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BACKGROUND: We hypothesized that a decrease in frequency of controlled breaths during biphasic positive airway pressure (BIVENT), associated with an increase in spontaneous breaths, whether pressure support (PSV)-assisted or not, would mitigate lung and diaphragm damage in mild experimental acute respiratory distress syndrome (ARDS). MATERIALS AND METHODS: Wistar rats received Escherichia coli lipopolysaccharide intratracheally. After 24 hours, animals were randomly assigned to: 1) BIVENT-100+PSV0%: airway pressure (Phigh) adjusted to VT = 6 mL/kg and frequency of controlled breaths (f) = 100 bpm; 2) BIVENT-50+PSV0%: Phigh adjusted to VT = 6 mL/kg and f = 50 bpm; 3) BIVENT-50+PSV50% (PSV set to half the Phigh reference value, i.e., PSV50%); or 4) BIVENT-50+PSV100% (PSV equal to Phigh reference value, i.e., PSV100%). Positive end-expiratory pressure (Plow) was equal to 5 cmH2O. Nonventilated animals were used for lung and diaphragm histology and molecular biology analysis. RESULTS: BIVENT-50+PSV0%, compared to BIVENT-100+PSV0%, reduced the diffuse alveolar damage (DAD) score, the expression of amphiregulin (marker of alveolar stretch) and muscle atrophy F-box (marker of diaphragm atrophy). In BIVENT-50 groups, the increase in PSV (BIVENT-50+PSV50% versus BIVENT-50+PSV100%) yielded better lung mechanics and less alveolar collapse, interstitial edema, cumulative DAD score, as well as gene expressions associated with lung inflammation, epithelial and endothelial cell damage in lung tissue, and muscle ring finger protein 1 (marker of muscle proteolysis) in diaphragm. Transpulmonary peak pressure (Ppeak,L) and pressure-time product per minute (PTPmin) at Phigh were associated with lung damage, while increased spontaneous breathing at Plow did not promote lung injury. CONCLUSION: In the ARDS model used herein, during BIVENT, the level of PSV and the phase of the respiratory cycle in which the inspiratory effort occurs affected lung and diaphragm damage. Partitioning of inspiratory effort and transpulmonary pressure in spontaneous breaths at Plow and Phigh is required to minimize VILI.

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BACKGROUND: Obesity is associated with a chronic systemic inflammatory process. Volatile or intravenous anesthetic agents may modulate immune function, and may do so differentially in obesity. However, no study has evaluated whether these potential immunomodulatory effects differ according to type of anesthesia in obese patients undergoing laparoscopic bariatric surgery. METHODS/DESIGN: The OBESITA trial is a prospective, nonblinded, single-center, randomized, controlled clinical pilot trial. The trial will include 48 patients with a body mass index ≥ 35 kg/m2, scheduled for laparoscopic bariatric surgery using sleeve or a Roux-en-Y gastric bypass technique, who will be allocated 1:1 to undergo general inhalational anesthesia with sevoflurane or total intravenous anesthesia (TIVA) with propofol. The primary endpoint is the difference in plasma interleukin (IL)-6 levels when comparing the two anesthetic agents. Blood samples will be collected prior to anesthesia induction (baseline), immediately after anesthetic induction, and before endotracheal extubation. Levels of other proinflammatory and anti-inflammatory cytokines, neutrophil chemotaxis, macrophage differentiation, phagocytosis, and occurrence of intraoperative and postoperative complications will also be evaluated. DISCUSSION: To our knowledge, this is the first randomized clinical trial designed to compare the effects of two different anesthetics on immunomodulation in obese patients undergoing laparoscopic bariatric surgery. Our hypothesis is that anesthesia with sevoflurane will result in a weaker proinflammatory response compared to anesthesia with propofol, with lower circulating levels of IL-6 and other proinflammatory mediators, and increased macrophage differentiation into the M2 phenotype in adipose tissue. TRIAL REGISTRATION: Registro Brasileiro de Ensaios Clínicos, RBR-77kfj5 . Registered on 25 July 2018.

