Foam Mattress Research Articles

Effect of circumferential rounding of the bottom disc on the pressure distribution at the interface of the measurement device and urethane foam mattress

Effect of circumferential rounding of the bottom disc on the pressure distribution at the interface of the measurement device and urethane foam mattress

Pressure RElieving Support SUrfaces: a Randomised Evaluation 2 (PRESSURE 2): study protocol for a randomised controlled trial.

BackgroundPressure ulcers represent a major burden to patients, carers and the healthcare system, affecting approximately 1 in 17 hospital and 1 in 20 community patients. They impact greatly on an individual’s functional status and health-related quality of life. The mainstay of pressure ulcer prevention practice is the provision of pressure redistribution support surfaces and patient repositioning. The aim of the PRESSURE 2 study is to compare the two main mattress types utilised within the NHS: high-specification foam and alternating pressure mattresses, in the prevention of pressure ulcers.Methods/DesignPRESSURE 2 is a multicentre, open-label, randomised, double triangular, group sequential, parallel group trial. A maximum of 2954 ‘high-risk’ patients with evidence of acute illness will be randomised on a 1:1 basis to receive either a high-specification foam mattress or alternating-pressure mattress in conjunction with an electric profiling bed frame. The primary objective of the trial is to compare mattresses in terms of the time to developing a new Category 2 or above pressure ulcer by 30 days post end of treatment phase. Secondary endpoints include time to developing new Category 1 and 3 or above pressure ulcers, time to healing of pre-existing Category 2 pressure ulcers, health-related quality of life, cost-effectiveness, incidence of mattress change and safety. Validation objectives are to determine the responsiveness of the Pressure Ulcer Quality of Life-Prevention instrument and the feasibility of having a blinded endpoint assessment using photography. The trial will have a maximum of three planned analyses with unequally spaced reviews at event-driven coherent cut-points. The futility boundaries are constructed as non-binding to allow a decision for stopping early to be overruled by the Data Monitoring and Ethics Committee.DiscussionThe double triangular, group sequential design of the PRESSURE 2 trial will provide an efficient design through the possibility of early stopping for demonstrating either superiority, inferiority of mattresses or futility of the trial. The trial optimises the potential for producing robust clinical evidence on the effectiveness of two commonly used mattresses in clinical practice earlier than in a conventional design.Trial registration ISRCTN01151335. Registered on 14 May 2013. Protocol version: 5.0, dated 25 September 2015Trial sponsor: Clare Skinner, Faculty Head of Research Support, University of Leeds, Leeds, LS2 9JT; 0113 343 4897; C.E.Skinner@leeds.ac.uk.

The effect of walking on inclined surfaces (uphill and downhill) on gait parameters of healthy subjects using self-paced treadmill in virtual environments

This research presents the finite element modeling (FEM) of human-specific computed tomography (CT) data to study the effect of bone prominences on contact stress in the shoulder for prevention of pressure ulcers. The 3D geometry of scapula, skin, and surrounding soft tissues in the shoulder was reconstructed based on the anonymous CT data of a human subject in a prone posture (without loading on the shoulder) for FEM analysis of the contact stress. FEM analysis results show that the maximum stress is located at the prominence of the scapula with sharp bone geometry. This demonstrates that stress concentration at the bone prominence is a significant factor to cause the high contact stress, which is a source for pressure ulcers. For experimental validation, a physical shoulder model manufactured by 3D printing of the bone geometry and the mold for molding of tissue-mimicking silicone was developed. Compression tests of the mattress foam and silicone were conducted to find the nonlinear stress–strain relations as inputs for FEM. Experiments of compressing the shoulder model against the foam were carried out. Three flexible force sensors were embedded inside the model to measure the contact forces and compared to the FEM predictions. Results show that the FEM predicted forces match well with the experimental measurements and demonstrate that FEM can accurately predict the stress distributions in the shoulder to study the effect of bone geometry on the inception of pressure ulcers.

