How to handle mortality when investigating length of hospital stay and time to clinical stability

<p>Abstract</p> <p>Background</p> <p>Hospital length of stay (LOS) and time for a patient to reach clinical stability (TCS) have increasingly become important outcomes when investigating ways in which to combat Community Acquired Pneumonia (CAP). Difficulties arise when deciding how to handle in-hospital mortality. Ad-hoc approaches that are commonly used to handle time to event outcomes with mortality can give disparate results and provide conflicting conclusions based on the same data. To ensure compatibility among studies investigating these outcomes, this type of data should be handled in a consistent and appropriate fashion.</p> <p>Methods</p> <p>Using both simulated data and data from the international Community Acquired Pneumonia Organization (CAPO) database, we evaluate two ad-hoc approaches for handling mortality when estimating the probability of hospital discharge and clinical stability: 1) restricting analysis to those patients who lived, and 2) assigning individuals who die the "worst" outcome (right-censoring them at the longest recorded LOS or TCS). Estimated probability distributions based on these approaches are compared with right-censoring the individuals who died at time of death (the complement of the Kaplan-Meier (KM) estimator), and treating death as a competing risk (the cumulative incidence estimator). Tests for differences in probability distributions based on the four methods are also contrasted.</p> <p>Results</p> <p>The two ad-hoc approaches give different estimates of the probability of discharge and clinical stability. Analysis restricted to patients who survived is conceptually problematic, as estimation is conditioned on events that happen <it>at a future time</it>. Estimation based on assigning those patients who died the worst outcome (longest LOS and TCS) coincides with the complement of the KM estimator based on the subdistribution hazard, which has been previously shown to be equivalent to the cumulative incidence estimator. However, in either case the time to in-hospital mortality is ignored, preventing simultaneous assessment of patient mortality in addition to LOS and/or TCS. The power to detect differences in underlying hazards of discharge between patient populations differs for test statistics based on the four approaches, and depends on the underlying hazard ratio of mortality between the patient groups.</p> <p>Conclusions</p> <p>Treating death as a competing risk gives estimators which address the clinical questions of interest, and allows for simultaneous modelling of both in-hospital mortality and TCS / LOS. This article advocates treating mortality as a competing risk when investigating other time related outcomes.</p

Metal early diagenesis and pollution in the tidal flats of the Marennes Oleron Bay: Application of metal sequential extraction

The study of metal partition patterns in the tidal flats of the Marennes Oleron Bay shows that the metal partition patterns in the superficial sediments indicate that the major part of the mobile fraction of metals is associated with Fe-Mn oxides. The metal fractions associated with organic matter are relatively small. As depth increases, the decrease of metal reducible fraction is evidence of oxide dissolution under reducing conditions. The increase of metal sulfide-organic fraction with an increasing depth of burial, supports the idea of metal sulfide formations. Calculations show that the total sulfur in the sediments is in excess with respect to iron extracted by the hydrogen peroxide treatment. This assumes the existence of Fe fraction as FeS sub(2) and FeS. Mn enrichment in the surface sediments is the result of Mn dissolution, upward migration, and precipitation. Nevertheless, Pb enrichment seems to be the result of high Pb anthropogenic flux

Near-Optimal Switching Strategies for a Tandem Queue

textabstractMotivated by various applications in logistics, road traffic and production management, we investigate two versions of a tandem queueing model in which the service rate of the first queue can be controlled. The objective is to keep the mean number of jobs in the second queue as low as possible, without compromising the total system delay (i.e. avoiding starvation of the second queue). The balance between these objectives is governed by a linear cost function of the queue lengths. In the first model, the server in the first queue can be either switched on or off, depending on the queue lengths of both queues. This model has been studied extensively in the literature. Obtaining the optimal control is known to be computationally intensive and time consuming.We are particularly interested in the scenario that the first queue can operate at larger service speed than the second queue. This scenario has received less attention in literature. We propose an approximation using an efficient mathematical analysis of a near-optimal threshold policy based on a matrix-geometric solution of the stationary probabilities that enables us to compute the relevant stationary measures more efficiently and determine an optimal choice for the threshold value. In some of our target applications, it is more realistic to see the first queue as a (controllable) batch-server system. We follow a similar approach as for the first model and obtain the structure of the optimal policy as well as an efficiently computable near-optimal threshold policy. We illustrate the appropriateness of our approximations using simulations of both models

