Why is the heel particularly vulnerable to pressure ulcers?

Heel skin microclimate control: Secondary analysis of a self-controlled randomized clinical trial

OBJECTIVE

this study was undertaken to evaluate the efficacy of multilayer polyurethane foam with silicone (MPF) compared to transparent polyurethane film (TPF) dressings in the control of heel skin microclimate (temperature and moisture) of hospitalized patients undergoing elective surgeries.

METHOD

the study took of a secondary analysis of a randomized self-controlled trial, involving patients undergoing elective surgical procedure of cardiac and gastrointestinal specialties in a university hospital in southern Brazil, from March 2019 to February 2020. Patients served as their own control, with their heels randomly allocated to either TPF (control) or MPF (intervention). Skin temperature was measured using a digital infrared thermometer; and moisture determined through capacitance, at the beginning and end of surgery. The study was registered in the Brazilian Registry of Clinical Trials: RBR-5GKNG5.

RESULTS

significant difference in the microclimate variables were observed when the groups (intervention and control) and the timepoint of measurement (beginning and end of surgery) were compared. When assessing temperature, an increase (+3.3 °C) was observed with TPF and a decrease (-7.4 °C) was recorded with MPF. Regarding skin moisture, an increase in moisture (+14.6 AU) was recorded with TPF and a slight decrease (-0.3 AU) with MPF.

CONCLUSIONS

The findings of this study suggest that MPF is more effective than TPF in controlling skin microclimate (temperature and moisture) in heels skin of hospitalized patients undergoing elective surgeries. However, this control should be better investigated in other studies.

The frictional energy absorber effectiveness and its impact on the pressure ulcer prevention performance of multilayer dressings

Pressure ulcers including heel ulcers remain a global healthcare concern. This study comprehensively evaluates the biomechanical effectiveness of the market-popular ALLEVYN® LIFE multilayer dressing in preventing heel ulcers. It focuses on the contribution of the frictional sliding occurring between the non-bonded, fully independent layers of this dressing type when the dressing is protecting the body from friction and shear. The layer-on-layer sliding phenomenon, which this dressing design enables, named here the frictional energy absorber effectiveness (FEAE), absorbs approximately 30%-45% of the mechanical energy resulting from the foot weight, friction and shear acting to distort soft tissues in a supine position, thereby reducing the risk of heel ulcers. Introducing the novel theoretical FEAE formulation, new laboratory methods to quantify the FEAE and a review of relevant clinical studies, this research underlines the importance of the FEAE in protecting the heels of at-risk patients. The work builds on a decade of research published by our group in analysing and evaluating dressing designs for pressure ulcer prevention and will be useful for clinicians, manufacturers, regulators and reimbursing bodies in assessing the effectiveness of dressings indicated or considered for prophylactic use.

Advance in topical biomaterials and mechanisms for the intervention of pressure injury

Pressure injuries (PIs) are localized tissue damage resulting from prolonged compression or shear forces on the skin or underlying tissue, or both. Different stages of PIs share common features include intense oxidative stress, abnormal inflammatory response, cell death, and subdued tissue remodeling. Despite various clinical interventions, stage 1 or stage 2 PIs are hard to monitor for the changes of skin or identify from other disease, whereas stage 3 or stage 4 PIs are challenging to heal, painful, expensive to manage, and have a negative impact on quality of life. Here, we review the underlying pathogenesis and the current advances of biochemicals in PIs. We first discuss the crucial events involved in the pathogenesis of PIs and key biochemical pathways lead to wound delay. Then, we examine the recent progress of biomaterials-assisted wound prevention and healing and their prospects.

Pressure ulcer prevention, patient positioning and protective equipment

Pressure ulcer (PU) prevention is a high priority for health professionals in all settings. While PU incidence is expected to rise given the ageing population in the UK and Europe, PUs can occur in people of any age. It is therefore imperative that all practitioners know about the causes and consequences of PUs and be aware of up-to-date guidance on the prevention and management in patients who have developed a PU or who are at risk of developing a PU. Health professionals should also be aware of preventive equipment highlighted in national and local guidance, prevention strategies and protocols. This article discusses these issues and the Devon (Cardinal Health) prevention and repositioning product range.