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OBJECTIVE: Glycemic control has been increasingly recognized as a critical element in inpatient care, but optimal management of blood glucose in the hospital setting remains challenging. The aims of this study were to describe and evaluate the impact of the implementation of an inpatient multidisciplinary glucose control management program on glucose control in hospitalized patients. MATERIALS AND METHODS: Retrospective analysis of medical records and glucose monitoring data obtained by point- of-care testing (POCT) in hospitalized patients before (May 2014) and after (June 2015 and May 2017) the implementation of the program. RESULTS: We analyzed 6888, 7290, and 7669 POCTs from 389, 545, and 475 patients in May 2014, June 2015, and May 2017, respectively. Hyperglycemia (≥ 180 mg/ dL) occurred in 23.5%, 19.6%, and 19.3% POCTs in May 2014, June 2015, and May/2017, respectively (p < 0.001), while severe hyperglycemia (≥ 300 mg/dL) was observed in 2.5%, 2.2%, and 1.8% of them, respectively (p = 0.003). Hyperglycemia (≥ 180 mg/dL) reduced significantly from May 2014 to June 2015 (16.3%, p < 0.001) and from May 2014 to May 2017 (178%, p < 0.001). No significant changes occurred in hypoglycemic parameters. CONCLUSIONS: The implementation of an inpatient multidisciplinary glucose control management program led to significant reductions in hyperglycemic events. The key elements for this achievement were the development of institutional inpatient glycemic control protocols, establishment of a multidisciplinary team, and continuing educational programs for hospital personnel. Altogether, these actions resulted in improvements in care processes, patient safety, and clinical outcomes of hospitalized patients.

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ABSTRACT Objective: Glycemic control has been increasingly recognized as a critical element in inpatient care, but optimal management of blood glucose in the hospital setting remains challenging. The aims of this study were to describe and evaluate the impact of the implementation of an inpatient multidisciplinary glucose control management program on glucose control in hospitalized patients. Materials and methods: Retrospective analysis of medical records and glucose monitoring data obtained by point- of-care testing (POCT) in hospitalized patients before (May 2014) and after (June 2015 and May 2017) the implementation of the program. Results: We analyzed 6888, 7290, and 7669 POCTs from 389, 545, and 475 patients in May 2014, June 2015, and May 2017, respectively. Hyperglycemia (≥ 180 mg/ dL) occurred in 23.5%, 19.6%, and 19.3% POCTs in May 2014, June 2015, and May/2017, respectively (p < 0.001), while severe hyperglycemia (≥ 300 mg/dL) was observed in 2.5%, 2.2%, and 1.8% of them, respectively (p = 0.003). Hyperglycemia (≥ 180 mg/dL) reduced significantly from May 2014 to June 2015 (16.3%, p < 0.001) and from May 2014 to May 2017 (178%, p < 0.001). No significant changes occurred in hypoglycemic parameters. Conclusions: The implementation of an inpatient multidisciplinary glucose control management program led to significant reductions in hyperglycemic events. The key elements for this achievement were the development of institutional inpatient glycemic control protocols, establishment of a multidisciplinary team, and continuing educational programs for hospital personnel. Altogether, these actions resulted in improvements in care processes, patient safety, and clinical outcomes of hospitalized patients.

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A síndrome do desconforto respiratório agudo (SDRA) resulta em grande área de colapso pulmonar, e apresenta-se morfologicamente como um pulmão de bebê ou baby lung. Apesar da utilização de estratégias ventilatórias consideradas protetoras, essas não são suficientes para proporcionar proteção em alguns pacientes mais graves, que têm indicação de se implementar outras técnicas alternativas ou de resgate para que se preserve a estrutura morfofuncional pulmonar. As técnicas de assistência pulmonar extracorpórea (APE) sustentam a troca gasosa adequada, seja através de oxigenação e controle da hipercapnia (oxigenação por membrana extracorpórea - ECMO), ou apenas pelo controle da hipercapnia (remoção de dióxido de carbono extracórporeo em circuito modificado de hemodiálise - ECCO2 R, ou através da assistência pulmonar intervencionista – iLA), o que auxilia no ajuste ventilatório para promoção da proteção pulmonar adequada. Entretanto, são técnicas invasivas que podem impor considerável risco ao paciente, e por isso, deverão ser usadas em centros com experiência em sua utilização. Nessa revisão, serão discutidos os princípios fisiológicos da troca e transporte de gases, assim como as principais técnicas de APE: ECMO, ECCO2R e iLA, onde serão descritas suas indicações, características funcionais, contraindicações e resultados experimentais e clínicos mais relevantes...