The effect of human-mattress interface's temperature on perceived thermal comfort

In recent years, methods that allow for an objective evaluation of perceived comfort, in terms of postural, physiological, cognitive and environmental comfort, have received a great deal of attention from researchers. This paper focuses on one of the factors that influences physiological comfort perception: the temperature difference between users and the objects with which they interact. The first aim is to create a measuring system that does not affect the perceived comfort during the temperatures' acquisition. The main aim is to evaluate how the temperature at the human-mattress interface can affect the level of perceived comfort. A foam mattress has been used for testing in order to take into account the entire back part of the human body. The temperature at the interface was registered by fourteen 100 Ohm Platinum RTDs (Resistance Temperature Detectors) placed on the mattress under the trunk, the shoulders, the buttocks, the legs, the thighs, the arms and the forearms of the test subject. 29 subjects participated in a comfort test in a humidity controlled environment. The test protocol involved: dress-code, anthropometric-based positioning on mattress, environment temperature measuring and an acclimatization time before the test. At the end of each test, each of the test subject's thermal sensations and the level of comfort perception were evaluated using the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) scale. The data analyses concerned, in the first instance, correlations between the temperature at the interface and comfort levels of the different parts of the body. Then the same analyses were performed independently of the body parts being considered. The results demonstrated that there was no strong correlation among the studied variables and that the total increase of temperature at interface is associated with a reduction in comfort.

Finite element modeling for predicting the contact pressure between a foam mattress and the human body in a supine position

In this paper, we generated finite element (FE) models to predict the contact pressure between a foam mattress and the human body in a supine position. Twenty-year-old males were used for three-dimensional scanning to produce the FE human models, which was composed of skin and muscle tissue. A linear elastic isotropic material model was used for the skin, and the Mooney–Rivlin model was used for the muscle tissue because it can effectively represent the nonlinear behavior of muscle. The contact pressure between the human model and the mattress was predicted by numerical simulation. The human models were validated by comparing the body pressure distribution obtained from the same human subject when he was lying on two different mattress types. The experimental results showed that the slope of the lower part of the mattress caused a decrease in the contact pressure at the heels, and the effect of bone structure was most pronounced in the scapula. After inserting a simple structure to function as the scapula, the contact pressure predicted by the FE human models was consistent with the experimental body pressure distribution for all body parts. These results suggest that the models proposed in this paper will be useful to researchers and designers of products related to the prevention of pressure ulcers.

Dietary and Household Sources of Prenatal Exposure to Polybrominated Diphenyl Ethers (PBDEs) in the INMA Birth Cohort (Spain).

This study looked at predictors of exposure to polybrominated diphenyl ethers (PBDEs) with a focus on dietary and household-level factors. Concentrations of BDE-47, -99, -153, and -209 and their sum (∑PBDEs) were measured in cord serum. Spanish women (n = 541) completed two semiquantitative food frequency questionnaires during the first and third trimesters of pregnancy. The daily mean intake (grams) of eggs, dairy products, meat, cereals and pasta, vegetables and pulses, fruits, shellfish and cephalopods, and fish, and the weekly mean intake (servings) of lean, large oily, other oily, and other fish from both questionnaires were averaged. Information on house size, curtains and carpets at home, mattress type, housekeeping frequency, and television use was also collected later in gestation. Multivariate censored regression was used to assess the association between PBDE concentration (log2 transformed) and potential predictors. BDE-47, -99, -209 and ∑PBDE concentrations increased by 13.6%(95% CI:0.0, 29.0%), 21.1%(2.3, 43.5%), 21.7%(0.4, 47.5%) and 11.5%(2.2, 21.7%), respectively, per interquartile range increment in daily intake of shellfish and cephalopods. Fish intake was associated with BDE-99 (20.8%[1.7, 43.4%]). When fish was disaggregated by types, BDE-99 and ∑PBDEs increased by 13.8%(4.0, 24.7%) and 5.7%(0.8, 10.8%), respectively, per 1-serving/week increment in large oily fish intake. BDE-153 was associated with higher housekeeping frequency (35.9%[0.4, 83.9%]) and BDE-209 with foam mattress use (48.9%[5.8, 109.7%]). In conclusion, seafood consumption, higher housekeeping frequency, and foam mattress were associated with prenatal PBDE exposure.

