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Search Results: 1 - 10 of 27335 matches for " Martin Chapman "
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Greening critical care
Martin Chapman, Alison Chapman
Critical Care , 2011, DOI: 10.1186/cc9409
Abstract: Many have argued that the risks to health from climate change are overwhelmingly negative. At the conclusion of the United Nations Climate Change Conference in Copenhagen (COP15), which took place in December 2009, there was no agreed- upon plan of action that would avoid a critical 2% rise in greenhouse gas (GHG) emissions globally. Our international leaders did not step up to the plate; rather, they produced an Accord [1] that will neither solve the problem nor appease the critics [2]. The implications for health [3-5], in light of this, are similar to implications for the economy [6] and the earth's natural systems - they are dire.Our viewpoint is that it is better to be part of the solution than part of the problem, even if there is a dearth of evidence stating that any of the described actions will generate a measureable outcome. When using the term green, we are referring to practices and policies that do not negatively affect our environment. It is hoped that this paper will map out ways to green up an intensive care unit (ICU) and reduce the effect of environmental toxins on our patients, with suggestions targeted at individuals and their institutions. Although sustainable critical care may sound like an oxymoron to many of us, we cannot ignore our responsibilities on the basis that greening an ICU is too difficult. There are steps that can be taken at all levels, setting an example to influence our collective behaviour. If an ICU can go green then there is little excuse for the rest of the hospital not to follow suit.The gauntlet is thrown down.ICUs are not, in our experience, at the forefront of sustainable environmental management. Possibly the only published mention of intensive care and the environment was when, during the Copenhagen Conference, India's Environment Minister said that the Kyoto pact was in 'Intensive Care, if not dead' when negotiations on extending the pact had stalled [7].We are not suggesting that patient care should be in any way com
Hemorrhagic shock: a review
Martin Chapman
Critical Care , 2004, DOI: 10.1186/cc2898
Abstract: Damage control surgery in trauma and embolization are certainly useful tools in the control of bleeding.Pharmacological manipulation of the coagulation system is a rapidly expanding field of research. Activated recombinant factor VII (Factor VIIa) is a hemostatic agent originally developed for the hemophilia population, but it is emerging as a very effective way of treating uncontrolled hemorrhage in patients without pre-existing factor deficiencies. A heterogeneous case series of major hemorrhage was reported last year, in which 80% of the cases given Factor VIIa responded with complete or partial cessation of bleeding [2]. Data from the trauma environment with massive bleeding suggest a useful role for Factor VIIa [3], and further studies are ongoing.None declared.H David Reines, Marian Wulf-Gutierrrez and Guillermo Gutierrez.We thank Dr Chapman for his comments on new approaches to control hemorrhage. We agree that conservation of blood and blood products is not just an economic concern, but it is necessary to protect a limited resource and to prevent untoward effects of such products. Our sections on hypertonic saline and the use of blood substitutes were meant to address this issue directly. We limited our discussion to a general discussion of hemorrhagic shock and did not specifically address surgical approaches to the control of bleeding. 'Damage control' and packing is a valid concept in the treatment of severely injured patients with hemorrhage [4]. This approach was frequently used in battlefields, and has become more popular in civilian injury as a method for preventing death from coagulopathy and hypothermia in the operating room. The use of radiological embolization as a technique to control ongoing hemorrhage from solid organs such as the spleen and the liver has also supplemented its use in pelvic hemorrhage. This technique is not necessarily an ideal therapy for patients who are in shock. Operative intervention is still necessary in unstable patients
Why is early goal-directed therapy successful – is it the technology?
Martin Chapman, David Gattas, Ganesh Suntharalingam
Critical Care , 2005, DOI: 10.1186/cc3726
Abstract: Early resuscitation in sepsis is standard practice [3]. If the treatment effect reported by Rivers and coworkers is not due to bias in the study design, then to what part(s) of the resuscitation 'package' is the benefit attributable? Opinions vary regarding the contribution an oximetric catheter makes in severe sepsis [4]. Previous studies of therapy directed by mixed venous saturation have found no similar improvement in outcome [5,6]. It seems more likely to us that the timing of resuscitation is the crucial aspect rather than the technology employed [7,8].Another aspect of the study by Rivers and colleagues that has attracted discussion is the difference in the use of blood transfusion between the groups. The use of blood to improve oxygen delivery is controversial; a liberal transfusion strategy is not beneficial in general intensive care patients [9] and the ability of stored red cells to improve oxygen delivery acutely is known to be impaired [10]. Finally, although blinding in a trial of resuscitation is very difficult to achieve, unfortunately the capacity for this methodological shortcoming to introduce bias remains undiminished.In light of these considerations, we present a review, paired with the Q&A, which forms part of a process of critical review that any new health technology should be subjected to by the critical care community. In our view, we must remain critical; ScvO2 monitoring cannot be assumed to be central to the success of EGDT [11]. Other goals are presented in the review that are feasible and less invasive. It will take time for ScvO2 monitoring to find its rightful place.EGDT = early goal-directed therapy; ScvO2 = central venous oxygen saturation.The author(s) declare that they have no competing interests.