A Heptanuclear Copper Iodide Nanocluster

International audienc

Exploring a byzantine crypt through a highresolution texture mapped 3D model: combining range data and photogrammetry

In recent years, high-resolution recording of heritage sites has stimulated a lot of research in fields like photogrammetry, computer vision, and computer graphics. Numerous algorithms and methodologies have been proposed in the literature. In practice, what a 3D photographer needs is a commercially available solution to this so-called as-built documentation. In this paper, we present an effective approach for photo-realistic 3D model building from the combination of photogrammetry and 3D range data. The method is applied to the virtualization of a Byzantine Crypt where geometrically correct texture mapping is essential to render the environment accurately in order to produce enticing virtual visits, apply virtual restoration techniques on the frescoes and remove architectural elements that have been added over the years so that the site can then be viewed in the correct historical context. A movie entitled &quot;CARPINIANA&quot; was created in order to demonstrate the results

Virtualizing a Byzantine Crypt by Combining High-resolution Textures with Laser Scanner 3D Data

In recent years, high-resolution recording of heritage sites has stimulated a lot of research in fields like photogrammetry, computer vision, and computer graphics. Numerous algorithms and methodologies have been proposed in the literature fo

Maternal overnutrition programs changes in the expression of skeletal muscle genes that are associated with insulin resistance and defects of oxidative phosphorylation in adult male rat offspring.

Children of obese mothers have increased risk of metabolic syndrome as adults. Here we report the effects of a high-fat diet in the absence of maternal obesity at conception on skeletal muscle metabolic and transcriptional profiles of adult male offspring. Female Sprague Dawley rats were fed a diet rich in saturated fat and sucrose [high-fat diet (HFD): 23.5% total fat, 9.83% saturated fat, 20% sucrose wt:wt] or a normal control diet [(CD) 7% total fat, 0.5% saturated fat, 10% sucrose wt:wt] for the 3 wk prior to mating and throughout pregnancy and lactation. Maternal weights were not different at conception; however, HFD-fed dams were 22% heavier than controls during pregnancy. On a normal diet, the male offspring of HFD-fed dams were not heavier than controls but demonstrated features of insulin resistance, including elevated plasma insulin concentration [40.1 &plusmn; 2.5 (CD) vs 56.2 &plusmn; 6.1 (HFD) mU/L; P = 0.023]. Next-generation mRNA sequencing was used to identify differentially expressed genes in the offspring soleus muscle, and gene set enrichment analysis (GSEA) was used to detect coordinated changes that are characteristic of a biological function. GSEA identified 15 upregulated pathways, including cytokine signaling (P &lt; 0.005), starch and sucrose metabolism (P &lt; 0.017), inflammatory response (P &lt; 0.024), and cytokine-cytokine receptor interaction (P &lt; 0.037). A further 8 pathways were downregulated, including oxidative phosphorylation (P &lt; 0.004), mitochondrial matrix (P &lt; 0.006), and electron transport/uncoupling (P &lt; 0.022). Phosphorylation of the insulin signaling protein kinase B was reduced [2.86 &plusmn; 0.63 (CD) vs 1.02 &plusmn; 0.27 (HFD); P = 0.027] and mitochondrial complexes I, II, and V protein were downregulated by 50-68% (P &lt; 0.005). On a normal diet, the male offspring of HFD-fed dams did not become obese adults but developed insulin resistance, with transcriptional evidence of muscle cytokine activation, inflammation, and mitochondrial dysfunction. These data indicate that maternal overnutrition, even in the absence of prepregnancy obesity, can promote metabolic dysregulation and predispose offspring to type 2 diabetes