Effect of Urethane Foam Cushioning on Structure-Borne Sound Transfer by a Slab with Panel Flooring

Abstract Urethane foam mattresses are commonly used as cushioning when placing panel flooring on the floor slab of a building. Urethane foam consists of elastic fibres with pores. Both elements can affect the performance of the insulation against impact sounds. However, these effects have not yet been detailed, and they may change if the material properties or constitution of the fibres and pores in the cushioning change. In this paper, we propose an analytical model for use in evaluating the performance of insulation against floor impact sound. This model was used to examine the contribution of the pores versus the elastic fibres to wave transmissions from the flooring surface to the slab. The results reveal that the constitution of the foam (either open or closed cells of pores) and the thickness and hardness of the cushion layer strongly affect the sound insulation performance of the floor.

Crib Mattress Investigation: A quality improvement study to assess mattress cover permeability and bacterial growth in crib mattresses

Any opening in a medical bed mattress cover may allow bodily fluids to enter the mattress, leading to contamination and potential nosocomial infection. This study's purpose was to assess permeability of crib mattress covers and measure bacterial growth within and on crib mattress surfaces. Mattresses were selected randomly from hospital inventory. Bonney's blue dye was applied over mattress covers to assess permeability. Mattress cover surface swabs were acquired from standardized locations. Samples of mattress foam were acquired under sterile conditions. All samples were collected with the Eswab and eMRSA systems (Copan Diagnostics Inc, Brescia, Italy). Total aerobic bacteria count and colony types were assessed. Results are presented as mean ± standard error of the mean, independent t tests and analysis of variance were used to analyze data, and significance was achieved with P < .05. All mattresses (n = 7) had Bonney's blue dye visible on underlying mattress foam. There were 77 samples and 44 had bacterial growth. Total bacterial count ranged from 0.2-11.6 CFU/cm(2) with mean of 1.7 ± 0.38 CFU/cm(2). There was no relative differences between mattress sample location and colony type. All samples were negative for Staphylococcus aureus, including methicillin-resistant S aureus. Any crack in a mattress cover renders it permeable to fluid entering the mattress. Bacterial growth was present on mattress covers and within mattress foam. Mattresses support microbial viability from which nosocomial infection may occur.

Performance of different support surfaces during experimental resuscitation (CPR).

The relationship between the efficacy of resuscitation and the mattresses and backboards used in acute care units, has been studied previously. However, few reports focus on the relative efficacy of resuscitation when using mattresses with different modes of function. This study examines the performance of different support surfaces during experimental cardiopulmonary resuscitation (CPR). The surfaces included a hard surface, a higher specification foam mattress, a dynamic, alternating pressure mattress, and a dynamic, reactive minimum pressure air mattress system. A pressure sensitive mat was placed between the mattresses and each surface and the efficacy of resuscitation measured using differences in compression frequency, compression depth and hands-on time. Our results suggest that the efficacy of resuscitation is dependent on the mode of action of the mattress, while adequate compression frequency and depth do not have a significant effect. In the open system alternating mattress, deflation of the mattress using the CPR function improved the stability of the resuscitation in our study, especially in situations where the height of the air mattress is greater than 20–25 centimeters. Using our experimental system, resuscitation on a closed air system mattress optimally combined stability and effort, while the CPR function converts the air system of the mattress to open, which impairs its functionality during resuscitation. These results indicate that resuscitation is dependent of the mode of action of the mattress and whether the mattress-specific CPR function was used or not. However, the interactions are complex and are dependent on the interaction between the body and the mattress, i.e. its immersion and envelopment properties. Furthermore, this study casts doubt on the necessity of the CPR function in air mattresses.

The Health Centre Community.