Health technology and credibility
Martin Chapman, David Gattas, Ganesh Suntharalingam
Critical Care , 2004, DOI: 10.1186/cc2842
Abstract: Credibility is of prime concern, in an area where marketing materials generally include some bias. In addition, the traditional clinician's perspective is not without its own uncertainties, covering a spectrum from unbiased yet inexperienced to experienced but partisan with industry. So how can we truly assess technology in a way that is practically relevant and reliable?The format of the forthcoming technology assessments will be pairs of articles: a set questionnaire answered by the developer alongside a reflective assessment written by an expert chosen for their independence. This choice of expert is one of the features of this new venture. We hope that by careful choice of reviewer we will retain the reader's trust and support clinical decision-making. The selection of experts will probably involve recruiting new clinicians who are less tarnished by the tensions of research and industry funding. This will sometimes mean avoiding the usual giants of our field. In so doing, however, we hope to remain true to the original agenda. This extends to the Journal's choice of editorial team for the section. We would consider ourselves free from professional conflict.As an additional aid to keeping abreast of the rapid evolution of technology, we will be running a regular item on innovations. The first of these appears in this edition. This will attempt to introduce novel technologies or important advances in technologies that are already established.None declared.
Innovations in technology for critical care medicine
Martin Chapman, David Gattas, Ganesh Suntharalingam
Critical Care , 2004, DOI: 10.1186/cc2843
Abstract: This new triannual section will examine emerging health technologies. It is not meant to be a comprehensive scan of the horizon, but rather a selection of clinically important examples of advances in critical care technology.The blurring of specialty domains is becoming more obvious. A good example of this is the use of ultrasound by intensivists [1]. Portable ultrasound as an extension of the physical examination is a fast growing area of expertise. A recent Canadian report [2] summarized several new hand-carried ultrasound units for point of care (POC) cardiac examination, including OptiGo? (Philips Medical Systems, Andover, MA, USA), which has a laptop design, colour Doppler and smartcard storage (Fig. 1). In a prototype study conducted by Rugolotto and coworkers [3], the handheld device was compared with standard echocardiography in 121 patients. The studies were performed by echocardiographers with level II and III training. Parameters of ventricular and valvular function with two-dimensional and colour Doppler were graded on a point system using both devices. There were statistically significant differences between the two methods, although these were clinically minor in degree. The investigators concluded that the handheld device did represent an acceptable tool for conducting a focused assessment of a limited number of parameters of structure and function.However, conflicting results were reported from another study with the same prototype unit [4]. Spencer and coworkers compared the diagnostic power of physical examination, POC echocardiography and standard echocardiography when performed by cardiologists. POC echocardiography was an improvement on physical examination but still missed 21% of major cardiovascular findings as compared with standard echocardiography. This emphasizes some of the difficulties in implementing new devices, among which are defining the limitations of use and ensuring standards in training.Intensive care unit (ICU) staff have been
Scanning the horizon: emerging hospital-wide technologies and their impact on critical care
Ganesh Suntharalingam, Jonathan Cousins, David Gattas, Martin Chapman
Critical Care , 2004, DOI: 10.1186/cc3046
Abstract: This series of articles provides regular surveillance of new technologies which may impact on critical care. Several countries have developed national horizon scanning systems to identify and monitor new health technologies. There is variation in how these centres gather information, but a consistent set of high priority sources has been identified [1]. For the purposes of this article, the outputs of major health technology assessment centres, national regulatory authorities, and recognized scientific news sources (Table 1) were systematically searched for developments relevant to acute and critical care. This was combined with a manual medical literature search, along key editorial themes subjectively selected for this issue.Point-of-care testing is a major emerging theme throughout the health sector, encompassing both new diagnoses and monitoring of known diseases and their treatment. Areas of research range from the potentially lucrative markets for outpatient, 'office'-based and patient self-testing, through to in-hospital