MR-compatible loading device for assessment of heel pad internal tissue displacements under shearing load

In the last decade, the role of shearing loads has been increasingly suspected to play a determinant impact in the formation of deep pressure ulcers. In vivo observations of such deformations are complex to obtain. Previous studies only provide global measurements of such deformations without getting the quantitative values of the loads that generate these deformations. To study the role that shearing loads have in the etiology of heel pressure ulcers, an MR-compatible device for the application of shearing and normal loads was designed. Magnetic resonance imaging is a key feature that allows to monitor deformations of soft tissues after loading in a non-invasive way. Measuring applied forces in an MR-environment is challenging due to the impossibility to use magnetic materials. In our device, forces are applied through the compression of springs made of polylactide. Shearing and normal loads were applied on the plantar skin of the human heel through a flat plate while acquiring MR images. The device materials did not introduce any imaging artifact and allowed for high quality MR deformation measurements of the internal components of the heel. The obtained subject-specific results are an original data set that can be used in validations for Finite Element analysis and therefore contribute to a better understanding of the factors involved in pressure ulcer development.

Simple model of arch support: Relevance to Charcot Neuroarthropathy

BACKGROUND

Charcot neuropathy is a common complication resulting from poorly controlled diabetes and peripheral neuropathy leading to the collapse, and ultimately the breakdown, of the midfoot. Mechanically, it is likely that a compromised arch support in this, or any other patient group that experiences foot flattening, would be associated with slippage at the distal and proximal interface regions of the plantar surface of the foot and the adjacent support surface. This slippage, although difficult to quantify with standard motion capture systems used in a gait laboratory, could potentially be assessed with systems for monitoring interface shear stresses. However, before investing in such systems, a correlation between arch flattening and interface shear stresses needs to be verified.

METHODS

For this purpose, a sagittal plane model of a foot was developed using a multi-body dynamics package (MSC Adams). This model mimicked a subject swaying back and forth, and was constructed to show the dependence of interface stresses on altered arch support.

FINDINGS

The model's predictions matched typical FootSTEPS data: lengthening of the arch of 1-2 mm, sway oscillations of 0.22-0.33 s and frictional force differences (calcaneus relative to forefoot) of 60 N. Of clinical relevance, when the stiffness of the plantar spring (representing aponeurosis and intrinsic muscles) was reduced by 10%, the frictional force difference increased by about 6.5%.

INTERPRETATION

The clinical implications of this study are that, while arch lengthening of less than 2 mm might be difficult to measure reliably in a gait lab, using shear sensors under the forefoot and hindfoot should allow arch support to be assessed in a repeatable manner.

Comparing the physical performance of liquid barrier films

Background

Barrier films have been used for many years to protect skin from the damaging effects of excessive moisture and mechanical injury. The performance characteristics important for these protective effects are mainly product durability and its ability to reduce the force of adhesive removal. Additionally, the moisture vapor transmission rate through the film needs to be high enough that maceration is prevented. The current study was undertaken to investigate various physical performance characteristics of six commercially available barrier films.

Materials and methods

Several bench tests were used to simulate performance features of the barriers on skin including barrier durability, breathability (moisture vapor permeability), and the effect on adhesive dressing force of removal.

Results

Results indicated that barrier films did not perform equivalently. However, Cavilon™ No Sting Barrier Film (NSB) was shown to have significantly greater durability in the barrier integrity test than all other barriers tested and was tied for highest breathability and highest reduction in peel force from steel. No other tested barrier film performed as consistently across the different tests.

Conclusion

These results may provide mechanistic understanding of how barriers such as NSB may clinically assist with the prevention of adhesive‐ and moisture‐related skin damage.

Prevention of pressure injury in the operating room: Heels operating room pressure injury trial

The objective was to evaluate the efficacy of multi‐layered silicone foam (intervention) compared with transparent polyurethane film (control) in preventing heel pressure injuries caused by surgical positioning of individuals undergoing elective surgery. It was designed an intra‐patient, open, parallel, randomised controlled trial was conducted in a university hospital in southern Brazil, from March 2019 to February 2020, with patients undergoing elective surgeries of cardiac and gastrointestinal specialties. The patients who met the selection criteria constituted, simultaneously, a single group receiving the intervention and active control, through paired analysis of the cutaneous sites (right heel and left heel). The outcome was the occurrence of PI, within the follow‐up period was 72 hours. Brazilian Registry of Clinical Trials: RBR‐5GKNG5. There was analysis of 135 patients/270 heels, with an overall incidence of 36.7%. The pressure injury incidence was significantly lower in the intervention group (26.7%), compared with the control group (P = .001); relative risk of 0.57. In the intervention group, the estimated pressure injury‐free time (survival) was 57.5 hours and in the control group, 43.9 hours. It was concluded that Multi‐layered silicone foam (intervention) is more efficacious than transparent polyurethane film (control) in the prevention of pressure injuries caused by surgical positioning of individuals undergoing elective surgery.