The greatest burden of malaria is borne by the children of rural sub-Saharan Africa. Each year nearly 90% of all malaria-related deaths occur in these remote areas, far from lifesaving medical care. In the Bugoye sub-county of rural Western Uganda, most families subsist on small plots of staple crops carved into the hillsides. Lacking transportation, worried parents carry their sick children down the narrow mountain paths to the health centre in search of care (Figure 1). The Level III Health Centre in Bugoye is the only facility in the sub-county—an area spanning more than 40 villages and nearly 60 km—equipped to treat cases of severe malaria. During the high season, hundreds of malaria-stricken children come to the health centre each week for diagnosis and treatment (Figure 2). Like many public health facilities in rural sub-Saharan Africa, the Bugoye Health Centre faces many challenges, including drug shortages, unreliable electrical power and inadequate staffing. The health centre is not shiny or new. There are no private rooms. The unfinished cement floors are cracked, the paint is peeling, the thin foam mattresses are worn and tattered and most of the equipment is decades old (Figure 3). What Bugoye does have, however, is a vibrant sense of community. In many ways, the health centre has the atmosphere of a bustling village unto itself. It is the heart of the sub-county. Entire families inhabit the wards, providing food, linen and clothing for their sick loved ones (Figures 4 and 5).The bright colours of children in church clothes dot the yard and groups of women gather behind the clinic, preparing meals over open fires (Figure 6). Village officials, health centre staff and local tradesmen sit on the benches at the front to wave to friends, chat about

力学試験と超弾性モデルの適用によるウレタンフォームマットレスの骨突起部圧分散メカニズムの解明

力学試験と超弾性モデルの適用によるウレタンフォームマットレスの骨突起部圧分散メカニズムの解明

Synthetic Logs for Controlled Culture of Epixylic Bryophytes: Log Physical Properties, Surface Moisture, andDicranum flagellareGrowth

Abstract. Experimental studies of epixylic bryophytes require stable, biologically inactive substrata with physical properties that mimic those of coarse decayed wood. In two preliminary tests, we compared three synthetic logs (made from upholstery wadding, mattress foam, and floral foam) to decayed natural logs, in terms of their physical properties, moisture transmission, and ability to support growth of Dicranum flagellare in the laboratory. We also tested the effects of clumped vs. smeared propagule application on growth response. Vegetative moss propagules (flagellae and dried gametophore fragments) were applied as clumps or smears with nutrient agar gel, and evaluated as to horizontal expansion, vertical growth and dry weight of new growth over 6 months. Synthetic logs had higher porosity and lower density than natural logs, but showed similar moisture transmission capabilities to each other and to natural logs when moisture was supplied from the base. Nevertheless, surficial water potentials were c...

Influence of biological fluids in bacterial viability on different hospital surfaces and fomites

The hospital environment is susceptible to bacterial contamination along with survival in fomites and surfaces, allowing dissemination of potential pathogenic strains. The present research aimed to evaluate the influence of biological fluids in bacterial viability on fomites and surfaces commonly present in nosocomial environment. Four different fomites and surfaces (ceramic floor, cotton fabric fragments and synthetic fibers, and eggcrate foam mattress) were contaminated with potential pathogens (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Klebsiella pneumoniae), then submitted to influence of biological fluids (blood, urine, artificial saliva). The viability of strains was evaluated at 24 hours after contamination and then in intervals of 7days, by the colony-forming unit count technique. S aureus presented viability (>70days) in all conditions tested, E faecalis and K pneumoniae had decreased viability over time, and E coli did not exhibit a growth relationship with surfaces or fluids. Persistence and adaptability capacity of potential pathogens in fomites and surfaces exposed to the patient are important for guidance, planning, and outlining of protocols for microorganism dissemination control and prevention in the health care environment.