The acute respiratory distress syndrome (ARDS) results in considerable area of pulmonary colapse and may be morphologically considered as a baby lung. Despite of the use of protective ventilatory strategies, in some very critically ill patients those strategies are not enough to protect the lungs. At this point alternative or rescue therapies are indicated to preserve the morphofunctional structure of the lungs.The extracorporeal pulmonary assistance (APE) techniques support adequate gas exchange by oxigenation and hypercapnia control (extracorporeal membrane oxygenation – ECMO), or just by hypercapnia control (extracorporeal carbon dioxide removal using a modified hemodyalisis circuit - ECCO2R, or by interventional lung assist - iLA) which allow to set ventilatory parameters to adequately protect the lungs. However these techniques are invasive and may impose considerable risks to the patient and that is why it must be used in refferal hospital centers. In this review will be discussed physiological principles of gas exchange and transport, as well as the main EPA techniques: ECMO, ECCO2R and iLA. Indications, functional characteristics, contraindications and relevant experimental and clinical results...

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Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

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O suporte ventilatório artificial invasivo e não invasivo ao paciente grave tem evoluído e inúmeras evidências têm surgido, podendo ter impacto na melhora da sobrevida e da qualidade do atendimento oferecido nas unidades de terapia intensiva no Brasil. Isto posto, a Associação de Medicina Intensiva Brasileira (AMIB) e a Sociedade Brasileira de Pneumologia e Tisiologia (SBPT) - representadas por seu Comitê de Ventilação Mecânica e sua Comissão de Terapia Intensiva, respectivamente, decidiram revisar a literatura e preparar recomendações sobre ventilação mecânica, objetivando oferecer aos associados um documento orientador das melhores práticas da ventilação mecânica na beira do leito, com base nas evidências existentes, sobre os 29 subtemas selecionados como mais relevantes no assunto. O projeto envolveu etapas que visaram distribuir os subtemas relevantes ao assunto entre experts indicados por ambas as sociedades, que tivessem publicações recentes no assunto e/ou atividades relevantes em ensino e pesquisa no Brasil, na área de ventilação mecânica. Esses profissionais, divididos por subtemas em duplas, responsabilizaram-se por fazer uma extensa revisão da literatura mundial. Reuniram-se todos no Fórum de Ventilação Mecânica, na sede da AMIB, na cidade de São Paulo (SP), em 3 e 4 de agosto de 2013, para finalização conjunta do texto de cada subtema e apresentação, apreciação, discussão e aprovação em plenária pelos 58 participantes, permitindo a elaboração de um documento final.

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

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Assisted mechanical ventilation (MV) may be a favorable alternative to controlled MV at the early phase of acute respiratory distress syndrome (ARDS), since it requires less sedation, no paralysis and is associated with less hemodynamic deterioration, better distal organ perfusion, and lung protection, thus reducing the risk of ventilator-associated lung injury (VALI). In the present review, we discuss VALI in relation to assisted MV strategies, such as volume assist-control ventilation, pressure assist-control ventilation, pressure support ventilation (PSV), airway pressure release ventilation (APRV), APRV with PSV, proportional assist ventilation (PAV), noisy ventilation, and neurally adjusted ventilatory assistance (NAVA). In summary, we suggest that assisted MV can be used in ARDS patients in the following situations: (1) Pao(2)/Fio(2) >150 mm Hg and positive end-expiratory pressure ≥ 5 cm H(2)O and (2) with modalities of pressure-targeted and time-cycled breaths including more or less spontaneous or supported breaths (A-PCV [assisted pressure-controlled ventilation] or APRV). Furthermore, during assisted MV, the following parameters should be monitored: inspiratory drive, transpulmonary pressure, and tidal volume (6 mL/kg). Further studies are required to determine the impact of novel modalities of assisted ventilation such as PAV, noisy pressure support, and NAVA on VALI.

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Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumonia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

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O suporte ventilatório artificial invasivo e não invasivo ao paciente crítico tem evoluído e inúmeras evidências têm surgido, podendo ter impacto na melhora da sobrevida e da qualidade do atendimento oferecido nas unidades de terapia intensiva no Brasil. Isto posto, a Associação de Medicina Intensiva Brasileira (AMIB) e a Sociedade Brasileira de Pneumonia e Tisiologia (SBPT) - representadas pelo seus Comitê de Ventilação Mecânica e Comissão de Terapia Intensiva, respectivamente, decidiram revisar a literatura e preparar recomendações sobre ventilação mecânica objetivando oferecer aos associados um documento orientador das melhores práticas da ventilação mecânica na beira do leito, baseado nas evidencias existentes, sobre os 29 subtemas selecionados como mais relevantes no assunto. O projeto envolveu etapas visando distribuir os subtemas relevantes ao assunto entre experts indicados por ambas as sociedades que tivessem publicações recentes no assunto e/ou atividades relevantes em ensino e pesquisa no Brasil na área de ventilação mecânica. Esses profissionais, divididos por subtemas em duplas, responsabilizaram-se por fazer revisão extensa da literatura mundial sobre cada subtema. Reuniram-se todos no Forum de Ventilação Mecânica na sede da AMIB em São Paulo, em 03 e 04 de agosto de 2013 para finalização conjunta do texto de cada subtema e apresentação, apreciação, discussão e aprovação em plenária pelos 58 participantes, permitindo a elaboração de um documento final.

