Influencia de la caja torácica en el monitoreo de la mecánica respiratoria en síndrome de distrés respiratorio agudo / Chest wall effect on the monitoring of respiratory mechanics in acute respiratory distress syndrome

RESUMEN La mecánica del sistema respiratorio depende de las características del pulmón, la caja torácica y su interacción. En pacientes con síndrome de distrés respiratorio agudo bajo ventilación mecánica el monitoreo de la presión meseta en la vía aérea es fundamental debido a su valor pronóstico y su capacidad de reflejar el estrés pulmonar. Sin embargo, su validez puede verse afectada por cambios en las características mecánicas de la caja torácica, y además, no otorga información para la correcta titulación de presión positiva al final de la espiración en función de restablecer el volumen pulmonar. La influencia que la caja torácica ejerce sobre la mecánica del sistema respiratorio en síndrome de distrés respiratorio agudo no ha sido completamente descripta y es probable que haya sido sobredimensionada pudiendo conducir a toma de decisiones erróneas. Ante la insuflación con presión positiva al final de la espiración, la carga impuesta por la caja torácica es despreciable. En condiciones dinámicas, desplazar esta estructura demanda un cambio de presión cuya magnitud se relaciona con sus características mecánicas, dicha carga se mantiene constante independientemente del volumen a partir del cual es insuflada. Por lo que cambios en la presión en la vía aérea reflejan modificaciones en las condiciones mecánicas del pulmón. El monitoreo avanzado podría reservarse para pacientes con incremento de la presión intra-abdominal en los que no pueda implementarse una estrategia de ventilación mecánica protectora. Las estimaciones de reclutamiento alveolar basadas en la mecánica del sistema respiratorio podrían ser reflejo del diferente comportamiento de la caja torácica a la insuflación y no verdadero reclutamiento alveolar.

ABSTRACT The respiratory system mechanics depend on the characteristics of the lung and chest wall and their interaction. In patients with acute respiratory distress syndrome under mechanical ventilation, the monitoring of airway plateau pressure is fundamental given its prognostic value and its capacity to assess pulmonary stress. However, its validity can be affected by changes in mechanical characteristics of the chest wall, and it provides no data to correctly titrate positive end-expiratory pressure by restoring lung volume. The chest wall effect on respiratory mechanics in acute respiratory distress syndrome has not been completely described, and it has likely been overestimated, which may lead to erroneous decision making. The load imposed by the chest wall is negligible when the respiratory system is insufflated with positive end-expiratory pressure. Under dynamic conditions, moving this structure demands a pressure change whose magnitude is related to its mechanical characteristics, and this load remains constant regardless of the volume from which it is insufflated. Thus, changes in airway pressure reflect changes in the lung mechanical conditions. Advanced monitoring could be reserved for patients with increased intra-abdominal pressure in whom a protective mechanical ventilation strategy cannot be implemented. The estimates of alveolar recruitment based on respiratory system mechanics could reflect differences in chest wall response to insufflation and not actual alveolar recruitment.

O que todo intensivista deve saber a respeito da síndrome do desconforto respiratório agudo e dano alveolar difuso? / What every intensivist should know about acute respiratory distress syndrome and diffuse alveolar damage

