449 research outputs found

    Hydrodynamics of steep streams with planar coarse-grained beds: Turbulence, flow resistance, and implications for sediment transport

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    The hydraulics of steep mountain streams differ from lower gradient rivers due to shallow and rough flows, energetic subsurface flow, and macro-scale form drag from immobile boulders and channel- and bed-forms. Heightened flow resistance and reduced sediment transport rates in steep streams are commonly attributed to macro-scale form drag; however, little work has explored steep river hydrodynamics in the absence of complex bed geometries. Here we present theory for the vertical structure of flow velocity in steep streams with planar, rough beds that couples surface and subsurface flow. We test it against flume experiments using a bed of fixed cobbles over a wide range of bed slopes (0.4 – 30%). Experimental flows have a nearly logarithmic velocity profile far above the bed; flow velocity decreases less than logarithmically towards the bed and is non-zero at the bed surface. Velocity profiles match theory derived using a hybrid eddy-viscosity model, in which the mixing length is a function of height above the bed and bed roughness. Subsurface flow velocities are large (> 1 m/s) and follow a modified Darcy-Brinkman-Forchheimer relation that accounts for channel slope and shear from overlying surface flow. Near-bed turbulent fluctuations decrease for shallow, rough flows and scale with the depth-averaged flow velocity rather than bed shear velocity. Flow resistance for rough, planar beds closely matches observations in natural steep streams despite the lack of bed- or channel-forms in the experiments, suggesting that macro-scale form drag is smaller than commonly assumed in stress partitioning models for sediment transport

    Reducing the burden of acute respiratory distress syndrome: The case for early intervention and the potential role of the emergency department

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    The mortality for acute respiratory distress syndrome (ARDS) remains unacceptably high. Success in clinical trials has been limited, resulting in a lack of effective therapies to treat the syndrome. The projected increase in mechanically ventilated patients and global need for critical care services suggests that the clinical and research landscape in ARDS can no longer be confined to the intensive care unit (ICU). A demonstrable minority of patients present to the emergency department (ED) with ARDS, and ARDS onset typically occurs shortly after ICU admission. Furthermore, the ED is an entry point for many of the highest risk patients for ARDS development and progression. These facts, combined with prolonged lengths of stay in the ED, suggest that the ED could represent a window of opportunity for treatment and preventive strategies, as well as clinical trial enrollment. This review aims to discuss some of the potential strategies which may prevent or alter the trajectory of ARDS, with a focus on the potential role the ED could play in reducing the burden of this syndrome

    Lower tidal volume at initiation of mechanical ventilation may reduce progression to acute respiratory distress syndrome: A systematic review

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    INTRODUCTION: The most appropriate tidal volume in patients without acute respiratory distress syndrome (ARDS) is controversial and has not been rigorously examined. Our objective was to determine whether a mechanical ventilation strategy using lower tidal volume is associated with a decreased incidence of progression to ARDS when compared with a higher tidal volume strategy. METHODS: A systematic search of MEDLINE, EMBASE, CINAHL, the Cochrane Library, conference proceedings, and clinical trial registration was performed with a comprehensive strategy. Studies providing information on mechanically ventilated patients without ARDS at the time of initiation of mechanical ventilation, and in which tidal volume was independently studied as a predictor variable for outcome, were included. The primary outcome was progression to ARDS. RESULTS: The search yielded 1,704 studies, of which 13 were included in the final analysis. One randomized controlled trial was found; the remaining 12 studies were observational. The patient cohorts were significantly heterogeneous in composition and baseline risk for developing ARDS; therefore, a meta-analysis of the data was not performed. The majority of the studies (n = 8) showed a decrease in progression to ARDS with a lower tidal volume strategy. ARDS developed early in the course of illness (5 hours to 3.7 days). The development of ARDS was associated with increased mortality, lengths of stay, mechanical ventilation duration, and nonpulmonary organ failure. CONCLUSIONS: In mechanically ventilated patients without ARDS at the time of endotracheal intubation, the majority of data favors lower tidal volume to reduce progression to ARDS. However, due to significant heterogeneity in the data, no definitive recommendations can be made. Further randomized controlled trials examining the role of lower tidal volumes in patients without ARDS, controlling for ARDS risk, are needed. 2013 Fuller et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

    Body temperature patterns as a predictor of hospital-acquired sepsis in afebrile adult intensive care unit patients: A case-control study

