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Influence of temperature on vascular density at the sacrum and heel
No full textIntroduction: localised damage to the skin through a combination of sustained pressure and repeated shearing forces can lead to the development of pressure ulcers (PUs). In the UK, the cost of treating PUs and other hard-to-heal (chronic) wounds is ~£8 billion annually.1 Animal studies have identified the use of localised cooling to influence the skin's tolerance to mechanical loading by reducing the tissue's metabolic demands.2 However, the mechanisms by which cooling may enhance skin tolerance to loading and shearing forces remain poorly understood. Furthermore, the efficacy of cooling may differ across populations and anatomical sites. The aim of this study was to examine how different levels of localised cooling influence microvascular properties in younger and older adults.Method: younger and older adults with no health conditions underwent an in vivo characterisation of vascular density (expressed as a percentage of tissue comprising blood vessels against the depth of detection) at two skin sites: the sacrum and posterior heel. For the evaluation, three different local temperatures were used: 38°C, 24°C and 16°C. Vascular density was assessed using a dynamic optical coherence tomography scanner. The sacrum underwent a protocol to cause pressure-induced ischaemia and post-occlusive hyperaemia.3 The heel underwent a standardised repeated shearing protocol.4 Peak vascular density data were analysed using a two-way analysis of variance to assess the interaction between temperature condition and anatomical site.Results: in this study, 22 younger (mean age: 25±4 years; mean weight: 71±9kg; mean height: 176±9cm) and 19 older adults (mean age: 65±4 years; mean weight: 70±14kg; mean height: 171±10cm) were included. There was a main effect of temperature (p<0.001) on peak vascular density and an interaction effect with skin site, where vascular density was greater in the sacrum compared to the heel at all temperatures (p<0.001). Post hoc analysis revealed 24°C (8.9±3.5%) at the sacrum was lower in terms of peak vascular density than both 16°C (11.7±4.1%; mean difference: 2.3%; 95% confidence interval (CI): –3.6, 1.0; p<0.001) and 38°C (11.1±5.4%; mean difference: 2.9%; 95% CI: –5.1, 0.6; p=0.008). At the heel, vascular density at 16°C (3.2±2.3%) was lower than 24°C (5.0±4.1%; mean difference: 1.8%; 95% CI: –3.1, 0.5); p=0.005) and 38°C (7.9±8.7%; mean difference: 4.7%; 95% CI: –7.1, 2.4; p=0.005). Depth at peak vascular density was 0.4mm at the sacrum and 0.6mm at the heel.Conclusion: findings demonstrated there was an effect of temperature on vascular density, which was dependent on skin site. These data also highlight differences in the depth of the vascular density profiles, with more superficial microvasculature observed at the sacrum. These results indicate there were distinct microvascular responses to sustained pressure and shearing forces at two skin sites at risk of PU development, which could be used to inform the efficacy of skin cooling in maintaining skin tissue viability
Severe viral infections requiring intensive care unit admissions- aetiology, co-infections, respiratory interventions and outcomes
No full textIntroduction: severe viral infections are common in patients requiring admission to intensive care units (ICU). Furthermore, these patients often have additional secondary or co-infections. Despite their prevalence, it remains uncertain to what extent those additional infections contribute to worse outcomes for patients with severe viral infections requiring ICU admission. This study aims to characterise severe viral infections requiring admission to intensive care, and describe their viral aetiology, the incidence of additional infections, and their clinical outcomes.Methods: this retrospective single-centre cohort included consecutive adults admitted to the intensive care unit (ICU) with a positive polymerase chain reaction (PCR) test for viral infection from 2015 to 2024. Patients with SARS-CoV-2 were not included in this analysis. The data were retrieved from all available electronic databases. Patients were further stratified to compare severe viral infections alone to those with other microbiology confirmed co-infection (within 48 h of admission) and secondary infection (48 h after ICU admission). Results: we identified 222 with positive PCR for viral infection admitted to ICU. The majority were admitted with radiographic evidence of pneumonia (73.0%). Rhinovirus (28.4%), influenza A (18.5%), and RSV (16.2%) were the most common viral pathogens. Of the total, 149 patients had viral infection alone, 50 had co-infections, and 23 developed secondary infections. 30-day and ICU mortality were similar for viral alone, co-infection and secondary infection groups. Although those with secondary infection had a greater hospital and ICU length of stay, this was not reflected in the duration of mechanical ventilation or 30-day hospital mortality. Conclusion: in our large cohort of severe viral infections where Rhinovirus was the most common pathogen. This patient population constitute a high burden of respiratory support. The study also characterised 22.5% had co-infection, and 10% had subsequent secondary infection. While patients with secondary infections had prolonged ICU and hospital stay, the 30-day mortality was similar between all groups.</p
Translational framework for implementation evaluation and research: a critical approach to patient-centred equity design
No full textBackgroundThe field of implementation research has recently seen much interest in equity, with a strong emphasis on recognising and responding to disparities in care. Recent studies highlight the role of macro-level processes that translate meso-level institutional behaviours to micro-level healthcare practices, and that are generative of health and care inequities. They emphasise challenges patient-centredness and underscore the need for justice-oriented intervention design to address disparities and promote equitable care.AimTo develop a patient-centred and justice-informed approach to the design of complex healthcare interventions and innovations in service delivery.MethodPatient-centred Equity Design was developed in five stages. Sociological, public health, and implementation science theories explaining the generation of modifiable inequities were identified, and relevant explanatory constructs were extracted from them and organised into a determinant framework. Framework elements were then translated into (a) process models characterizing causal mechanisms of systemic inequities; (b) generative principles to guide equity- and patient-centred interventions and services; and (c) critical design questions to