56 research outputs found
Paging on Complex Architectures
Get PDFAdvances in technology allow to build computer systems of ever increasing performances and capabilities. However, the effective use of such computational resources is often made difficult by the complexity of the system itself. Crucial to the performance of a computing device is the orchestration of the flow of data across the memory hierarchy. Specifically, given a fast but small memory (a cache) through which all the data that have to be processed must pass, it is necessary to establish a set of rules, then implemented by an algorithm, that define which data has to be evicted from such a memory to make room for new incoming data. The goal is that of minimizing the number of times that requested data is outside the cache (faults), since fetching data from farther levels of the memory hierarchy incurs high costs, in terms of time and also of energy. This thesis studies two generalizations of this problem, known as the paging problem. This problem is intrinsically online, as future data requests issued by a computer program are typically unknown.
Motivated by the recent diffusion of multi-threaded and multi-core
architectures, whereby several threads or processes can be executed
simultaneously, and/or there are several processing units, and by the recent and rapidly growing interest in reducing power consumptions of computer systems, in the first part of the thesis we study a variation of paging which rewards the efficient usage of memory resources. In this problem the goal is that of minimizing a combination of both the number of faults and the cache occupancy of the process' data in fast memory. The main results of this part are two: the first is an impossibility result that indicates that, roughly speaking, online algorithms cannot compete in practice with algorithms that know
in advance all the data requests issued by the process; the second is the design of an online algorithm that has almost the best performance among all the possible online algorithms.
In the second part of the thesis we concentrate on the management of a cache shared among several concurrent processes. As outlined above, this has direct application in multi-threaded or multi-core architectures. In this problem the fast memory has to service a sequence of requests which is the interleaving of the requests issued by t different processes. Through its replacement decisions, the algorithm dynamically allocates the cache space among the processes, and this clearly impacts their progress. The main goal here is to minimize the time needed to complete the service of all the request sequences. We show tight lower and upper bounds on the performance of online algorithms for several variants of the problem
The other side of novel coronavirus outbreak: Fear of performing cardiopulmonary resuscitation
No full textEmergency calls as an early indicator of intensive care unit demand for coronavirus disease 2019
No full textMobile phone systems to alert citizens as first responders and to locate automated external defibrillators: A European survey
No full textRandomised trials of temperature management in cardiac arrest: Are we observing the Zeno’s paradox of the Tortoise and Achilles?
No full textCardiac arrest reported in newspapers: A new, yet missed, opportunity to increase cardiopulmonary resuscitation awareness
No full textNon-Invasive Ventilation in the Prehospital Emergency Setting: A Systematic Review and Meta-Analysis
No full textIntroduction: Noninvasive ventilation is a well-established treatment for acute respiratory failure, being increasingly applied in the prehospital setting. This systematic review and meta-analysis aims to investigate whether early prehospital initiation of noninvasive ventilation reduces mortality compared to standard oxygen therapy. Methods: We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials from inception to February 7th, 2022, for studies comparing prehospital noninvasive ventilation performed by emergency medical services versus standard oxygen therapy in patients with acute respiratory failure. The primary outcome was mortality at the longest follow-up available. Results: We included ten randomized studies and two quasi-randomized studies for a total of 1485 patients. Prehospital treatment with noninvasive ventilation compared with standard oxygen therapy did not significantly reduce mortality at the longest follow-up available (107/810 [13%] vs 114/772 [15%]; RR = 0.89; 95% CI, 0.70–1.13; P = 0.34; I2=24%). The endotracheal intubation rate was reduced when receiving prehospital noninvasive ventilation (38/776 [4.9%] vs 81/743 [11%]; RR = 0.44; 95% CI, 0.31–0.63; P < 0.001; I2=0%; number needed to treat 17). The intensive care admission rate (114/532 [21%] vs 129/507 [25%]; RR = 0.85; 95% CI, 0.69–1.04; P = 0.11; I2=0%) and length of hospital stay (mean difference=-1.29 days; 95% CI, −3.35–0.77; P = 0.21; I2=82%) were similar between groups. Conclusions: Adults with acute respiratory failure treated in the prehospital setting with noninvasive ventilation had a lower risk of intubation than those managed with standard oxygen therapy, with similar risk of death, intensive care admission, and length of hospital stay. Review registration: PROSPERO CRD42021284947
Effects of COVID-19 pandemic on out-of-hospital cardiac arrests: A systematic review