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associação de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumonia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in São Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

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INTRODUCTION: Biphasic positive airway pressure (BIVENT) is a partial support mode that employs pressure-controlled, time-cycled ventilation set at two levels of continuous positive airway pressure with unrestricted spontaneous breathing. BIVENT can modulate inspiratory effort by modifying the frequency of controlled breaths. Nevertheless, the optimal amount of inspiratory effort to improve respiratory function while minimizing ventilator-associated lung injury during partial ventilatory assistance has not been determined. Furthermore, it is unclear whether the effects of partial ventilatory support depend on acute lung injury (ALI) etiology. This study aimed to investigate the impact of spontaneous and time-cycled control breaths during BIVENT on the lung and diaphragm in experimental pulmonary (p) and extrapulmonary (exp) ALI. METHODS: This was a prospective, randomized, controlled experimental study of 60 adult male Wistar rats. Mild ALI was induced by Escherichia coli lipopolysaccharide either intratracheally (ALI(p)) or intraperitoneally (ALI(exp)). After 24 hours, animals were anesthetized and further randomized as follows: (1) pressure-controlled ventilation (PCV) with tidal volume (V(t)) = 6 ml/kg, respiratory rate = 100 breaths/min, PEEP = 5 cmH2O, and inspiratory-to-expiratory ratio (I:E) = 1:2; or (2) BIVENT with three spontaneous and time-cycled control breath modes (100, 75, and 50 breaths/min). BIVENT was set with two levels of CPAP (P(high) = 10 cmH2O and P(low) = 5 cmH2O). Inspiratory time was kept constant (T(high) = 0.3 s). RESULTS: BIVENT was associated with reduced markers of inflammation, apoptosis, fibrogenesis, and epithelial and endothelial cell damage in lung tissue in both ALI models when compared to PCV. The inspiratory effort during spontaneous breaths increased during BIVENT-50 in both ALI models. In ALI(p), alveolar collapse was higher in BIVENT-100 than PCV, but decreased during BIVENT-50, and diaphragmatic injury was lower during BIVENT-50 compared to PCV and BIVENT-100. In ALI(exp), alveolar collapse during BIVENT-100 and BIVENT-75 was comparable to PCV, while decreasing with BIVENT-50, and diaphragmatic injury increased during BIVENT-50. CONCLUSIONS: In mild ALI, BIVENT had a lower biological impact on lung tissue compared to PCV. In contrast, the response of atelectasis and diaphragmatic injury to BIVENT differed according to the rate of spontaneous/controlled breaths and ALI etiology.

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Introdução: O choque séptico é a principal causa de morte nas unidades de terapia intensiva, sendo a depressão miocárdica um importante fator causal nesse desfecho. Objetivo: Avaliar a função ventricular e o tipo de alteração contrátil (regional ou difusa) presentes em pacientes na fase aguda da sepsis e sua correlação com marcadores de injúrias miocárdica e mortalidade. Método: Foram estudados prospectiva e, consecutivamente, 45 pacientes sépticos, admitidos na unidade de terapia intensiva no período de 24 meses. Foi realizado um ecocardiograma transtorácico (ETT) na fase aguda da sepsis, junto com ecocardiograma (ECG) e dosagem sérica troponina I (TNI). Em um segundo momento, foram analisadas a frequência e a correlação das alterações funcionais ao ecocardiograma, da elevação da TNI e a taxa de mortalidade dos pacientes. O ETT foi repetido nos pacientes que sobreviveram após a resolução do quadro séptico. Resultados: Dos 45 pacientes estudados, o ECG mostrou alterações isquêmicas em 40% e o ecocardiograma apresentou alteração regional ou difusa em 44% dos pacientes estudados. A TNI esteve elevada em 53% dos pacientes, dos quais 77% apresentavam disfunção ventricular esquerda (DVE) na fase aguda da sepsis. O ETT evolutivo foi realizado em 24 pacientes (53%%), mostrando melhora parcial...