RESUMO A síndrome do desconforto respiratório agudo é um desafio para o intensivista. A característica principal desta doença aguda é o dano alveolar difuso, presente em cerca de metade dos pacientes com a síndrome. É claro que o suporte respiratório à síndrome do desconforto respiratório agudo tem melhorado gradualmente nas últimas décadas. É também evidente que todos estes procedimentos são benéficos, já que reduzem a lesão pulmonar e mantêm o paciente vivo. Isto deve ser interpretado como uma estratégia de ganho de tempo, até que o fator desencadeante ou de risco causal melhore, assim como a tempestade inflamatória diminua e o pulmão se cure. Por outro lado, todos - exceto dois tratamentos farmacológicos (bloqueadores neuromusculares e esteroides) - são incapazes de melhorar o desfecho da síndrome do desconforto respiratório agudo. A hipótese de que os resultados farmacológicos negativos podem ser explicados pela heterogeneidade histológica da síndrome do desconforto respiratório agudo tem sido apoiada pelas recentes demonstrações de que a síndrome com dano alveolar difuso tem característica clínico-patológica específica. O dano alveolar difuso é um diagnóstico patológico, e a biópsia pulmonar a céu aberto (a técnica mais comum para obtenção de tecido pulmonar) tem efeitos colaterais graves, sendo necessário que se desenvolvam biomarcadores substitutos para o dano alveolar difuso. O objetivo desta revisão é discutir três tópicos relacionados à síndrome do desconforto respiratório agudo: o relacionamento entre a síndrome do desconforto respiratório agudo e o dano alveolar difuso; como o dano alveolar difuso pode ser representado no quadro clínico; e como o enriquecimento pode melhorar os resultados de estudos clínicos farmacológicos realizados com pacientes com a síndrome e com dano alveolar difuso.

ABSTRACT Acute respiratory distress syndrome is a challenging entity for the intensivist. The pathological hallmark of the acute phase is diffuse alveolar damage, which is present in approximately half of living patients with acute respiratory distress syndrome. It is clear that respiratory support for acute respiratory distress syndrome has gradually been improving over recent decades. However, it is also evident that these procedures are beneficial, as they reduce lung injury and keep the patient alive. This could be interpreted as a time-gaining strategy until the trigger or causal or risk factor improves, the inflammatory storm decreases and the lung heals. However, all except two pharmacological treatments (neuromuscular blockers and steroids) were unable to improve the acute respiratory distress syndrome outcome. The hypothesis that pharmacological negative results may be explained by the histological heterogeneity of acute respiratory distress syndrome has been supported by the recent demonstration that acute respiratory distress syndrome with diffuse alveolar damage constitutes a specific clinical-pathological entity. Given that diffuse alveolar damage is a pathological diagnosis and that open lung biopsy (the most common technique to obtain lung tissue) has several side effects, it is necessary to develop surrogate biomarkers for diffuse alveolar damage. The aim of this narrative review is to address the following three topics related to acute respiratory distress syndrome: (a) the relationship between acute respiratory distress syndrome and diffuse alveolar damage, (b) how diffuse alveolar damage could be surrogated in the clinical setting and (c) how enrichment in diffuse alveolar damage may improve the results of pharmacological clinical trials tried out on patients with acute respiratory distress syndrome.

Effects of the positive end-expiratory pressure increase on sublingual microcirculation in patients with acute respiratory distress syndrome / Efeitos do aumento de pressão positiva ao final da expiração sobre a microcirculação sublingual em pacientes com síndrome do desconforto respiratório agudo

Abstract Objective: The aim of this study was to evaluate the impact of increased positive end-expiratory pressure on the sublingual microcirculation. Methods: Adult patients who were sedated, under mechanical ventilation, and had a diagnosis of circulatory shock and acute respiratory distress syndrome were included. The positive end-expiratory pressure level was settled to obtain a plateau pressure of 30 cm H2O and then maintained at this level for 20 minutes. Microcirculatory (obtained by videomicroscopy) and hemodynamic variables were collected at baseline and compared with those at the end of 20 min. Results: Twelve patients were enrolled. Overall, the microcirculation parameters did not significantly change after increasing the positive end-expiratory pressure. However, there was considerable interindividual variability. There was a negative, moderate correlation between the changes in the De Backer score (r = -0.58, p = 0.048), total vessel density (r = -0.60, p = 0.039) and baseline values. The changes in total vessel density (r = 0.54, p = 0.07) and perfused vessel density (r = 0.52, p = 0.08) trended toward correlating with the changes in the mean arterial pressure. Conclusion: Overall, the microcirculation parameters did not significantly change after increasing the positive end-expiratory pressure. However, at individual level, such response was heterogeneous. The changes in the microcirculation parameters could be correlated with the baseline values and changes in the mean arterial pressure.