Development and application of special position mattress for endoscopic retrograde cholangiopancreatography

Objective To design a kind of special support mattress for the endoscopic retrograde cholangiopancreatography (ERCP), and to improve the comfort of the patients during the procedure, and evaluate the efficacy and safety during clinical application. Methods By 3D modeling, we designed a special memory foam mattress for ERCP. From January 2014 to September 2014, 424 patients who underwent ERCP treatment without general anesthesia and could take semi-prone position, were divided into special mattress group (210 cases) and ordinary mattress group (214 cases) according to the random number table method. The satisfaction of the patients and the operators of the two groups were evaluated and compared. Results The operation times of the two groups were (32.9±18.5) min and (33.2±20.1) min, respectively, and there was no significant difference between the two groups (P>0.05). The overall satisfaction ratings of the patients in the two groups were (7.9±1.6) points and (6.3±1.3) points, respectively (P 0.05). No mattress related complications were found. Conclusions The special memory foam mattress for ERCP can alleviate the discomfort and improve the tolerance during the procedure. Therefore, it is worth promoting the application. Key words: Cholangiopancreatography, endoscopic retrograde; Nursing care; Special position mattress

Support surfaces for pressure ulcer prevention.

Pressure ulcers (i.e. bedsores, pressure sores, pressure injuries, decubitus ulcers) are areas of localised damage to the skin and underlying tissue.They are common in the elderly and immobile, and costly in financial and human terms. Pressure-relieving support surfaces (i.e. beds, mattresses, seat cushions etc) are used to help prevent ulcer development. This systematic review seeks to establish:(1) the extent to which pressure-relieving support surfaces reduce the incidence of pressure ulcers compared with standard support surfaces, and,(2) their comparative effectiveness in ulcer prevention. In April 2015, for this fourth update we searched The Cochrane Wounds Group Specialised Register (searched 15 April 2015) which includes the results of regular searches of MEDLINE, EMBASE and CINAHL and The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2015, Issue 3). Randomised controlled trials (RCTs) and quasi-randomised trials, published or unpublished, that assessed the effects of any support surface for prevention of pressure ulcers, in any patient group or setting which measured pressure ulcer incidence. Trials reporting only proxy outcomes (e.g. interface pressure) were excluded. Two review authors independently selected trials. Data were extracted by one review author and checked by another.Where appropriate, estimates from similar trials were pooled for meta-analysis. For this fourth update six new trials were included, bringing the total of included trials to 59.Foam alternatives to standard hospital foam mattresses reduce the incidence of pressure ulcers in people at risk (RR 0.40 95% CI 0.21 to 0.74).The relative merits of alternating- and constant low-pressure devices are unclear. One high-quality trial suggested that alternating-pressure mattresses may be more cost effective than alternating-pressure overlays in a UK context.Pressure-relieving overlays on the operating table reduce postoperative pressure ulcer incidence, although two trials indicated that foam overlays caused adverse skin changes. Meta-analysis of three trials suggest that Australian standard medical sheepskins prevent pressure ulcers (RR 0.56 95% CI 0.32 to 0.97). People at high risk of developing pressure ulcers should use higher-specification foam mattresses rather than standard hospital foam mattresses. The relative merits of higher-specification constant low-pressure and alternating-pressure support surfaces for preventing pressure ulcers are unclear, but alternating-pressure mattresses may be more cost effective than alternating-pressure overlays in a UK context. Medical grade sheepskins are associated with a decrease in pressure ulcer development. Organisations might consider the use of some forms of pressure relief for high risk patients in the operating theatre.