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    INTRODUCTION: Early treatment of sepsis improves survival, but early diagnosis of hospital-acquired sepsis, especially in critically ill patients, is challenging. Evidence suggests that subtle changes in body temperature patterns may be an early indicator of sepsis, but data is limited. The aim of this study was to examine whether abnormal body temperature patterns, as identified by visual examination, could predict the subsequent diagnosis of sepsis in afebrile critically ill patients. METHODS: Retrospective case-control study of 32 septic and 29 non-septic patients in an adult medical and surgical ICU. Temperature curves for the period starting 72 hours and ending 8 hours prior to the clinical suspicion of sepsis (for septic patients) and for the 72-hour period prior to discharge from the ICU (for non-septic patients) were rated as normal or abnormal by seven blinded physicians. Multivariable logistic regression was used to compare groups in regard to maximum temperature, minimum temperature, greatest change in temperature in any 24-hour period, and whether the majority of evaluators rated the curve to be abnormal. RESULTS: Baseline characteristics of the groups were similar except the septic group had more trauma patients (31.3% vs. 6.9%, p = .02) and more patients requiring mechanical ventilation (75.0% vs. 41.4%, p = .008). Multivariable logistic regression to control for baseline differences demonstrated that septic patients had significantly larger temperature deviations in any 24-hour period compared to control patients (1.5°C vs. 1.1°C, p = .02). An abnormal temperature pattern was noted by a majority of the evaluators in 22 (68.8%) septic patients and 7 (24.1%) control patients (adjusted OR 4.43, p = .017). This resulted in a sensitivity of 0.69 (95% CI [confidence interval] 0.50, 0.83) and specificity of 0.76 (95% CI 0.56, 0.89) of abnormal temperature curves to predict sepsis. The median time from the temperature plot to the first culture was 9.40 hours (IQR [inter-quartile range] 8.00, 18.20) and to the first dose of antibiotics was 16.90 hours (IQR 8.35, 34.20). CONCLUSIONS: Abnormal body temperature curves were predictive of the diagnosis of sepsis in afebrile critically ill patients. Analysis of temperature patterns, rather than absolute values, may facilitate decreased time to antimicrobial therapy

    Awareness and bispectral index (BIS) monitoring in mechanically ventilated patients in the emergency department and intensive care unit: A systematic review protocol

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    INTRODUCTION: Accidental awareness with recall is one of the most feared complications for patients undergoing general anaesthesia and can lead to post-traumatic stress disorder in up to 70% of patients experiencing it. To reduce the incidence of awareness with recall, the bispectral index monitor is recommended for patients receiving total intravenous anaesthetics, especially those receiving neuromuscular blockers. While extensive investigation into awareness and bispectral index monitoring has occurred for operating room patients, this has not extended to other clinical arenas where sedated and mechanically ventilated patients are cared for, namely the intensive care unit and emergency department. The purpose of this systematic review is to assess the world\u27s literature to determine the incidence of awareness with paralysis in mechanically ventilated patients and the impact of bispectral index monitoring for reducing this complication. METHODS AND ANALYSIS: Randomised trials and non-randomised studies are eligible for inclusion. With aid from a medical librarian, an electronic search will include Ovid Medline, Embase.com, Scopus, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials. To find data published in abstract form, literature from professional society conferences (2010-2019) will be manually searched. Two authors will independently review search results and consensus will be reached with assistance from a third author, as needed. Heterogeneity and publication bias will be assessed and reported. If possible and appropriate, a meta-analysis of the data will be conducted for quantitative data analysis. ETHICS AND DISSEMINATION: The proposed systematic review does not require ethical approval, as it is conducted at the study level and does not involve individual patient-level data. Results will be disseminated by data sharing via academically established means, presentation at local and national scientific meetings and publication as a peer-reviewed manuscript. PROSPERO REGISTRATION NUMBER: The protocol has been submitted to International Prospective Register of Systematic Reviews and is awaiting registration

    Shared care in mental illness: A rapid review to inform implementation

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    <p>Abstract</p> <p>Background</p> <p>While integrated primary healthcare for the management of depression has been well researched, appropriate models of primary care for people with severe and persistent psychotic disorders are poorly understood. In 2010 the NSW (Australia) Health Department commissioned a review of the evidence on "shared care" models of ambulatory mental health services. This focussed on critical factors in the implementation of these models in clinical practice, with a view to providing policy direction. The review excluded evidence about dementia, substance use and personality disorders.</p> <p>Methods</p> <p>A rapid review involving a search for systematic reviews on The Cochrane Database of Systematic Reviews and Database of Abstracts of Reviews of Effects (DARE). This was followed by a search for papers published since these systematic reviews on Medline and supplemented by limited iterative searching from reference lists.</p> <p>Results</p> <p>Shared care trials report improved mental and physical health outcomes in some clinical settings with improved social function, self management skills, service acceptability and reduced hospitalisation. Other benefits include improved access to specialist care, better engagement with and acceptability of mental health services. Limited economic evaluation shows significant set up costs, reduced patient costs and service savings often realised by other providers. Nevertheless these findings are not evident across all clinical groups. Gains require substantial cross-organisational commitment, carefully designed and consistently delivered interventions, with attention to staff selection, training and supervision. Effective models incorporated linkages across various service levels, clinical monitoring within agreed treatment protocols, improved continuity and comprehensiveness of services.</p> <p>Conclusions</p> <p>"Shared Care" models of mental health service delivery require attention to multiple levels (from organisational to individual clinicians), and complex service re-design. Re-evaluation of the roles of specialist mental health staff is a critical requirement. As expected, no one model of "shared" care fits diverse clinical groups. On the basis of the available evidence, we recommended a local trial that examined the process of implementation of core principles of shared care within primary care and specialist mental health clinical services.</p
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