Search results for "Surrogate"
showing 10 items of 145 documents
Subclinical atherosclerosis and fetuin-A plasma levels in essential hypertensive patients
2012
The intima-media thickness (IMT) is considered as a surrogate marker for atherosclerotic disease. The aim of this study was to analyze the relationship of carotid IMT with fetuin-A in patients with essential hypertension (EH) and normal renal function. The plasma levels of fetuin-A, interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and the biomarker of oxidative stress 8-iso-PGF2alpha were assayed in samples from 105 untreated EH patients. Carotid IMT measurements were also performed. EH was studied overall and after dividing in EH with IMT ≥ and 0.9 mm (AUC (area under the curve) 0.738, P<0.0001). Our results suggest that in EH, fetuin-A is associated with the IMT independently of oxid…
Linear and non-linear brain-heart and brain-brain interactions during sleep.
2015
In this study, the physiological networks underlying the joint modulation of the parasympathetic component of heart rate variability (HRV) and of the different electroencephalographic (EEG) rhythms during sleep were assessed using two popular measures of directed interaction in multivariate time series, namely Granger causality (GC) and transfer entropy (TE). Time series representative of cardiac and brain activities were obtained in 10 young healthy subjects as the normalized high frequency (HF) component of HRV and EEG power in the δ, θ, α, Ï, and β bands, measured during the whole duration of sleep. The magnitude and statistical significance of GC and TE were evaluated between each …
Intensive care unit strain should not rush physicians into making inappropriate decisions, but merely reduce the time to the right decisions being ma…
2016
The effect of capacity strain in an ICU on the timing of end-of-life decision-making is unknown. We sought to determine how changes in strain impact timing of new do-not-resuscitate (DNR) orders and of death.Retrospective cohort study of 9891 patients dying in the hospital following an ICU stay ≥72 h in Project IMPACT, 2001-2008. We examined the effect of ICU capacity strain (measured by standardized census, proportion of new admissions, and average patient acuity) on time to initiation of DNR orders and time to death for all ICU decedents using fixed-effects linear regression.Increases in strain were associated with shorter time to DNR for patients with limitations in therapy (predicted ti…
Usefulness of delta troponin for diagnosis and prognosis assessment of non-ST-segment elevation acute chest pain.
2014
The additional diagnostic and prognostic information provided by delta high-sensitivity troponin T (hs-cTnT) in patients with acute chest pain and hs-cTnT elevation remains unclear.The study group consisted of 601 patients presenting at the emergency department with non-ST-segment elevation acute chest pain and hs-cTnT elevation after two determinations (admission and within the first six hours). Maximum hs-cTnT and delta hs-cTnT (absolute or percentage change between the two measurements) were considered. Cutoff values were optimized using the quartile distribution for the endpoints. The endpoints were diagnostic (significant stenosis in the coronary angiogram) and prognostic (death or rec…
Predictive biomarkers for death and rehospitalization in comorbid frail elderly heart failure patients.
2018
Background Heart failure (HF) is associated with a high rate of readmissions within 30 days post-discharge and in the following year, especially in frail elderly patients. Biomarker data are scarce in this high-risk population. This study assessed the value of early post-discharge circulating levels of ST2, NT-proBNP, CA125, and hs-TnI for predicting 30-day and 1-year outcomes in comorbid frail elderly patients with HF with mainly preserved ejection fraction (HFpEF). Methods Blood samples were obtained at the first visit shortly after discharge (4.9 ± 2 days). The primary endpoint was the composite of all-cause mortality or HF-related rehospitalization at 30 days and at 1 year. All-cause mo…
Continuous ambulatory peritoneal dialysis as a therapeutic alternative in patients with advanced congestive heart failure.
2012
Aims Continuous ambulatory peritoneal dialysis (CAPD) has been proposed as an additional therapeutic resource for patients with advanced congestive heart failure (CHF). The objective of this study was to determine the therapeutic role of CAPD, in terms of surrogate endpoints, in the management of patients with advanced CHF and renal dysfunction. A total of 57 candidates with New York Heart Association (NYHA) class III/IV CHF, renal dysfunction (glomerular filtration rate , 60 mL/min/1.73 m 2 ), persistent fluid congestion despite loop diuretic treatment, and at least two previous hospitalizations for acute heart failure (AHF) were invited to be included in the CAPD programme; however, 25 pa…
Constraint handling in efficient global optimization
2017
Real-world optimization problems are often subject to several constraints which are expensive to evaluate in terms of cost or time. Although a lot of effort is devoted to make use of surrogate models for expensive optimization tasks, not many strong surrogate-assisted algorithms can address the challenging constrained problems. Efficient Global Optimization (EGO) is a Kriging-based surrogate-assisted algorithm. It was originally proposed to address unconstrained problems and later was modified to solve constrained problems. However, these type of algorithms still suffer from several issues, mainly: (1) early stagnation, (2) problems with multiple active constraints and (3) frequent crashes.…
Conflict resolution in the multi-stakeholder stepped spillway design under uncertainty by machine learning techniques
2021
Abstract The optimal spillway design is of great significance since these structures can reduce erosion downstream of the dams. This study proposes a risk-based optimization framework for a stepped spillway to achieve an economical design scenario with the minimum loss in hydraulic performance. Accordingly, the stepped spillway was simulated in the FLOW-3D® model, and the validated model was repeatedly performed for various geometric states. The results were used to form a Multilayer Perceptron artificial neural network (MLP-ANN) surrogate model. Then, a risk-based optimization model was formed by coupling the MLP-ANN and NSGA-II. The concept of conditional value at risk (CVaR) was utilized…
Towards Better Integration of Surrogate Models and Optimizers
2019
Surrogate-Assisted Evolutionary Algorithms (SAEAs) have been proven to be very effective in solving (synthetic and real-world) computationally expensive optimization problems with a limited number of function evaluations. The two main components of SAEAs are: the surrogate model and the evolutionary optimizer, both of which use parameters to control their respective behavior. These parameters are likely to interact closely, and hence the exploitation of any such relationships may lead to the design of an enhanced SAEA. In this chapter, as a first step, we focus on Kriging and the Efficient Global Optimization (EGO) framework. We discuss potentially profitable ways of a better integration of…
Parametric and nonparametric methods to generate time-varying surrogate data.
2009
We present both nonparametric and parametric approaches to generating time-varying surrogate data. Nonparametric and parametric approaches are based on the use of the short-time Fourier transform and a time-varying autoregressive model, respectively. Time-varying surrogate data (TVSD) can be used to determine the statistical significance of the linear and nonlinear coherence function estimates. Two advantages of the TVSD are that it keeps one from having to make an arbitrary decision about the significance of the coherence value, and it properly takes into account statistical significance levels, which may change with time. Our simulation examples and experimental results on blood pressure …