diagnostics, which include both rapid access analysis of traditionally laboratory bound diagnostics and direct patient imaging. Both aspects are particularly relevant to critical care clinicians, who rely on time sensitive diagnosis and treatment in a hyper-acute setting. An example of bedside imaging in cardiac assessment has already been cited in the first article of the present series [2]. Sample analysis, meanwhile, is rapidly developing to encompass bedside biochemical markers, physiological homeostasis monitoring, and novel ultra-rapid forms of infectious disease diagnosis.B-type natriuretic peptide can be a rapid and effective marker of ventricular strain and heart failure [3], and can now be measured using a point-of-care diagnostic panel (Triage BNP Test; Biosite Inc., San Diego, CA, USA). Similar current and forthcoming technologies include rapid access D-dimer assays for diagnosis of pulmonary embolism as part of a structured point
Carbon dioxide monitoring and evidence-based practice – now you see it, now you don't
David Gattas, Raj Ayer, Ganesh Suntharalingam, Martin Chapman
Critical Care , 2004, DOI: 10.1186/cc2916
Abstract: The technology required to perform capnography on expired gas is not new and its use has been considered a standard in basic anaesthetic monitoring by the American Society of Anesthesiologists since 1986 [1]. This contrasts with the use of sublingual capnometry as a detector of regional hypoperfusion [2], which is a recent application of carbon dioxide monitoring whose use should currently be considered investigational.Evidence-based medicine, defined as the integration of best research evidence with clinical expertise and patient values [3], encourages us to use all appropriate sources of data to inform best practice. Using the example of carbon dioxide monitoring and its many applications, we compare the different kinds of evidence that were required or are needed before a health technology can earn its place in clinical practice.Measurement of the magnitude and severity of adverse outcomes following undiagnosed esophageal intubation in anesthesia helped create the demand for an effective way to prevent this important problem. The use of capnography to confirm endotracheal tube placement is founded on a simple and widely understood physiologic rationale, and the appropriate level of evidence required before recommending the use of a device designed to perform this function is a demonstration that the device is safe, sensitive, and specific. The debate has long since moved on to other aspects of end-tidal capnography such as its use in prehospital settings and to the inadequate dissemination of this practice throughout critical care [4].Colorimetric indicators of end-tidal carbon dioxide are much simpler devices than gas analyzers, and rely on visible color changes in a chemical indicator that is housed within a disposable connector. As with a gas analyzer, prospective users of these devices need only see evidence that the device is safe, sensitive, and specific. Clinical experience tells us that these devices may have real additional benefits in terms of ease of u
Effect of Fracture Aperture on P-Wave Attenuation: A Seismic Physical Modelling Study
Aniekan Martin Ekanem,Xiang Yang Li,Mark Chapman,Main Ian,Jianxin Wei
ISRN Geophysics , 2014, DOI: 10.1155/2014/241279
Abstract: We used the seismic physical modelling approach to study the effect of fracture thickness or aperture on P-wave attenuation, using a laboratory scale model of two horizontal layers. The first layer is isotropic while the second layer has six fractured blocks, each consisting of thin penny-shaped chips of 3?mm fixed diameter and same thickness to simulate a set of aligned vertical fractures. The thickness of the chips varies according to the blocks while the fracture density remains the same in each block. 2D reflection data were acquired with the physical model submerged in a water tank in a direction perpendicular to the fracture strikes using the pulse and transmission method. The induced attenuation was estimated from the preprocessed CMP gathers using the QVO method, which is an extension of the classical spectral ratio method of attenuation measurement from seismic data. The results of our analysis show a direct relationship between attenuation and the fracture thickness or aperture. The induced attenuation increases systematically with fracture thickness, implying more scattering of the wave energy in the direction of increasing aperture. This information may be useful to differentiate the effect caused by thin microcracks from that of large open fractures. 