination the wound was malodorous, with a diameter of 8cm and a depth of 4.5cm. The injury had occurred on transfer to the hospital. At first it manifested itself as a small nick on the skin with surrounding discoloration. The patient was on a pressure-relieving bed borrowed from the tissue viability team and had been in the ward for eight weeks. Wound swabs were taken. The patient was sensitive to vancomycin, penicillin and metronidazole. Taking into account the blood-borne disorder, how would you treat this wound and what form of secondary dressing would you use? There are problems with large amounts of exudate.

The new QUATTRO PLUS mattress replacement system

Since the early development of alternating pressure air mattresses (APAMs) there have been regular alterations in design. These designs have led to improved reliability and performance. This article outlines the changes made by Talley Medical to the QUATTRO PLUS replacement mattress. Improved safety features and design modifications continue the process commenced many years ago which has seen the use of alternating pressure air mattresses become widespread throughout the UK.

Prognostic factors associated with pressure sore development in the immediate post-operative period

The purpose of this study was to identify variables associated with post-operative pressure sore incidence. The data were derived from a sequential, double triangular, randomised, blinded, controlled trial of the intra-operative use of a visco-elastic polymer pad conducted at two centres. Of 446 surgical patients recruited the main endpoint was assessed for 416 patients of whom 65 (15.6%) had a post-operative pressure sore. Analysis determined that the probability of a patient developing a pressure sore was associated with increased number of hypotensive episodes and mean core temperature during surgery, and reduced mobility Day 1 post-operatively. The development of a probability equation illustrates the future potential of prognostic factor research in the development of risk assessment tools and their application within clinical settings.

Do pressure relief cushions really relieve pressure?

In a laboratory setting, interface pressures of 29 cushions and a sheepskin were measured on 20 healthy volunteers. Each participant was seated in an upright posture with their back against the back of the chair, hands resting on the lap, knees bent at an angle of 90 degrees, and feet resting on the floor. Only 13 cushions had any pressure-reducing effect. Gel cushions and sheepskins appear to have no pressure-reducing effect. The category of foam includes both cushions that reduce interface pressure very well and cushions that increase interface pressure. The lowest interface pressures were measured on air cushions and on some foam cushions.

A clinical evaluation of an alternating-pressure mattress replacement system in hospital and residential care settings

An observational study was carried out to compare wound healing on alternating-pressure mattress replacement systems (APMRS) and other surfaces in an elderly population in acute and residential care settings. Subjects were assessed for the reduction in their pressure ulcers at approximately two weeks and per day, and a visual analogue scale was used to record the patients' comfort. Seven and ten subjects were allocated to the Nimbus III APMRS (Huntleigh Healthcare Ltd) in the hospital and residential care settings respectively. There was no significant difference in the healing of the subjects' sores in the two areas either at two weeks or per day. Five people were allocated to control surfaces in the hospital setting (mainly APMRS; Pegasus Airwave, Pegasus Egerton) and ten in the residential care setting (mainly alternating-pressure overlays; AlphaXcell, Huntleigh Healthcare Ltd). There was no significant difference in the healing of subjects' sores in the two areas, either at two weeks or per day. The trial APMRS was found to be equally comfortable in either setting, and in both settings the control surfaces were not regarded as significantly different in terms of comfort. These findings, from a small sample, promote discussion about the use of pressure-relieving equipment in settings where there are older people who may be at particular risk from pressure damage and where nursing interventions are less intensive and routine.

Hospital bed mattresses: an overview of technical aspects

Mattresses designed for clinical applications are deceptively simple pieces of equipment. Their primary function is to comfortably support the patient in an appropriate position. However, there are many other technical factors that affect the quality of the support surfaces. In this paper we discuss the basic functions that mattresses should fulfil, explain some of the underlying mechanics and discuss CE marking and other standards.

Blanching and non-blanching hyperaemia

A review of terms and definitions involved in the identification of risk of pressure ulcer development

Physiology of the skin and prevention of pressure sores

Historically, pressure sores have been seen as a nursing problem, and still are to a certain extent today. Nurses therefore need to have a comprehensive understanding of the physiology of the skin to assist them in preventing and treating pressure sores. Despite a great deal of research on the aetiology of pressure sores, their origins are still not fully understood. This article discusses the physiology of the skin and the aetiology of pressure sores. Influences on pressure sore development are multifactorial and tend to be divided into three main categories: extrinsic (e.g. environmental pressure, shear and friction), intrinsic (e.g. general health, age, mobility, body weight, incontinence and nutrition), and external factors (e.g. long trolley waits in accident and emergency departments or before admission following a long period collapsed on the floor, hard chairs, and immobilization with traction).