The sorptivity and durability of gelling fibre dressings tested in a simulated sacral pressure ulcer system

Wound‐dressing performances are affected by exudate viscosity, resistance to flow because of gravity, and bodyweight loads, the level of which is related to the body position. Here, we focussed on two dressing properties: (a) Sorptivity—the ability of dressings to transfer exudate away from the wound bed by capillary action—and (b) Durability—the capacity of dressings to maintain their integrity over time and during their removal. Both properties are critically important for avoiding further tissue damage but require the development of new laboratory tests for their measurement. A computer‐controlled phantom of an exuding sacral pressure ulcer has therefore been developed and used to compare the performances of Exufiber (Mölnlycke Health Care) vs an alternative market‐leading dressing. Sorptivity was determined using weight tests, and durability was measured through tensile tests of the used dressings. For a supine configuration, the Exufiber dressing demonstrated ~three times higher sorptivity and better durability, withstanding ~five times greater strain energy than the other product before failure occurred. This work paves the way for quantitative, standardised testing of dressings in all aspects of exudate management. The reported tests are further suitable for testing dressing combinations or how dressings interact with negative pressure wound therapy.

Risk factors for developing heel ulcers for bedridden patients: A finite element study

BACKGROUND

The heel is one of the most common sites of pressure ulcers and the anatomical location with the highest prevalence of deep tissue injury. Several finite element modeling studies investigate heel ulcers for bedridden patients. In the current study we have added the implementation of the calf structure to the current heel models. We tested the effect of foot posture, mattress stiffness, and a lateral calcaneus displacement to the contact pressure and internal maximum shear strain occurring at the heel.

METHODS

A new 3D finite element model is created which includes the heel and calf structure. Sensitivity analyses are performed for the foot orientation relative to the mattress, the Young's modulus of the mattress, and a lateral displacement of the calcaneus relative to the other soft tissues in the heel.

FINDINGS

The models predict that a stiffer mattress results in higher contact pressures and internal maximum shear strains at the heel as well as the calf. An abducted foot posture reduces the internal strains in the heel and a lateral calcaneus displacement increases the internal maximum shear strains. A parameter study with different mattress-skin friction coefficients showed that a coefficient below 0.4 decreases the maximum internal shear strains in all of the used loading conditions.

INTERPRETATION

In clinical practice, it is advised to avoid internal shearing of the calcaneus of patients, and it could be taken into consideration by medical experts and nurses that a more abducted foot position may reduce the strains in the heel.

Finite element analysis reveals an important role for cell morphology in response to mechanical compression

Mechanical loading naturally controls cell phenotype, development, motility and various other biological functions; however, prolonged or substantial loading can cause cell damage and eventual death. Loading-induced mechanobiological and mechanostructural responses of different cell types affect their morphology and the internal architecture and the mechanics of the cellular components. Using single, mesenchymal stem cells, we have developed a cell-specific three-dimensional finite-element model; cell models were developed from phase-contrast microscopy images. This allowed us to evaluate the mechanostructural response of the naturally occurring variety of cell morphologies to increase sustained compressive loading. We focus on the morphology of the cytoplasm and the nucleus, as the main mechanically responsive elements, and evaluate formation of tensional strains and area changes in cells undergoing increasing uniaxial compressions. Here, we study mesenchymal stem cells as a model, due to their important role in tissue engineering and regenerative medicine; the method and findings are, however, applicable to any cell type. We observe variability in the cell responses to compression, which correlate directly with the morphology of the cells. Specifically, in cells with or without elongated protrusions (i.e., lamellipodia) tensional strains were, respectively, distributed mostly in the thin extensions or concentrated around the stiff nucleus. Thus, through cell-specific computational modeling of mechanical loading we have identified an underlying cause for stiffening (by actin recruitment) along the length of lamellipodia as well as a role for cell morphology in inducing cell-to-cell variability in mechanostructural response to loading.

