Obtenção e Caracterização de Nanopartículas Magnéticas Inseridas em Materiais Carbonosos Porosos a partir da Decomposição do Pentacarbonil Ferro.

Este trabalho é dedicado à síntese e caracterização de nanopartículas de óxidos de ferro dispersas na estrutura porosa de um carvão ativado, originando nanocompósitos com propriedades magnéticas. As amostras foram preparadas a partir da mistura do organometálico pentacarbonil ferro com o carvão ativado, em diferentes proporções e sob as atmosferas ambiente e de argônio. As técnicas experimentais utilizadas para a caracterização foram: espectroscopia Mössbauer, difração de raios-X convencional e com luz síncrotron , espectroscopia de fotoelétrons excitados por raios-X, microscopia eletrônica de varredura, análise textural por adsorção de nitrogênio, medidas de propriedades magnéticas, análise elementar e termogravimetria. Os resultados mostraram que os teores de ferro nas amostras como preparadas atingiram valores de até 33 % em massa, aproximadamente. As nanopartículas foram identificadas como óxidos de ferro dispersos de forma homogênea no carvão ativado, com tamanho médio de cristalito na faixa 4-6nm e apresentando comportamento superparamagnético em temperatura ambiente. As amostras preparadas sob atmosfera ambiente apresentaram predominantemente as fases hematita e magnetita e nas amostras preparadas sob atmosfera de argônio foi encontrada apenas a magnetita. A área superficial específica e o volume total de poros do carvão ativado foram reduzidos em torno de 40 e 50%, respectivamente, com a formação das nanopartículas. A execução de tratamentos térmicos em atmosfera inerte levou ao crescimento do tamanho médio de cristalito; para temperaturas a partir de 400 oC, aproximadamente, teve início o processo de redução do estado de oxidação do ferro, até temperaturas em torno de 700 oC. Nas amostras tratadas em 900 oC foi observada a predominância de ferro metálico, além da formação de carbetos de ferro. Na análise de difração de raios-X in situ durante o aquecimento das amostras, foi observada a formação da wustita como um composto intermediário antes da formação do ferro metálico. Os valores dos coeficientes de expansão térmica para os óxidos de ferro nanocristalinos foram consideravelmente maiores do que os esperados para as fases cristalinas massivas, um efeito associado à elevada fração de átomos de superfície nas nanopartículas. Os resultados deste trabalho mostraram que os métodos empregados de síntese e posterior tratamento térmico possibilitam a obtenção de nanopartículas magnéticas contendo ferro dispersas na matriz do carvão ativado; a natureza e o tamanho médio dessas partículas dependem das condições experimentais envolvidas, tais como atmosfera de síntese, temperatura e tempo de tratamento térmico

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42\ub74% vs 44\ub72%; absolute difference \u20131\ub769 [\u20139\ub758 to 6\ub711] p=0\ub767; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5\u20138] vs 6 [5\u20138] cm H2O; p=0\ub70011). ICU mortality was higher in MICs than in HICs (30\ub75% vs 19\ub79%; p=0\ub70004; adjusted effect 16\ub741% [95% CI 9\ub752\u201323\ub752]; p<0\ub70001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0\ub780 [95% CI 0\ub775\u20130\ub786]; p<0\ub70001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status. Funding: No funding

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference -1·69 [-9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H2O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52-23·52]; p<0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75-0·86]; p<0·0001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status