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BACKGROUND: Delirium features can vary greatly depending on the postoperative population studied; however, most studies focus only on high-risk patients. Describing the impact of delirium and risk factors in mixed populations can help in the development of preventive actions. METHODS: The occurrence of delirium was evaluated prospectively in 465 consecutive nonventilated postoperative patients admitted to a surgical intensive care unit (SICU) using the confusion assessment method (CAM). Patients with and without delirium were compared. A multiple logistic regression was performed to identify the main risk factors for delirium in the first 24 h of admission to the SICU and the main predictors of outcomes. RESULTS: Delirium was diagnosed in 43 (9.2%) individuals and was more frequent on the second and third days of admission. The presence of delirium resulted in longer lengths of SICU and hospital stays [6 days (3-13) vs. 2 days (1-3), p < 0.001 and 26 days (12-39) vs. 6 days (3-13), p <0.001, respectively], as well as higher hospital and SICU mortality rates [16.3% vs. 4.0%, p = 0.004 and 6.5% vs. 1.7%, p = 0.042, respectively]. The risk factors for delirium were age (odds ratio (OR), 1.04 [1.02-1.07]), Acute Physiologic Score (APS; OR, 1.11 [1.04-1.2]), emergency surgery (OR, 8.05 [3.58-18.06]), the use of benzodiazepines (OR, 2.28 [1.04-5.00]), and trauma (OR, 6.16 [4.1-6.5]). CONCLUSIONS: Delirium negatively impacts postoperative nonventilated patients. Risk factors can be used to detect high-risk patients in a mixed population of SICU patients.

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OBJECTIVE: To investigate the effects of the rate of airway pressure increase and duration of recruitment maneuvers on lung function and activation of inflammation, fibrogenesis, and apoptosis in experimental acute lung injury. DESIGN: Prospective, randomized, controlled experimental study. SETTING: University research laboratory. SUBJECTS: Thirty-five Wistar rats submitted to acute lung injury induced by cecal ligation and puncture. INTERVENTIONS: After 48 hrs, animals were randomly distributed into five groups (seven animals each): 1) nonrecruited (NR); 2) recruitment maneuvers (RMs) with continuous positive airway pressure (CPAP) for 15 secs (CPAP15); 3) RMs with CPAP for 30 secs (CPAP30); 4) RMs with stepwise increase in airway pressure (STEP) to targeted maximum within 15 secs (STEP15); and 5) RMs with STEP within 30 secs (STEP30). To perform STEP RMs, the ventilator was switched to a CPAP mode and positive end-expiratory pressure level was increased stepwise. At each step, airway pressure was held constant. RMs were targeted to 30 cm H2O. Animals were then ventilated for 1 hr with tidal volume of 6 mL/kg and positive end-expiratory pressure of 5 cm H2O. MEASUREMENTS AND MAIN RESULTS: Blood gases, lung mechanics, histology (light and electronic microscopy), interleukin-6, caspase 3, and type 3 procollagen mRNA expressions in lung tissue. All RMs improved oxygenation and lung static elastance and reduced alveolar collapse compared to NR. STEP30 resulted in optimal performance, with: 1) improved lung static elastance vs. NR, CPAP15, and STEP15; 2) reduced alveolar-capillary membrane detachment and type 2 epithelial and endothelial cell injury scores vs. CPAP15 (p < .05); and 3) reduced gene expression of interleukin-6, type 3 procollagen, and caspase 3 in lung tissue vs. other RMs. CONCLUSIONS: Longer-duration RMs with slower airway pressure increase efficiently improved lung function, while minimizing the biological impact on lungs.

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A mecânica do sistema respiratório é um alicerce fundamental para o entendimento da ventilação mecânica, seus efeitos e aplicações clínicas. A presente revisão discute as bases para a mensuração e análise da mecânica respiratória na síndrome de desconforto respiratório agudo (SDRA), assim como suas implicações no diagnóstico e estratégias ventilatórias. Ademais, ressalta as evidências mais significativas da literatura acerca da importância do estudo da mecânica respiratória para a proteção pulmonar e melhora do prognóstico de pacientes com SDRA.

The analysis of respiratory system mechanics is essential for the understanding of mechanical ventilation, its effect and clinical applications. The present revision presents the basis for the measurement and analysis of respiratory mechanics in acute respiratory distress syndrome (ARDS), as well as its implications in the diagnosis and ventilator strategies. Additionally, this revision focused on the most important evidence of the literature concerning the importance of respiratory mechanics analysis for lung protection and ARDS patients’ prognosis.