Dietary And Household Sources Of Exposure To Polybrominated Flame Retardants

Introduction: Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants and humans are exposed to them in their everyday life. The aim was to evaluate household and dietary determinants of PBDE exposure in newborns from a Spanish cohort (n=541). Methods: Umbilical cord concentrations of BDE-47, -99, -153, and -209 and their sum (∑PBDEs) were determined. At 10-13 and 28-32 gestational weeks, women completed 2 semiquantitative food frequency questionnaires. The average daily intake (grams) of eggs, dairy products, meat, fish, shellfish, cereal and pasta, vegetables and pulses, and fruits was considered. Intake of fish types (lean, large oily and small oily fish) was expressed in weekly servings. Women also completed 2 questionnaires on anthropometric, sociodemographic and lifestyle information, including questions on activities that may increase PBDE exposure: frequent electromagnetic field exposure at work (yes, no), house size (m2), curtains at home (yes, no), carpets at home (yes, no), type of mattress (innerspring, foam), housekeeping frequency (≤ or =1 times/wk), and television use (hrs/wk). Multivariate Tobit regression was used to assess the association between log2-transformed PBDEs and sources of exposure. Results: BDE-99, -209 and ∑PBDEs concentrations increased by 20.8% (95% CI: 0.9, 44.6), 24.3% (1.6, 52.2) and 12.0% (2.1, 22.8), respectively, per interquartile range increment in shellfish intake. Fish intake was associated with BDE-99 (21.1% [1.8, 44.1]) and marginally (p≤0.1) with BDE-47 and ∑PBDEs. When fish was disaggregated by types, BDE-99 and ∑PBDEs increased by 13.8% (4.0, 24.7) and 5.7% (0.8, 10.8), respectively, per 1 serving/wk increment in large oily fish intake. BDE-153 was associated with higher frequency of housekeeping (35.9% [0.4, 83.9]) and BDE-209 with foam mattresses (48.9% [5.8, 109.7]). Conclusions: Shellfish and large oily fish intake may be major contributors to PBDE body burden of newborns in Spain.

Analysis of the Pressure Distribution Qualities of a Silicone Border Foam Dressing.

To determine whether application of a silicone foam dressing is associated with decreased interface pressures when applied to the heel. Prospective, within-subjects design. The study was conducted in a community-based hospital using a convenience sample of 50 healthy volunteers with a mean age of 39.6 years and mean body mass index of 26.6; 70% were female. Application of the silicone border foam dressing was randomized between the left and right heels. Participants were asked to lie down in the supine position on a viscoelastic foam mattress. Interface pressure measurements were captured using a pressure mapping system; measurements were taken once with the dressing applied to the heel (intervention map) and once without (control map). Data were captured after a 4-minute time period allowing stabilization. Analysis was based on mean interface pressure; data points were collected for both heels in each of the 2 frames, yielding 4 observations per subject. Application of the dressing was associated with a significant decrease in average pressure measurements as compared to the heel with no dressing applied (P < .001). Application of the dressing did not impact pressure readings for the heel to which no dressing was applied (P = .53), and application of the dressing to either the left or right heel did not impact pressure readings (ie, the random effect was insignificant; P = .9). Application of a silicone border foam dressing is associated with significant reduction in interface pressure and may be considered as part of a pressure ulcer prevention program.

Seeking effective interventions to treat complex wounds: an overview of systematic reviews.

BackgroundNumerous, often multi-faceted regimens are available for treating complex wounds, yet the evidence of these interventions is recondite across the literature. We aimed to identify effective interventions to treat complex wounds through an overview of systematic reviews.MethodsMEDLINE (OVID interface, 1946 until October 26, 2012), EMBASE (OVID interface, 1947 until October 26, 2012), and the Cochrane Database of Systematic Reviews (Issue 10 of 12, 2012) were searched on October 26, 2012. Systematic reviews that examined adults receiving care for their complex wounds were included. Two reviewers independently screened the literature, abstracted data, and assessed study quality using the Assessment of Multiple Systematic Reviews (AMSTAR) tool.ResultsOverall, 99 systematic reviews were included after screening 6,200 titles and abstracts and 422 full-texts; 54 were systematic reviews with a meta-analysis (including data on over 54,000 patients) and 45 were systematic reviews without a meta-analysis. Overall, 44% of included reviews were rated as being of high quality (AMSTAR score ≥8). Based on data from systematic reviews including a meta-analysis with an AMSTAR score ≥8, promising interventions for complex wounds were identified. These included bandages or stockings (multi-layer, high compression) and wound cleansing for venous leg ulcers; four-layer bandages for mixed arterial/venous leg ulcers; biologics, ultrasound, and hydrogel dressings for diabetic leg/foot ulcers; hydrocolloid dressings, electrotherapy, air-fluidized beds, and alternate foam mattresses for pressure ulcers; and silver dressings and ultrasound for unspecified mixed complex wounds. For surgical wound infections, topical negative pressure and vacuum-assisted closure were promising interventions, but this was based on evidence from moderate to low quality systematic reviews.ConclusionsNumerous interventions can be utilized for patients with varying types of complex wounds, yet few treatments were consistently effective across all outcomes throughout the literature. Clinicians and patients can use our results to tailor effective treatment according to type of complex wound. Network meta-analysis will be of benefit to decision-makers, as it will permit multiple treatment comparisons and ranking of the effectiveness of all interventions.Please see related article: http://dx.doi.org/10.1186/s12916-015-0326-3Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-015-0288-5) contains supplementary material, which is available to authorized users.