Preventing pressure injuries in the emergency department: Current evidence and practice considerations

The emergency department (ED) is at the front line of hospital pressure injury (PI) prevention, yet ED clinicians must balance many competing clinical priorities in the care of seriously ill patients. This paper presents the current biomechanical and clinical evidence and management considerations to assist EDs to continue to develop and implement evidence-based PI prevention protocols for the high-risk emergency/trauma patient. The prevention of hospital-acquired pressure injuries has received significant focus internationally over many years because of the additional burden that these injuries place on the patient, the additional costs and impact to the efficiency of the hospital, and the potential for litigation. The development of a PI is the result of a complex number of biomechanical, physiological, and environmental interactions. Our understanding of the interaction of these factors has improved significantly over the past 10 years. We have demonstrated that large reductions in PI incidence rates can be achieved in critical care and general hospital wards through the application of advanced evidence-based prevention protocols and believe that further improvement can be achieved through the application of these approaches in the ED.

Dressings and topical agents for preventing pressure ulcers

BACKGROUND

Pressure ulcers, localised injuries to the skin or underlying tissue, or both, occur when people cannot reposition themselves to relieve pressure on bony prominences. These wounds are difficult to heal, painful, expensive to manage and have a negative impact on quality of life. Prevention strategies include nutritional support and pressure redistribution. Dressing and topical agents aimed at prevention are also widely used, however, it remains unclear which, if any, are most effective. This is the first update of this review, which was originally published in 2013.

OBJECTIVES

To evaluate the effects of dressings and topical agents on pressure ulcer prevention, in people of any age, without existing pressure ulcers, but considered to be at risk of developing one, in any healthcare setting.

SEARCH METHODS

In March 2017 we searched the Cochrane Wounds Group Specialised Register, CENTRAL, MEDLINE, MEDLINE (In-Process & Other Non-Indexed Citations), Embase, and EBSCO CINAHL Plus. We searched clinical trials registries for ongoing trials, and bibliographies of relevant publications to identify further eligible trials. There was no restriction on language, date of trial or setting. In May 2018 we updated this search; as a result several trials are awaiting classification.

SELECTION CRITERIA

We included randomised controlled trials that enrolled people at risk of pressure ulcers.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed risk of bias and extracted data.

MAIN RESULTS

The original search identified nine trials; the updated searches identified a further nine trials meeting our inclusion criteria. Of the 18 trials (3629 participants), nine involved dressings; eight involved topical agents; and one included dressings and topical agents. All trials reported the primary outcome of pressure ulcer incidence.Topical agentsThere were five trials comparing fatty acid interventions to different treatments. Two trials compared fatty acid to olive oil. Pooled evidence shows that there is no clear difference in pressure ulcer incidence between groups, fatty acid versus olive oil (2 trials, n=1060; RR 1.28, 95% CI 0.76 to 2.17; low-certainty evidence, downgraded for very serious imprecision; or fatty acid versus standard care (2 trials, n=187; RR 0.70, 95% CI 0.41 to 1.18; low-certainty evidence, downgraded for serious risk of bias and serious imprecision). Trials reported that pressure ulcer incidence was lower with fatty acid-containing-treatment compared with a control compound of trisostearin and perfume (1 trial, n=331; RR 0.42, 95% CI 0.22 to 0.80; low-certainty evidence, downgraded for serious risk of bias and serious imprecision). Pooled evidence shows that there is no clear difference in incidence of adverse events between fatty acids and olive oil (1 trial, n=831; RR 2.22 95% CI 0.20 to 24.37; low-certainty evidence, downgraded for very serious imprecision).Four trials compared further different topical agents with placebo. Dimethyl sulfoxide (DMSO) cream may increase the risk of pressure ulcer incidence compared with placebo (1 trial, n=61; RR 1.99, 95% CI 1.10 to 3.57; low-certainty evidence; downgraded for serious risk of bias and serious imprecision). The other three trials reported no clear difference in pressure ulcer incidence between active topical agents and control/placebo; active lotion (1 trial, n=167; RR 0.73, 95% CI 0.45 to 1.19), Conotrane (1 trial, n=258; RR 0.74, 95% CI 0.52 to 1.07), Prevasore (1 trial, n=120; RR 0.33, 95% CI 0.04 to 3.11) (very low-certainty evidence, downgraded for very serious risk of bias and very serious imprecision). There was limited evidence from one trial to determine whether the application of a topical agent may delay or prevent the development of a pressure ulcer (Dermalex^TM 9.8 days vs placebo 8.7 days). Further, two out of 76 reactions occurred in the Dermalex^TM group compared with none out of 91 in the placebo group (RR 6.14, 95% CI 0.29 to 129.89; very low-certainty evidence; downgraded for very serious risk of bias and very serious imprecision).DressingsSix trials (n = 1247) compared a silicone dressing with no dressing. Silicone dressings may reduce pressure ulcer incidence (any stage) (RR 0.25, 95% CI 0.16 to 0.41; low-certainty evidence; downgraded for very serious risk of bias). In the one trial (n=77) we rated as being at low risk of bias, there was no clear difference in pressure ulcer incidence between silicone dressing and placebo-treated groups (RR 1.95, 95% CI 0.18 to 20.61; low-certainty evidence, downgraded for very serious imprecision).One trial (n=74) reported no clear difference in pressure ulcer incidence when a thin polyurethane dressing was compared with no dressing (RR 1.31, 95% CI 0.83 to 2.07). In the same trial pressure ulcer incidence was reported to be higher in an adhesive foam dressing compared with no dressing (RR 1.65, 95% CI 1.10 to 2.48). We rated evidence from this trial as very low certainty (downgraded for very serious risk of bias and serious imprecision).Four trials compared other dressings with different controls. Trials reported that there was no clear difference in pressure ulcer incidence between the following comparisons: polyurethane film and hydrocolloid dressing (n=160, RR 0.58, 95% CI 0.24 to 1.41); Kang' huier versus routine care n=100; RR 0.42, 95% CI 0.08 to 2.05); 'pressure ulcer preventive dressing' (PPD) versus no dressing (n=74; RR 0.18, 95% CI 0.04 to 0.76) We rated the evidence as very low certainty (downgraded for very serious risk of bias and serious or very serious imprecision).