No full textIntroduction: In addition to the directly attributed mortality, COVID-19 is also likely to increase mortality indirectly. In this systematic review, we investigate the direct and indirect effects of COVID-19 on out-of-hospital cardiac arrests. Methods: We searched PubMed, BioMedCentral, Embase and the Cochrane Central Register of Controlled Trials for studies comparing out-of-hospital cardiac arrests occurring during the pandemic and a non-pandemic period. Risk of bias was assessed with the ROBINS-I tool. The primary endpoint was return of spontaneous circulation. Secondary endpoints were bystander-initiated cardiopulmonary resuscitation, survival to hospital discharge, and survival with favourable neurological outcome. Results: We identified six studies. In two studies, rates of return of spontaneous circulation and survival to hospital discharge decreased significantly during the pandemic. Especially in Europe, bystander-witnessed cases, bystander-initiated cardiopulmonary resuscitation and resuscitation attempted by emergency medical services were reduced during the pandemic. Also, ambulance response times were significantly delayed across all studies and patients presenting with non-shockable rhythms increased in two studies. In 2020, 3.9–5.9% of tested patients were SARS-CoV-2 positive and 4.8–26% had suggestive symptoms (fever and cough or dyspnoea). Conclusions: Out-of-hospital cardiac arrests had worse short-term outcomes during the pandemic than a non-pandemic period suggesting direct effects of COVID-19 infection and indirect effects from lockdown and disruption of healthcare systems. Patients at high risk of deterioration should be identified outside the hospital to promptly initiate treatment and reduce fatalities. Study registration PROSPERO CRD42020195794
Enhancing citizens response to out-of-hospital cardiac arrest: A systematic review of mobile-phone systems to alert citizens as first responders
No full textIntroduction: Involving laypersons in response to out-of-hospital cardiac arrest through mobile-phone technology is becoming widespread in numerous countries, and different solutions were developed. We performed a systematic review on the impact of alerting citizens as first responders and to provide an overview of different strategies and technologies used. Methods: We searched electronic databases up to October 2019. Eligible studies described systems to alert citizens first responders to out-of-hospital cardiac arrest through text messages or apps. We analyzed the implementation and performance of these systems and their impact on patients’ outcomes. Results: We included 28 manuscripts describing 12 different systems. The first text message system was implemented in 2006 and the first app in 2010. First responders accepted to intervene in median (interquartile) 28.7% (27–29%) of alerts and reached the scene after 4.6 (4.4–5.5) minutes for performing CPR. First responders arrived before ambulance, started CPR and attached a defibrillator in 47% (34–58%), 24% (23–27%) and 9% (6–14%) of cases, respectively. Pooled analysis showed that first responders activation increased layperson-CPR rates (1463/2292 [63.8%] in the intervention group vs. 1094/1989 [55.0%] in the control group; OR = 1.70; 95% CI, 1.11–2.60; p = 0.01) and survival to hospital discharge or at 30 days (327/2273 [14.4%] vs. 184/1955 [9.4%]; OR = 1.51; 95% CI, 1.24–1.84; p < 0.001). Conclusions: Alerting citizens as first responders in case of out-of-hospital cardiac arrest may reduce the intervention-free time and improve patients’ outcomes
Extracorporeal cardiopulmonary resuscitation for out-of-hospital cardiac arrest: A systematic review and meta-analysis of randomized and propensity score-matched
No full textBackground: In selected patients with refractory out-of-hospital cardiac arrest, extracorporeal cardiopulmonary resuscitation represents a promising approach when conventional cardiopulmonary resuscitation fails to achieve return of spontaneous circulation. This systematic review and meta-analysis aimed to compare extracorporeal cardiopulmonary resuscitation to conventional cardiopulmonary resuscitation. Methods: We searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials up to November 28, 2021, for randomized trials and observational studies reporting propensity score-matched data and comparing adults with out-of-hospital cardiac arrest treated with extracorporeal cardiopulmonary resuscitation with those treated with conventional cardiopulmonary resuscitation. The primary outcome was survival with favorable neurological outcome at the longest follow-up available. Secondary outcomes were survival at the longest follow-up available and survival at hospital discharge/30 days. Results: We included six studies, two randomized and four propensity score-matched studies. Patients treated with extracorporeal cardiopulmonary resuscitation had higher rates of survival with favorable neurological outcome (81/584 [14%] vs. 46/593 [7.8%]; OR = 2.11; 95% CI, 1.41–3.15; p < 0.001, number needed to treat 16) and of survival (131/584 [22%] vs. 102/593 [17%]; OR = 1.40; 95% CI, 1.05–1.87; p = 0.02) at the longest follow-up available compared with conventional cardiopulmonary resuscitation. Survival at hospital discharge/30 days was similar between the two groups (142/584 [24%] vs. 122/593 [21%]; OR = 1.26; 95% CI, 0.95–1.66; p = 0.10). Conclusions: Evidence from randomized trials and propensity score-matched studies suggests increased survival and favorable neurological outcome in patients with refractory out-of-hospital cardiac arrest treated with extracorporeal cardiopulmonary resuscitation. Large, multicentre randomized studies are still ongoing to confirm these findings
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