Project description:The aims of this study were to identify, assess, and summarise available evidence about the effectiveness of static air mattress overlays to prevent pressure ulcers. The primary outcome was the incidence of pressure ulcers. Secondary outcomes included costs and patient comfort. This study was a systematic review. Six electronic databases were consulted: Cochrane Library, EMBASE, PubMed (Medline), CINAHL (EBSCOhost interface), Science direct, and Web of Science. In addition, a hand search through reviews, conference proceedings, and the reference lists of the included studies was performed to identify additional studies. Potential studies were reviewed and assessed by 2 independent authors based on the title and abstract. Decisions regarding inclusion or exclusion of the studies were based on a consensus between the authors. Studies were included if the following criteria were met: reporting an original study; the outcome was the incidence of pressure ulcer categories I to IV when using a static air mattress overlay and/or in comparison with other pressure-redistribution device(s); and studies published in English, French, and Dutch. No limitation was set on study setting, design, and date of publication. The methodological quality assessment was evaluated using the Critical Appraisal Skills Program Tool. Results were reported in a descriptive way to reflect the exploratory nature of the review. The searches included 13 studies: randomised controlled trials (n = 11) and cohort studies (n = 2). The mean pressure ulcer incidence figures found in the different settings were, respectively, 7.8% pressure ulcers of categories II to IV in nursing homes, 9.06% pressure ulcers of categories I to IV in intensive care settings, and 12% pressure ulcers of categories I to IV in orthopaedic wards. Seven comparative studies reported a lower incidence in the groups of patients on a static air mattress overlay. Three studies reported a statistical (P < .1) lower incidence compared with a standard hospital mattress (10 cm thick, density 35 kg/m3 ), a foam mattress (15 cm thick), and a viscoelastic foam mattress (15 cm thick). No significant difference in incidence, purchase costs, and patient comfort was found compared with dynamic air mattresses. This review focused on the effectiveness of static air mattress overlays to prevent pressure ulcers. There are indications that these mattress overlays are more effective in preventing pressure ulcers compared with the use of a standard mattress or a pressure-reducing foam mattress in nursing homes and intensive care settings. However, interpretation of the evidence should be performed with caution due to the wide variety of methodological and/or reporting quality levels of the included studies.
Project description:The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools.
Project description:When immobile or neuropathic patients are supported by beds or chairs, their soft tissues undergo deformations that can cause pressure ulcers. Current support surfaces that redistribute under-body pressures at vulnerable body sites have not succeeded in reducing pressure ulcer prevalence. Here we show that adding a supporting lateral pressure can counter-act the deformations induced by under-body pressure, and that this 'pressure equalisation' approach is a more effective way to reduce ulcer-inducing deformations than current approaches based on redistributing under-body pressure. A finite element model of the seated pelvis predicts that applying a lateral pressure to the soft tissue reduces peak von Mises stress in the deep tissue by a factor of 2.4 relative to a standard cushion (from 113 kPa to 47 kPa)-a greater effect than that achieved by using a more conformable cushion, which reduced von Mises stress to 75 kPa. Combining both a conformable cushion and lateral pressure reduced peak von Mises stresses to 25 kPa. The ratio of peak lateral pressure to peak under-body pressure was shown to regulate deep tissue stress better than under-body pressure alone. By optimising the magnitude and position of lateral pressure, tissue deformations can be reduced to that induced when suspended in a fluid. Our results explain the lack of efficacy in current support surfaces and suggest a new approach to designing and evaluating support surfaces: ensuring sufficient lateral pressure is applied to counter-act under-body pressure.
Project description:BackgroundPressure ulcers affect approximately 10% of people in hospitals and older people are at highest risk. A correlation between inadequate nutritional intake and the development of pressure ulcers has been suggested by several studies, but the results have been inconsistent.ObjectivesTo evaluate the effects of enteral and parenteral nutrition on the prevention and treatment of pressure ulcers.Search methodsIn March 2014, for this first update, we searched The Cochrane Wounds Group Specialised Trials Register, the Cochrane Central register of Controlled Trials (The Cochrane Library), the Database of Abstracts of Reviews of Effects (DARE) (The Cochrane Library), the Health Technology Assessment Database (HTA) (The Cochrane Library), the Cochrane Methodology Register (The Cochrane Library), NHS Economic Evaluation Database (The Cochrane Library), Ovid Medline, Ovid Embase and EBSCO CINAHL. No date, language or publication status limits were applied.Selection criteriaRandomised controlled trials (RCTs) evaluating the effects of enteral or parenteral nutrition on the prevention and treatment of pressure ulcers, which measured the incidence of new ulcers, ulcer healing or changes in pressure ulcer severity. There were no restrictions on types of patient, setting, date, publication status or language.Data collection and analysisTwo review authors independently screened for inclusion, and disagreement was resolved by discussion. Two review authors independently extracted data and assessed quality using the Cochrane Collaboration tool for assessing risk of bias.Main resultsWe included 23 RCTs, many were small (between 9 and 4023 participants, median 88) and at high risk of bias.Eleven trials compared a combination of nutritional supplements, consisting of a minimum of energy and protein in different dosages, for the prevention of pressure ulcers. A meta-analysis of eight trials (6062 participants) that compared the effects of mixed nutritional supplements with standard hospital diet found no clear evidence of an effect of supplementation on pressure ulcer development (pooled RR 0.86; 95% CI 0.73 to 1.00; P value 0.05; I(2) = 13%, random effects). This outcome is at unclear or high risk of bias.Fourteen trials evaluated the effects of nutritional supplements on the healing of existing pressure ulcers: seven trials examined mixed nutritional supplements, three the effects of proteins, two trials examined zinc, and two studies examined ascorbic acid. The included trials were heterogeneous with regard to participants, interventions, comparisons and outcomes and meta-analysis was not appropriate. There was no clear evidence of an improvement in pressure ulcer healing from the nutritional supplements evaluated in any of these individual studies.Authors' conclusionsThere is currently no clear evidence of a benefit associated with nutritional interventions for either the prevention or treatment of pressure ulcers. Further trials of high methodological quality are necessary.
Project description:The generation of electrical voltage through the flow of an electrolyte over a charged surface may be used for energy transduction. Here, we show that enhanced electrical potential differences (i.e., streaming potential) may be obtained through the flow of salt water on liquid-filled surfaces that are infiltrated with a lower dielectric constant liquid, such as oil, to harness electrolyte slip and associated surface charge. A record-high figure of merit, in terms of the voltage generated per unit applied pressure, of 0.043 mV Pa-1 is obtained through the use of the liquid-filled surfaces. In comparison with air-filled surfaces, the figure of merit associated with the liquid-filled surface increases by a factor of 1.4. These results lay the basis for innovative surface charge engineering methodology for the study of electrokinetic phenomena at the microscale, with possible application in new electrical power sources.