Resumo Objetivo: O objetivo deste estudo foi avaliar o impacto do aumento de pressão positiva no fim da expiração (PEEP) sobre a microcirculação sublingual. Métodos: Os pacientes adultos que foram sedados, sob ventilação mecânica, com diagnóstico de choque circulatório e síndrome do desconforto respiratório agudo foram incluídos. O nível da PEEP foi estabelecido para obter uma pressão de platô de 30 cmH2O e depois mantido nesse nível por 20 minutos. As variáveis de microcirculação (obtida por microscopia de vídeo) e hemodinâmica foram registradas na fase basal e comparadas com aquelas no fim de 20 min. Resultados: Doze pacientes foram incluídos. Em geral, os parâmetros da microcirculação não apresentaram alterações significativas após o aumento da PEEP. Porém, houve considerável variabilidade interindividual. Houve uma correlação negativa, moderada, entre as alterações no escore de De Backer (r = -0,58, p = 0,048), na densidade total do vaso (r = -0,60, p = 0,039) e nos valores basais. As alterações na densidade total do vaso (r = 0,54, p = 0,07) e na densidade do vaso perfundido (r = 0,52, p = 0,08) apresentaram tendência de correlação com as alterações na pressão arterial média. Conclusão: Em geral, os parâmetros da microcirculação não apresentaram alterações significativas após o aumento da PEEP. No entanto, individualmente, essa resposta foi heterogênea. As alterações nos parâmetros da microcirculação puderam ser correlacionadas com os valores basais e alterações na pressão arterial média.

Effect of rhubarb on extravascular lung water in patients with acute respiratory distress syndrome

Summary Objective: The aim of this study was to evaluate the effect of rhubarb on extravascular lung water (EVLW) in patients with acute respiratory distress syndrome (ARDS). Method: A total of 80 patients with ARDS were randomly divided into a treatment group (40 cases) and control group (40 cases). Patients in the treatment group received rhubarb (30.0 g/d) and patients in the control group received conventional therapy for seven consecutive days. Extravascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI) were determined using pulse contour cardiac output (PiCCO) technology, and the oxygenation index was measured by blood gas analysis at baseline and on days 3, 5 and 7 after treatment. Results: The oxygenation index was higher and the levels of EVLWI and PVPI were lower after treatment in the two groups; however, these indexes showed significant differences on the 5th and 7th days after rhubarb treatment compared with the results in the control group (p<0.05). Conclusion: Rhubarb can decrease EVLWI and PVPI, and improve oxygenation in patients with ARDS.

Extracorporeal respiratory support in adult patients / Suporte respiratório extracorpóreo em pacientes adultos

ABSTRACT In patients with severe respiratory failure, either hypoxemic or hypercapnic, life support with mechanical ventilation alone can be insufficient to meet their needs, especially if one tries to avoid ventilator settings that can cause injury to the lungs. In those patients, extracorporeal membrane oxygenation (ECMO), which is also very effective in removing carbon dioxide from the blood, can provide life support, allowing the application of protective lung ventilation. In this review article, we aim to explore some of the most relevant aspects of using ECMO for respiratory support. We discuss the history of respiratory support using ECMO in adults, as well as the clinical evidence; costs; indications; installation of the equipment; ventilator settings; daily care of the patient and the system; common troubleshooting; weaning; and discontinuation.

RESUMO Em pacientes com insuficiência respiratória grave (hipoxêmica ou hipercápnica), o suporte somente com ventilação mecânica pode ser insuficiente para suas necessidades, especialmente quando se tenta evitar o uso de parâmetros ventilatórios que possam causar danos aos pulmões. Nesses pacientes, extracorporeal membrane oxygenation (ECMO, oxigenação extracorpórea por membrana), que também é muito eficaz na remoção de dióxido de carbono do sangue, pode manter a vida, permitindo o uso de ventilação pulmonar protetora. No presente artigo de revisão, objetivamos explorar alguns dos aspectos mais relevantes do suporte respiratório por ECMO. Discutimos a história do suporte respiratório por ECMO em adultos; evidências clínicas; custos; indicações; instalação do equipamento; parâmetros ventilatórios; cuidado diário do paciente e do sistema; solução de problemas comuns; desmame e descontinuação.