1. Introduction Fractures open at depth tend to be aligned normal to the direction of minimum in situ stress acting on them [1], giving rise to seismic anisotropy. Over the years, seismic anisotropy has been increasingly used as a potential tool to characterize natural fractured hydrocarbon reservoirs (e.g., [2–5]). The equivalent medium theories of seismic wave propagation provide the basis of using seismic anisotropy to detect fractures from seismic data. One of such theories is the Hudson’s theory [6, 7] which provides a link between fracture density and measured azimuthal anisotropy. However, the theory fails to account for the issues of fracture scale lengths. For instance, many small cracks or a few large cracks within the same volume of material can result in the same fracture density. Furthermore, equal number of cracks with the same diameter but with varying thicknesses or apertures within the same volume of material can give rise to the same fracture density. In reservoir rocks, it is possible to have aligned fractures of the same density but at different scales and consequently, the investigation of the effects of the fracture scale lengths and thicknesses or apertures on seismic wave response may be of great interest in fractured reservoir characterization. An adequate understanding
Algebraic and combinatorial aspects of sandpile monoids on directed graphs
Scott Chapman,Rebecca Garcia,Luis David García-Puente,Martin E. Malandro,Ken W. Smith
Mathematics , 2011,
Abstract: The sandpile group of a graph is a well-studied object that combines ideas from algebraic graph theory, group theory, dynamical systems, and statistical physics. A graph's sandpile group is part of a larger algebraic structure on the graph, known as its sandpile monoid. Most of the work on sandpiles so far has focused on the sandpile group rather than the sandpile monoid of a graph, and has also assumed the underlying graph to be undirected. A notable exception is the recent work of Babai and Toumpakari, which builds up the theory of sandpile monoids on directed graphs from scratch and provides many connections between the combinatorics of a graph and the algebraic aspects of its sandpile monoid. In this paper we primarily consider sandpile monoids on directed graphs, and we extend the existing theory in four main ways. First, we give a combinatorial classification of the maximal subgroups of a sandpile monoid on a directed graph in terms of the sandpile groups of certain easily-identifiable subgraphs. Second, we point out certain sandpile results for undirected graphs that are really results for sandpile monoids on directed graphs that contain exactly two idempotents. Third, we give a new algebraic constraint that sandpile monoids must satisfy and exhibit two infinite families of monoids that cannot be realized as sandpile monoids on any graph. Finally, we give an explicit combinatorial description of the sandpile group identity for every graph in a family of directed graphs which generalizes the family of (undirected) distance-regular graphs. This family includes many other graphs of interest, including iterated wheels, regular trees, and regular tournaments.
Mechanisms of Allergen-Antibody Interaction of Cockroach Allergen Bla g 2 with Monoclonal Antibodies That Inhibit IgE Antibody Binding
Jill Glesner, Sabina Wünschmann, Mi Li, Alla Gustchina, Alexander Wlodawer, Martin Himly, Martin D. Chapman, Anna Pomés
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022223
Abstract: Background Cockroach allergy is strongly associated with asthma, and involves the production of IgE antibodies against inhaled allergens. Reports of conformational epitopes on inhaled allergens are limited. The conformational epitopes for two specific monoclonal antibodies (mAb) that interfere with IgE antibody binding were identified by X-ray crystallography on opposite sites of the quasi-symmetrical cockroach allergen Bla g 2. Methodology/Principal Findings Mutational analysis of selected residues in both epitopes was performed based on the X-ray crystal structures of the allergen with mAb Fab/Fab′ fragments, to investigate the structural basis of allergen-antibody interactions. The epitopes of Bla g 2 for the mAb 7C11 or 4C3 were mutated, and the mutants were analyzed by SDS-PAGE, circular dichroism, and/or mass spectrometry. Mutants were tested for mAb and IgE antibody binding by ELISA and fluorescent multiplex array. Single or multiple mutations of five residues from both epitopes resulted in almost complete loss of mAb binding, without affecting the overall folding of the allergen. Preventing glycosylation by mutation N268Q reduced IgE binding, indicating a role of carbohydrates in the interaction. Cation-π interactions, as well as electrostatic and hydrophobic interactions, were important for mAb and IgE antibody binding. Quantitative differences in the effects of mutations on IgE antibody binding were observed, suggesting heterogeneity in epitope recognition among cockroach allergic patients. Conclusions/Significance Analysis by site-directed mutagenesis of epitopes identified by X-ray crystallography revealed an overlap between monoclonal and IgE antibody binding sites and provided insight into the B cell repertoire to Bla g 2 and the mechanisms of allergen-antibody recognition, including involvement of carbohydrates.
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