BackgroundSevere exacerbations and mortality are major outcomes in COPD, and risk factors for these events are actively searched for. Several predictors of mortality have been identified in COPD. The inspiratory capacity/total lung capacity (IC/TLC) ratio has been shown to be a strong predictor of all cause and respiratory mortality in patients with COPD. The major objectives of this study were to analyze which clinical parameters, including lung volumes, were the best predictors of the 5-year cumulative risk of hospital admissions or death and the 5-year risk of exacerbations, in stable COPD patients.MethodsThis study retrospectively reviewed data from 98 stable COPD patients, consecutively recruited in 2012. Forced expiratory volume in 1 s (FEV1), modified Medical Research Council dyspnea scale, exacerbation history (ExH), Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2011 groups, and lung volumes were reviewed. Five years later, this population was evaluated for cumulative exacerbations, hospital admissions, and mortality. All the population, and GOLD group D separately, were analyzed.ResultsThe cumulative 5-year combined risk of hospital admission or death was significantly predicted by the ExH and the IC/TLC ratio. Analyzing separately group D, FEV1 was the only predictor of this outcome. The frequency of exacerbations in the previous year was the best predictor of future cumulative 5-year risk of subsequent exacerbations, both for the total population and the GOLD D group.ConclusionExH and IC/TLC ratio were the best predictors of the most severe outcomes in COPD (admissions or mortality), independently of COPD severity. FEV1 was the only predictor of the cumulative 5-year combined risk of hospital admission or death in the GOLD D group. ExH was the best predictor of 5-year cumulative future risk of exacerbations. Besides FEV1 and ExH, the IC/TLC ratio can be a useful predictor of severe outcomes in COPD.
This paper describes a unified variational theory for design sensitivity analysis of nonlinear dynamic response of structural and mechanical systems for shape, nonshape, material and mechanical properties selection, as well as control problems. The concept of an adjoint system, the principle of virtual work and a Lagrangian-Eulerian formulation to describe the deformations and the design variations are used to develop a unified view point. A general formula for design sensitivity analysis is derived and interpreted for usual performance functionals. Analytical examples are utilized to demonstrate the use of the theory and give insights for application to more complex problems that must be treated numerically.
NomenclatureThe notation for analysis of nonlinear structural mechanics problems tends to be tedious and complex. To facilitate reading of the paper, the nomenclature used in the development of various concepts is summarized here. Bold faced letters represent tensors or matrices, and a %" between two letters implies direct tensor product.
This paper describes a unified variational theory of design sensitivity analysis of linear and nonlinear structures for shape, nonshape, and material selection problems. The concepts of reference volume and adjoint structure are used to develop the unified viewpoint. A general formula for design sensitivity analysis is derived. Several analytical linear and nonlinear examples are used to interpret various terms of the formula and demonstrate its use. Such analytical examples give insight into the application of the general formula to more complex problems that must be treated numerically. Adjoint state fields are also interpreted as sensitivities for the functional related to the primary structure.
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