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Failure Model (failure + model)
Selected AbstractsEvaluation of 6 Prognostic Models Used to Calculate Mortality Rates in Elderly Heart Failure Patients With a Fatal Heart Failure AdmissionCONGESTIVE HEART FAILURE, Issue 5 2010Andria L. Nutter The objective was to evaluate 6 commonly used heart failure (HF) prognostic models in an elderly, fatal HF population. Predictive models have been established to quantify risk among HF patients. The validation of these models has not been adequately studied, especially in an elderly cohort. Applying a single-center, retrospective study of serially admitted HF patients who died while in the hospital or within 30 days of discharge, the authors evaluated 6 prognostic models: the Seattle Heart Failure Model (SHFM), Heywood's model, Classification and Regression Tree (CART) Analysis, the Heart Failure Survival Score (HFSS), Heart Failure Risk Scoring System, and Pocock's score. Eighty patients were included (mean age, 82.7 ± 8.2 years). Twenty-three patients (28.75%) died in the hospital. The remainder died within 30 days of discharge. The models' predictions varied considerably from one another and underestimated the patients' actual mortality. This study demonstrates that these models underestimate the mortality risk in an elderly cohort at or approaching the end of life. Moreover, the predictions made by each model vary greatly from one another. Many of the models used were not intended for calculation during hospitalization. Development of improved models for the range of patients with HF syndromes is needed. Congest Heart Fail. 2010;16:196,201. © 2010 Wiley Periodicals, Inc. [source] Intrahepatic amino acid and glucose metabolism in a D -galactosamine,induced rat liver failure modelHEPATOLOGY, Issue 2 2001Kosuke Arai A better understanding of the hepatic metabolic pathways affected by fulminant hepatic failure (FHF) would help develop nutritional support and other nonsurgical medical therapies for FHF. We used an isolated perfused liver system in combination with a mass-balance model of hepatic intermediary metabolism to generate a comprehensive map of metabolic alterations in the liver in FHF. To induce FHF, rats were fasted for 36 hours, during which they received 2 D -galactosamine injections. The livers were then perfused for 60 minutes via the portal vein with amino acid,supplemented Eagle minimal essential medium containing 3% wt/vol bovine serum albumin and oxygenated with 95% O2/5% CO2. Control rats were fasted for 36 hours with no other treatment before perfusion. FHF rat livers exhibited reduced amino acid uptake, a switch from gluconeogenesis to glycolysis, and a decrease in urea synthesis, but no change in ammonia consumption compared with normal fasted rat livers. Mass-balance analysis showed that hepatic glucose synthesis was inhibited as a result of a reduction in amino acid entry into the tricarboxylic acid cycle by anaplerosis. Furthermore, FHF inhibited intrahepatic aspartate synthesis, which resulted in a 50% reduction in urea cycle flux. Urea synthesis by conversion of exogenous arginine to ornithine was unchanged. Ammonia removal was quantitatively maintained by glutamine synthesis from glutamate and a decrease in the conversion of glutamate to ,-ketoglutarate. Mass-balance analysis of hepatic metabolism will be useful in characterizing changes during FHF, and in elucidating the effects of nutritional supplements and other treatments on hepatic function. [source] Adversarial models for priority-based networks,NETWORKS: AN INTERNATIONAL JOURNAL, Issue 1 2005C. Ąlvarez Abstract In this article, we propose several variations of the adversarial queueing model and address stability issues of networks and protocols in those proposed models. The first such variation is the priority model, which is directed at static network topologies and takes into account the case in which packets can have different priorities. Those priorities are assigned by an adversary at injection time. A second variation, the variable priority model, is an extension of the priority model in which the adversary may dynamically change the priority of packets at each time step. Two more variations, namely the failure model and the reliable model, are proposed to cope with dynamic networks. In the failure and reliable models the adversary controls, under different constraints, the failures that the links of the topology might suffer. Concerning stability of networks in the proposed adversarial models, we show that the set of universally stable networks in the adversarial model remains the same in the priority, variable priority, failure, and reliable models. From the point of view of protocols (or queueing policies), we show that several protocols that are universally stable in the adversarial queueing model remain so in the priority, failure, and reliable models. However, we show that the longest-in-system (LIS) protocol, which is universally stable in the adversarial queueing model, is not universally stable in any of the other models we propose. Moreover, we show that no queueing policy is universally stable in the variable priority model. Finally, we analyze the problem of deciding stability of a given network under a fixed protocol. We provide a characterization of the networks that are stable under first-in-first-out (FIFO) and LIS in the failure model (and therefore in the reliable and priority models). This characterization allows us to show that the stability problem under FIFO and LIS in the failure model can be solved in polynomial time. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 45(1), 23,35 2005 [source] A New Approach to Assist Postoperative Heart Failure in an Animal Model: Juxta-Aortic CounterpulsationARTIFICIAL ORGANS, Issue 10 2002Edmundo I. Cabrera Fischer Abstract: Aortic counterpulsation is a useful technique frequently used in postcardiotomy heart failure. An acute heart failure model in open chest sheep was chosen to evaluate hemodynamic improvement with a counterpulsation balloon pump in juxta-aortic position. This was achieved with a manufactured Dacron prosthesis and a balloon pump placed between the prosthesis and the aorta. Juxta-aortic balloon pump counterpulsation in acute experimental heart failure resulted in a significant improvement of hemodynamic parameters: increase of cardiac output (from 0.86 ± 0.04 to 1.29 ± 0.09 L/min, p < 0.05) and cardiac index (from 0.03 ± 0.01 to 0.04 ± 0.01 L/min per kg, p < 0.05), and decrease of systemic vascular resistance (from 89.76 ± 6.69 to 66.56 ± 6.02 mm Hg/L per min, p < 0.05). The extent of aortic diastolic pressure change evaluated through the diastolic and systolic areas beneath the aortic pressure curve (DABAC/SABAC) index before cardiac failure induction showed a significant increase compared with unassisted values (from 0.81 ± 0.10 to 1.12 ± 0.09, p < 0.05). Assisted values of DABAC/SABAC index after heart failure induction also showed a significant increase compared with unassisted values (from 0.78 ± 0.21 to 1.17 ± 0.38, p < 0.05). Treatment of experimental acute heart failure by juxta-aortic balloon pump counterpulsation allows an effective hemodynamic improvement in open chest sheep. [source] Cerebral Tissue Oxygen Saturation During Percutaneous Cardiopulmonary Support in a Canine Model of Respiratory FailureARTIFICIAL ORGANS, Issue 8 2000Hideichi Wada Abstract: Percutaneous cardiopulmonary support (PCPS) has come to be applied for cardiopulmonary resuscitation and in the management of severe respiratory failure as well as severe heart failure. We investigated cerebral tissue oxygen saturation during PCPS in a canine model of respiratory failure using near-infrared spectroscopy. Animals were mechanically ventilated with 10% oxygen to make a respiratory failure model. Perfusion with PCPS was performed via the left femoral artery and switched to that via the right axillary artery. Cerebral tissue oxygen saturation was 54.2 ± 3.4% during PCPS via the femoral artery and was 82.3 ± 4.6% during PCPS via the axillary artery (p = 0.001). Hepatic tissue oxygen saturation was not significantly different. LV dP/dt max increased significantly after switching to the axillary blood supply (p = 0.001). Conventional PCPS may not have the capability of supporting cerebral circulation under severe respiratory failure without organic heart disease. [source] | ||||||||||