appraise the ways that inequities are embedded in healthcare interventions and services.ResultsDevelopment work led to a determinant framework linking macro-level processes to meso- and micro-level healthcare inequities, and these were visualized in process models. The framework informed principles for the promotion of equitable, patient-centred interventions: fostering civility and dependability, ensuring clarity and continuity, and reducing workload and complexity. Four critical questions address relational inequalities, participation barriers, role expectations, and restitution for inequities. These were translated into proposed content for a simple appraisal tool to support the equitable design and evaluation of healthcare interventions and services.ConclusionPatient-centred Equity Design integrates sociology, social justice, and implementation science to create equity-focused healthcare interventions. It offers a determinant framework, process models, generative principles, and critical questions to guide design. While not a validated tool, it enhances intervention development and service delivery, with potential for future Medical Research Council Framework integration. Patient- centred Equity Design provides actionable generative design principles to centre patient and caregiver experiences within intervention development, emphasizing restitution for inequities
Community engagement in maternal and perinatal death surveillance and response: a realist review
No full textBackgroundCommunity engagement in maternal and perinatal death surveillance and response (MPDSR) could support health systems in providing people-centred care and ensure accountability for the prevention of maternal and perinatal deaths. Although community engagement activities in MPDSR have been described, the literature does not adequately explain which community engagement in MPDSR strategies succeed, the contexts in which they work, the outcomes they produce, and for whom.MethodsWe conducted a realist review, which involved the identification and refinement of programme theories. An initial literature search identified four initial programme theories (IPTs) that explain how community engagement works in the different parts of the MPDSR cycle.Six databases (Medline, Embase, Scopus, Global Health, CINAHL Plus and Web of Science) and Google were searched for papers and grey literature published between 2004 and August 2022. We used retroductive analysis on included articles to support the identification of generative causation using the heuristic of ‘context-mechanism-outcome configuration’ (CMOCs), which explained what mechanisms were triggered in different contexts and the outcomes that were produced. The findings were then used to refine the IPTs and produce final programme theories.ResultsForty-five articles from 40 studies reported some form of community engagement in MPDSR. We identified 20 CMO configurations that were synthesised into five programme theories:(1)Fear of blame demotivates community members and health professionals from engaging in MPDSR.(2)Dialogue between health professionals and community members improves collaboration and empowers community members to propose innovative solutions.(3)Trusted social connections between bereaved families and community volunteers enables them to identify and report deaths.(4)Financial and non-financial incentives motivate community members and health professionals to engage in MPDSR.(5)Community engagement is more sustainable when it is routinised and integrated into the health system.ConclusionImplementing community engagement in MPDSR requires a systems approach that addresses the five Programme Theories collectively, rather than implementing community engagement in specific parts of the MPDSR cycle as our initial programme theories had suggested. Establishing conducive participatory spaces that promote dialogue, trust and minimise blame culture is critical for the success of community engagement in MPDSR programmes. Community members can be engaged in MPDSR processes in health facilities and community settings and high- and low-income countries
High-efficiency mid-infrared wavelength conversion in silicon waveguides
No full textHigh-efficiency wavelength conversion into the 2 μm region has been achieved through Raman enhanced four-wave mixing in a planar silicon waveguide. By aligning the FWM phase-matching conditions with the Raman gain bandwidth, a wavelength conversion efficiency of −25 dB was achieved with a continuous-wave pump power of only ∼45 mW. The maximum Raman enhancement in this hybrid wavelength conversion process is ∼7 dB. Simulations show that by further optimizing the planar waveguide dispersion profile, the wavelength conversion efficiency could be increased to ∼−11 dB using a standard continuous-wave pump source
High-resolution simulation of air-breathing rotating detonation engines
No full textRotating detonation engines (RDEs) use one or multiple spinning detonations to burn propellants in an annular combustion chamber. RDEs are of great interest for hypersonic propulsion as detonation combustion involves a gain in total pressure. Yet, the complex energetic interplay between the leading shock wave and the combustion front in a detonation wave and its propagation speed of around 2000m/s make the experimental investigation of RDEs quite challenging. Numerical simulations are therefore of crucial importance for predicting stable RDE operation at the design stage. Here, we conduct predictive 3D numerical simulations of non-premixed detonation combustion in RDEs using our parallel bock-structured finite volume adaptive mesh refinement framework AMROC, which solves the thermally perfect multi-component Navier-Stokes equations with a detailed chemical model as governing equations on body-fitted curvilinear meshes with dynamic mesh adapation following the detonation fronts. After validating the methodology for a hydrogen-air RDE with available experimental data, we implement constant temperature wall boundary conditions and demonstrate that the number of detonation waves remains unchanged, and that the average detonation velocity deficit rises only slightly, confirming that RDEs can be cooled considerably without significantly affecting the detonation efficiency. Finally, we present simulations with different back pressures of a cooled prototype RDE combustion chamber intended for a laboratory turbine engine running on ethylene and air. The ethylene-air simulations demonstrate that despite a considerably reduced detonation velocity in this very realistic configuration, gains in total pressure at the outlet of 13.3\% and 18.1\% can still be measured, which demonstrates the benefit of the RDE concept for turbine engines quite clearly
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