Search results for "Preload"
showing 10 items of 21 documents
A strategy for the finite element modeling of FRP-confined concrete columns subjected to preload
2018
Abstract Compressive behavior of columns strengthened by means of an outer elastic confinement provided e.g. by fiber-reinforced polymer (FRP) jackets has become a main topic in the field of structural retrofitting. In details, the problem of the response assessment of strengthened columns is still under study. Many analytical formulations have been proposed to describe the compressive behavior of confined concrete under both monotonic and cyclic loads. However, the effect of a stress/strain level in the columns already present prior to apply the confinement has been generally neglected until now, also because of the lack of well defined strategies of modeling. In this frame, here, (1) a FE…
Analysis-oriented stress–strain model of CRFP-confined circular concrete columns with applied preload
2018
The compressive behavior of FRP-confined concrete is a current issue in the field of structural retrofitting. The available models well predict the stress–strain behavior under monotonic and cyclic loads. However, in the practical applications, columns that need an increasing of bearing capacity are often strengthened under serviceability load conditions, with a stress and strain state that could change the response of the reinforced systems with respect to the case of the unloaded state. In this paper, the compressive behavior of circular FRP-confined concrete columns with preload is analyzed with the introduction of a modified analysis-oriented model. Differently from the classical formul…
Global End-Diastolic Volume
2021
Global end-diastolic volume (GEDV) as determined at the bedside by the transpulmonary technique is a reliable marker of cardiac preload in critically ill patients. As shown by numerous studies, GEDV is superior to cardiac filling pressures in various settings in anesthesia and intensive care medicine in patients undergoing mechanical ventilation. Furthermore, in scenarios such as open-chest conditions, GEDV should be particularly considered and used for these purposes as dynamic parameters are associated with limitations. Clinical data from patients undergoing elective cardiac and noncardiac surgery showed that goal-directed treatment using GEDV for preload assessment is associated with the…
Acute Hemodynamic Effects of Nicorandil in Coronary Artery Disease
1992
Nicorandil is a potent vasodilator with antianginal and anti-ischemic properties that acts on both the coronary and the peripheral vascular bed. Because of its dual vasodilatory mechanisms mediated by an increase in cyclic GMP similar to that of nitrates and by a selective increase in the K+ conductance of the smooth muscle cell membrane, nicorandil unloads the right and left ventricles at rest and during exercise. Thus, compared with the classic nitrates, nicorandil is a more balanced vasodilator, i.e., it affects not only the venous capacitance vessels (as predominantly affected by nitrates) but also the arterial resistance vessels. In clinical pharmacologic trials, nicorandil has been ad…
Preload loss of abutment screws after dynamic fatigue in single implant-supported restorations. A systematic review
2017
Background To carry out a systematic literature review of the causes of preload loss of the abutment screws, of internal and external connection implants, tightened to different torque values and subjected to cyclic loading. Material and methods A systematic search was conducted in PubMed, EMBASE, and Cochrane Library databases with reference to in vitro studies in which internal and external connection implants were subjected to cyclic loads to determine the degree of loosening of the abutment screws after loading. Results The reviewed studies tested distinct implant connections (mostly externally hexed, and morse taper) subjected to diverse cycles (from 16667 to 1 million), with loads ran…
COMPRESSIVE BEHAVIOR OF CONCRETE COLUMNS AXIALLYLOADED BEFORE CFRP-WRAPPING. REMARKS BY EXPERIMENTALNUMERICAL INVESTIGATION
2018
Strengthening of existing concrete columns with Fiber Reinforced Polymers (FRP) results generally in a satisfactory structural member improvement in terms of load and strain capacity. A reliable prediction of the capacity obtained by these reinforcement strategies requests a proper knowledge of the load-strain response of the confined concrete elements. However, so far, the available design methods and technical codes do not consider the effect of the possible presence of service loads at the moment of application of the reinforcement, and therefore, the compressive behavior of the concrete confined under preload is still unclear. In this paper, the effect of sustained loads on the compress…
Heart in Hyperthyroidism
2019
Hyperthyroidism is a common endocrine disorder that produces important clinical consequences on the cardiovascular system. In overt hyperthyroidism the increase in left ventricular performance is predominantly sustained by an increased preload with enhanced left ventricular diastolic function and reduced systemic vascular resistance. The pattern of cardiovascular abnormalities is similar in subclinical and overt hypothyroidism, suggesting that a lesser degree of thyroid hormone deficiency may also affect the cardiovascular system. Untreated overt and subclinical hypothyroidism can lead to an increased risk of coronary heart disease (CHD), heart failure (HF), and cardiovascular mortality.
Speckle tracking analysis in intensive care unit: A toy or a tool?
2018
The use of conventional echocardiography in the intensive care unit (ICU) is today established to assess left and right ventricular systolic function, for preload determination and procedural guidance. Next step in ICU echocardiography could be the use of novel ultrasound techniques such as strain echocardiography to assist in the management of patients with acute coronary syndrome, heart failure, or pulmonary embolism. This review has gathered the available evidence supporting the incremental value of strain in the diagnostic workup of cardiac diseases treated in ICU.
Role of Nitrates for the Therapy of Coronary Artery Disease Patients in the Years beyond 2000
1999
Vasodilator therapy with nitrates has been used for almost a century to bring relief to patients suffering from angina. The acute anti-ischemic effects of nitro-vasodilators for the treatment and prevention of anginal attacks is unquestioned. In addition, nitrates are administered in order to reduce symptomatic and silent ischemic episodes, in patients with proven coronary heart disease who exert ST segment alterations on Holter monitoring. The reduction in total ischemic burden may result in an improved prognosis with regard to infarct prevention and possible prevention of deterioration of left ventricular function due to repetitive episodes of myocardial ischemia. In patients with unstabl…
Arterial Load and Norepinephrine Are Associated With the Response of the Cardiovascular System to Fluid Expansion
2021
BackgroundFluid responsiveness has been extensively studied by using the preload prism. The arterial load might be a factor modulating the fluid responsiveness. The norepinephrine (NE) administration increases the arterial load and modifies the vascular properties. The objective of the present study was to determine the relationship between fluid responsiveness, preload, arterial load, and NE use. We hypothesized that as a preload/arterial load, NE use may affect fluid responsiveness.MethodsThe retrospective multicentered analysis of the pooled data from 446 patients monitored using the transpulmonary thermodilution before and after fluid expansion (FE) was performed. FE was standardized be…