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A estratégia ventilatória adotada na lesão pulmonar aguda/síndrome do desconforto respiratório agudo (LPA/SDRA) é conhecida como estratégia protetora e consiste em redução do volume corrente, limitação de pressões pulmonares e ajuste adequado da pressão expiratória final positiva, usualmente em modalidade ventilatória controlada. Entretanto, trabalhos experimentais e clínicos têm demonstrado os benefícios da ventilação assistida para pacientes com LPA. A ativação dos músculos respiratórios, associada à ventilação assistida, reduz a pressão pleural e ajusta a relação ventilação--perfusão, que está relacionada ao aumento da pressão transpulmonar, protege órgãos à distância, reduz o comprometimento hemodinâmico e a atrofia dos músculos respiratórios. A presente revisão descreve os princípios e as evidências científicas mais recentes quanto à utilização de modos ventilatórios assistidos durante a fase inicial da LPA/SDRA.

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A síndrome do desconforto respiratório agudo resulta em grande área de colapso pulmonar e apresenta-se morfologicamente como um pulmão de bebê ou baby lung. Apesar da utilização de estratégias ventilatórias consideradas protetoras,essas não são suficientes para proporcionar proteção em alguns pacientes mais graves, que têm indicação de uso de outras técnicas alternativas ou de resgate para que se preserve a estrutura morfofuncional pulmonar. As técnicas de assistência pulmonar extracorpórea sustentam a troca gasosa adequada, seja através de oxigenação e controle da hipercapnia (oxigenação por membrana extracorpórea), ou apenas pelo controle da hipercapnia (remoção extracorpórea de dióxido de carbono em circuito modificado de hemodiálise ou através de assistência pulmonar intervencionista), o que auxilia no ajuste ventilatório para a promoção da proteção pulmonar adequada. Entretanto, são técnicas invasivas que podem impor considerável risco ao paciente e, por isso, deverão ser usadas em centros com experiência em sua utilização. Nesta revisão, serão discutidos os princípios fisiológicos da troca e transporte de gases, assim como as principais técnicas de assistência pulmonar extracorpórea, com suas indicações, características funcionais, contraindicações e resultados experimentais e clínicos mais relevantes.

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PURPOSE: The goal of the study was to compare the effects of different assisted ventilation modes with pressure controlled ventilation (PCV) on lung histology, arterial blood gases, inflammatory and fibrogenic mediators in experimental acute lung injury (ALI). METHODS: Paraquat-induced ALI rats were studied. At 24 h, animals were anaesthetised and further randomized as follows (n = 6/group): (1) pressure controlled ventilation mode (PCV) with tidal volume (V (T)) = 6 ml/kg and inspiratory to expiratory ratio (I:E) = 1:2; (2) three assisted ventilation modes: (a) assist-pressure controlled ventilation (APCV1:2) with I:E = 1:2, (b) APCV1:1 with I:E = 1:1; and (c) biphasic positive airway pressure and pressure support ventilation (BiVent + PSV), and (3) spontaneous breathing without PEEP in air. PCV, APCV1:1, and APCV1:2 were set with P (insp) = 10 cmH(2)O and PEEP = 5 cmH(2)O. BiVent + PSV was set with two levels of CPAP [inspiratory pressure (P (High) = 10 cmH(2)O) and positive end-expiratory pressure (P (Low) = 5 cmH(2)O)] and inspiratory/expiratory times: T (High) = 0.3 s and T (Low) = 0.3 s. PSV was set as follows: 2 cmH(2)O above P (High) and 7 cmH(2)O above P (Low). All rats were mechanically ventilated in air and PEEP = 5 cmH(2)O for 1 h. RESULTS: Assisted ventilation modes led to better functional improvement and less lung injury compared to PCV. APCV1:1 and BiVent + PSV presented similar oxygenation levels, which were higher than in APCV1:2. Bivent + PSV led to less alveolar epithelium injury and lower expression of tumour necrosis factor-alpha, interleukin-6, and type III procollagen. CONCLUSIONS: In this experimental ALI model, assisted ventilation modes presented greater beneficial effects on respiratory function and a reduction in lung injury compared to PCV. Among assisted ventilation modes, Bi-Vent + PSV demonstrated better functional results with less lung damage and expression of inflammatory mediators.

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