Decúbito prono en pacientes con síndrome de distrés respiratorio agudo / Prone position in patients with acute respiratory distress syndrome

RESUMEN El síndrome de distrés respiratorio agudo ocupa gran atención en la unidad de cuidados intensivos. A pesar del amplio conocimiento alcanzado sobre la fisiopatología de éste síndrome, el enfoque en la unidad de cuidados intensivos consiste, en gran parte, en un tratamiento de soporte vital y en evitar los efectos secundarios de las terapéuticas invasivas. Si bien, durante los últimos 20 años, se generaron grandes avances en ventilación mecánica con un impacto importante sobre la mortalidad, ésta continúa siendo elevada. Una característica de los pacientes con síndrome de distrés respiratorio agudo, sobre todo los más severos, es la presencia de hipoxemia refractaria debido a la existencia de shunt, pudiendo requerir tratamientos adicionales a la ventilación mecánica, entre ellos la ventilación mecánica en decúbito prono. Este método, recomendado para mejorar la oxigenación por primera vez en 1974, puede ser implementado fácilmente en cualquier unidad de cuidados intensivos con personal entrenado. El decúbito prono tiene un sustento bibliográfico sumamente robusto. Varios ensayos clínicos randomizados han demostrado el efecto del decúbito prono sobre la oxigenación en pacientes con síndrome de distrés respiratorio agudo medida a través de la relación PaO2/FiO2 e incluso su impacto en el aumento de la sobrevida de estos pacientes. Los integrantes del Comité de Kinesiología Intensivista de la Sociedad Argentina de Terapia Intensiva realizaron una revisión narrativa con el objetivo de exponer la evidencia disponible en relación a la implementación del decúbito prono, los cambios producidos en el sistema respiratorio por la aplicación de la maniobra y su impacto sobre la mortalidad. Por último, se sugerirán lineamientos para la toma de decisiones.

ABSTRACT Acute respiratory distress syndrome occupies a great deal of attention in intensive care units. Despite ample knowledge of the physiopathology of this syndrome, the focus in intensive care units consists mostly of life-supporting treatment and avoidance of the side effects of invasive treatments. Although great advances in mechanical ventilation have occurred in the past 20 years, with a significant impact on mortality, the incidence continues to be high. Patients with acute respiratory distress syndrome, especially the most severe cases, often present with refractory hypoxemia due to shunt, which can require additional treatments beyond mechanical ventilation, among which is mechanical ventilation in the prone position. This method, first recommended to improve oxygenation in 1974, can be easily implemented in any intensive care unit with trained personnel. Prone position has extremely robust bibliographic support. Various randomized clinical studies have demonstrated the effect of prone decubitus on the oxygenation of patients with acute respiratory distress syndrome measured in terms of the PaO2/FiO2 ratio, including its effects on increasing patient survival. The members of the Respiratory Therapists Committee of the Sociedad Argentina de Terapia Intensiva performed a narrative review with the objective of discovering the available evidence related to the implementation of prone position, changes produced in the respiratory system due to the application of this maneuver, and its impact on mortality. Finally, guidelines are suggested for decision-making.

Síndrome de distrés respiratorio agudo en pediatría / Pediatric acute respiratory distress syndrome

The Acute Respiratory Distress Syndrome (ARDS) is a life-threatening disease with a high mortality rate. In children it represents a diagnostic and therapeutic challenge. The primary feature in the development of ARDS is the non-cardiogenic pulmonary edema resulting from a disproportionate inflammatory response that increases the blood-gas barrier permeability. There is strong evidence that aninappropriate ventilatory support may induce lung injury, organ dysfunction and increasing mortality.The aim of this article is to review current concepts related to the diagnostic of pediatric ARDS, its pathophysiologic mechanisms, ventilator induced lung injury and a brief description of rescue therapies.