AUTHORS' CONCLUSIONS

Most of the trials exploring the impact of topical applications on pressure ulcer incidence showed no clear benefit or harm. Use of fatty acid versus a control compound (a cream that does not include fatty acid) may reduce the incidence of pressure ulcers. Silicone dressings may reduce pressure ulcer incidence (any stage). However the low level of evidence certainty means that additional research is required to confirm these results.

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

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

Mitigating the damaging effects of tissue distortions by using a low-friction heel protector

This article reports the finding of a small non-controlled evaluation over a 2-week period in three different care settings: a residential care home, an acute stroke unit and a community intermediate care hospital. At initial recruitment 30 patients were identified by clinical assessment as being at high risk of developing a heel pressure ulcer. Further inclusion criteria were identifying heels that had signs of pressure damage occurring, blanching and non-blanching erythema, blistering and category 2 ulceration. In all, 15 patients fully completed the evaluation over a 14-day period. The mean age was 86 years. The low-friction bootee was worn constantly while in bed and seated in chairs, only being removed for heel checks and hygiene care. No patients were independently mobile during the evaluation; products were not worn to walk in due to a risk of falling-patients in the community hospital who had to mobilise for rehabilitation removed the bootees for this activity. All had pressure mapping and ultrasound of pedal pulses prior and after evaluation by the tissue viability specialist nurse. Results of pressure mapping showed a reduction of peak heel pressures on application of the bootees and a final review of reduction in visual signs of heel damage, reduced pain, increased comfort and ease of use. These results indicate that a standardised care pathway approach to heel protection using low-friction heel bootees is effective in all care settings for the reduction and prevention of heel pressure damage.

A randomised controlled trial of the clinical effectiveness of multi-layer silicone foam dressings for the prevention of pressure injuries in high-risk aged care residents: The Border III Trial

Pressure injuries are prevalent in highly dependent aged care residents. This study investigated the clinical effectiveness of the application of the Mepilex Border Sacrum and Mepilex Heel dressings to prevent the development of facility-acquired pressure injuries. A total of 288 recently admitted residents were enrolled from 40 Australian nursing homes into a randomised controlled trial. Residents randomised to standard care (n = 150) received pressure injury prevention as recommended by international guidelines. Residents randomised to the intervention (n = 138) received standard pressure injury prevention care and had dressings applied to their sacrum and heels. Participants were comparable on demographic and physiological parameters. More residents in the control group developed pressure injuries than in the intervention group (16 vs 3, P = 0.004), and they developed more pressure injuries in total than residents in the intervention group. The results represent a relative risk reduction of 80% for residents treated with the dressings and for every 12 patients that we treated we prevented one pressure injury. Based on our findings, we conclude that the use of the Mölnlycke Mepilex Border Sacrum and Mepilex Heel dressings confers a significant additional protective benefit to nursing home residents with a high risk of developing a facility-acquired pressure injury.