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The potential of sawmill wastes as a raw material in pyrolysis process is presented in this study. Non-isothermal thermogravimetric analysis (TGA and DTG) and isoconversional methods were employed to determine triplet kinetic (activation energy, reaction model and pre-exponential factor). Through TGA and DTG, the conversion degree is described as a function of temperature for five heating rates (10, 20, 30, 40 and 50 o C/min) and four model-free methods (Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Friedman, and Vyazovkin) with temperatures ranging from 25 to 1000 ° C were employed. Isoconversional lines were built for every method at different isoconversional degrees α ∈ [ 0,1 ] . The activation energy E was found as a function of α in the interval χ I I = [ 0.2 , 0.7 ] where each isoconversional methods were in agreement and the estimated error was sufficiently small. Findings show the same activation energy profile independently of the isoconversional method. In particular the total variation of E in χ I I was as follows: 209.909-228.238 kJ/mol (FWO); 211.235-229.277 kJ/mol (KAS); 223.050-188.512 kJ/mol (Friedman), and 211.449 kJ/mol-229.512 kJ/mol (Vyazovkin). The reaction model of the process in χ I I matched with a two-dimensional diffusion ( D 2 ) by using a master-plot analysis. The calculated and reported parameters are fundamental information for the pyrolysis reactor design using Sawmill wastes as feedstock.
RESUMO
Introducción: Las infecciones asociadas a ventilación mecánica son causa importante de morbimortalidad en el paciente crítico. La diferenciación entre traqueobronquitis y neumonía no es siempre fácil, y es controvertida. Algunos trabajos describen aumento de mortalidad, mayor estancia en Unidades de Cuidado Intensivo (UCI), mayor requerimiento de ventilación mecánica e incremento de costos en pacientes con traqueobronquitis asociada a ventilador (TAV), sin diferencias significativas en pacientes con neumonía asociada a ventilador (NAV). Estos estudios no describen el comportamiento clínico y epidemiológico de la TAV y la NAV como 2 entidades independientes, por lo que es necesario describirlo. Métodos: Estudio multicéntrico de cohorte prospectiva, de pacientes adultos que desarrollaron TAV o NAV durante su estancia en UCI, entre noviembre de 2013 y octubre de 2014. A cada una de las variables demográficas, clínicas, de laboratorio y de desenlace, como tiempo de ventilación mecánica, estancia hospitalaria y muerte, se le realizó análisis descriptivo; para evaluar las diferencias entre los grupos se utilizó test de chi cuadrado, t de Student o U de Mann Whitney. Resultados: Se incluyó a 143 pacientes, con edad promedio de 55 años, 57% eran hombres, de 6 países en Latinoamérica; 63% con NAV y 37% con TAV. Las comorbilidades más frecuentes fueron cardiovascular (44%) y neurológica (30%); esta última fue más frecuente en TAV (41,5 vs. 23%; p = 0,02). No se encontró diferencia en APACHE II de ingreso. El índice SOFA fue mayor en NAV (8 vs. 5; p = 0,02). No hubo diferencias en el aislamiento microbiológico, ni en los patrones de resistencia bacteriana entre las 2 entidades. Se observó mayor número de complicaciones cardiovasculares y SDRA en pacientes con NAV. No se encontró diferencia entre los 2 grupos en estancia en UCI, los días de ventilación mecánica ni en mortalidad. Conclusiones: La prevalencia de TAV fue mayor a lo descrito hasta ahora en la literatura. No se encontraron diferencias significativas en el aislamiento microbiológico, la resistencia bacteriana ni el esquema antibiótico utilizado en los 2 grupos. Aunque la NAV cursó con mayor proporción de complicaciones médicas asociadas, el hallazgo de una estancia hospitalaria, tiempo de ventilación mecánica y mortalidad similares sustenta la importancia clínica de la TAV.
Introduction: The infections associated with mechanical ventilation are a major cause of morbidity and mortality in critically ill patients. Limited studies report increased mortality and intensive care units (ICU) stays, requirements for mechanical ventilation and higher costs in ventilator-associated tracheobronchitis (TAV) in comparison to patients with ventilator-associated pneumonia (NAV). These studies do not describe the clinical and epidemiological behavior in the same population as independent entities, so it is necessary to describe the epidemiology of patients with TAV and NAV. Methods: Multicenter cross-sectional study of adult patients who developed TAV and/or NAV during their stay in the ICU in 2013 to 2014. A descriptive analysis was performed on each of the variables. For qualitative variables we assessed differences between groups using the Chi-squared test; for continuous variables, we used Student's t test or the Mann Whitney U test. Results: A total of 147 patients from 6 countries in Latin America were included; 63% with NAV and 37% with TAV. The average age was 55 years; 57% male. The most frequent comorbidity was cardiovascular (44%) and neurological (30%), the latter was more frequent in those with TAV (41.5 vs. 23%, P = .02). No differences were found in APACHE II on entry, but the difference appears in the SOFA index (8 vs. 5, P = .02). There were no differences in microbiological isolation, or bacterial resistance patterns between the 2 entities. A greater number of cardiovascular complications and ARDS were observed in patients with NAV. The ICU stay, days on mechanical ventilation and mortality were not different between the 2 groups. Conclusions: The TAV prevalence was higher than heretofore described in the literature. No significant differences were found in the microbiological isolation, bacterial resistance and antibiotic therapy used in the 2 groups, which might suggest that therapeutic approach be similar to that recommended for NAV. No differences were observed in clinical outcomes such as hospital stay, duration of mechanical ventilation and mortality, although NAV was associated with a greater proportion of medical complications.
