Stability of Runge–Kutta–Nyström methods

AbstractIn this paper, a general and detailed study of linear stability of Runge–Kutta–Nyström (RKN) methods is given. In the case that arbitrarily stiff problems are integrated, we establish a condition that RKN methods must satisfy so that a uniform bound for stability can be achieved. This condition is not satisfied by any method in the literature. Therefore, a stable method is constructed and some numerical comparisons are made

Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.

BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden

Excessive dynamic airway collapse in a small cohort of chronic obstructive pulmonary disease patients

INTRODUCTION: The prevalence of EDAC (Excessive Dynamic Airway Collapse) has not been studied specifically in patients with chronic obstructive pulmonary disease (COPD). OBJECTIVE: The aim of this study was to investigate the prevalence of EDAC in COPD and to determine whether there are clinical factors or functional variables that could influence the degree of expiratory collapse of central airways. METHODS: Prospective observational study of a group of patients with COPD. The degree of tracheobronchial collapse was evaluated by low-dose dynamic airway computed tomography (CT). We recorded clinical and pulmonary function tests data, quality of life and BODE index. RESULTS: This study included 53 patients with COPD, 46 (87%) males, mean age 65 (SD, 9) years. The percentage of collapse at each anatomic level was as follows: Aortic arch, 16.1% (SD, 13.6%); carina, 19.4% (SD, 15.9%); and bronchus intermedius, 21.7% (SD, 16.1%). At the point of maximal collapse, the percentage of collapse was 26.8% (SD, 16%). EDAC was demonstrated at any of the three anatomical points in five patients, corresponding to 9.4% (95% CI, 3.1% to 20.6%) of the sample and affecting the three anatomical points in only two cases. A statistically significant correlation was only found with the total lung capacity (TLC). CONCLUSIONS: The prevalence of EDAC observed in a sample of patients with different levels of COPD severity is low. The degree of dynamic central airway collapse was not related to the patient′s epidemiological or clinical features, and did not affect lung function, symptoms, capacity for effort, or quality of life