Pressure Relief, Visco-Elastic Foam with Inflated Air? A Pilot Study in a Dutch Nursing Home.

Objective: There is still little evidence regarding the type of mattress that is the best for preventing pressure ulcers (PUs). In a Dutch nursing home, a new type of overlay mattress (air inflated visco-elastic foam) was tested to analyze the opportunity for replacement of the normally used static air overlay mattress in its three-step PU prevention protocol In this small pilot the outcome measures were: healing of a category one pressure ulcer, new development or deterioration of a category one PU and need for repositioning. Methods: We included 20 nursing home residents with a new category one pressure ulcer, existing for no longer than 48 h following a consecutive sampling technic. All residents were staying for more than 30 days in the nursing home and were lying on a visco-elastic foam mattress without repositioning (step one of the 3-step protocol) at the start of the pilot study. They had not suffered from a PU in the month before. The intervention involved use of an air inflated foam overlay instead of a static air overlay (normally step 2 of the 3-step protocol). At the start; the following data were registered: age; gender; main diagnosis and presence of incontinence. Thereafter; all participating residents were checked weekly for PU healing tendency; deterioration of PUs; new PUs and need of repositioning. Only when residents showed still a category one PU after 48 h or deterioration of an existing pressure ulcer or if there was development of a new pressure ulcer, repositioning was put into practice (step 3 of the PU protocol). All residents participated during 8 weeks. Results: Seven residents developed a new pressure ulcer category one and still had a category one pressure ulcer at the end of the study period. One resident developed a pressure ulcer category 2. Fifteen residents needed repositioning from one week after start of the study until the end of the study. Conclusions: Overall 40% of the residents developed a pressure ulcer. Seventy five percent of the residents started with repositioning because there was no healing tendency of their category one PU diagnosed at the start of the pilot. Because this new type of overlay mattress resulted in an increased PU incidence, and almost standard need of repositioning with accompanied high costs, this type of overlay mattress gives no benefit above the traditional visco-elastic foam mattresses in combination with the originally used static air overlay.

Bone geometry on the contact stress in the shoulder for evaluation of pressure ulcers: Finite element modeling and experimental validation

This research presents the finite element modeling (FEM) of human-specific computed tomography (CT) data to study the effect of bone prominences on contact stress in the shoulder for prevention of pressure ulcers. The 3D geometry of scapula, skin, and surrounding soft tissues in the shoulder was reconstructed based on the anonymous CT data of a human subject in a prone posture (without loading on the shoulder) for FEM analysis of the contact stress. FEM analysis results show that the maximum stress is located at the prominence of the scapula with sharp bone geometry. This demonstrates that stress concentration at the bone prominence is a significant factor to cause the high contact stress, which is a source for pressure ulcers. For experimental validation, a physical shoulder model manufactured by 3D printing of the bone geometry and the mold for molding of tissue-mimicking silicone was developed. Compression tests of the mattress foam and silicone were conducted to find the nonlinear stress–strain relations as inputs for FEM. Experiments of compressing the shoulder model against the foam were carried out. Three flexible force sensors were embedded inside the model to measure the contact forces and compared to the FEM predictions. Results show that the FEM predicted forces match well with the experimental measurements and demonstrate that FEM can accurately predict the stress distributions in the shoulder to study the effect of bone geometry on the inception of pressure ulcers.