El Síndrome de Distrés Respiratorio Agudo (SDRA) es una entidad grave de elevada mortalidad, siendo en pediatría un desafío diagnóstico y terapéutico. La característica primaria del SDRA es el desarrollo de edema pulmonar no cardiogénico debido a una respuesta inflamatoria excesiva que aumenta la permeabilidad de la barrera sangre-gas. Existe una fuerte evidencia de que una estrategia inadecuada de soporte ventilatorio puede aumentar el daño pulmonar, inducir disfunciones de َrganos a distancia y aumentar la mortalidad.El presente artيculo pretende revisar conceptos actuales relacionados al diagnóstico de SDRA pediátrico, mecanismos fisiopatológicos, daño pulmonar inducido por la ventilación mecánica y una breve revisión de las terapias de rescate.

Progressos e perspectivas na síndrome do desconforto respiratório agudo em pediatria / Progress and perspectives in pediatric acute respiratory distress syndrome

RESUMOA síndrome do desconforto respiratório agudo é uma patologia de início agudo, marcada por hipoxemia e infiltrados na radiografia de tórax, acometendo tanto adultos quanto crianças de todas as faixas etárias. Ela é causa importante de insuficiência respiratória em unidades de terapia intensiva pediátrica associada a significativa morbidade e mortalidade. Apesar disso, até recentemente, as definições e os critérios diagnósticos para síndrome do desconforto respiratório agudo centravam-se na população adulta. No presente artigo, revisamos a evolução da definição da síndrome do desconforto respiratório agudo ao longo de quase cinco décadas, com foco especial na nova definição pediátrica. Discutimos ainda recomendações relativas à aplicação de estratégias de ventilação mecânica no tratamento da síndrome do desconforto respiratório agudo em crianças, assim como o uso de terapias adjuvantes.

ABSTRACTAcute respiratory distress syndrome is a disease of acute onset characterized by hypoxemia and infiltrates on chest radiographs that affects both adults and children of all ages. It is an important cause of respiratory failure in pediatric intensive care units and is associated with significant morbidity and mortality. Nevertheless, until recently, the definitions and diagnostic criteria for acute respiratory distress syndrome have focused on the adult population. In this article, we review the evolution of the definition of acute respiratory distress syndrome over nearly five decades, with a special focus on the new pediatric definition. We also discuss recommendations for the implementation of mechanical ventilation strategies in the treatment of acute respiratory distress syndrome in children and the use of adjuvant therapies.

Pulmonary hypertension due to acute respiratory distress syndrome

Our aims were to describe the prevalence of pulmonary hypertension in patients with acute respiratory distress syndrome (ARDS), to characterize their hemodynamic cardiopulmonary profiles, and to correlate these parameters with outcome. All consecutive patients over 16 years of age who were in the intensive care unit with a diagnosis of ARDS and an in situ pulmonary artery catheter for hemodynamic monitoring were studied. Pulmonary hypertension was diagnosed when the mean pulmonary artery pressure was >25 mmHg at rest with a pulmonary artery occlusion pressure or left atrial pressure <15 mmHg. During the study period, 30 of 402 critically ill patients (7.46%) who were admitted to the ICU fulfilled the criteria for ARDS. Of the 30 patients with ARDS, 14 met the criteria for pulmonary hypertension, a prevalence of 46.6% (95% CI; 28-66%). The most common cause of ARDS was pneumonia (56.3%). The overall mortality was 36.6% and was similar in patients with and without pulmonary hypertension. Differences in patients' hemodynamic profiles were influenced by the presence of pulmonary hypertension. The levels of positive end-expiratory pressure and peak pressure were higher in patients with pulmonary hypertension, and the PaCO2 was higher in those who died. The level of airway pressure seemed to influence the onset of pulmonary hypertension. Survival was determined by the severity of organ failure at admission to the intensive care unit.

Postperfusion lung syndrome: physiopathology and therapeutic options / Síndrome pós-perfusão pulmonar: fisiopatologia e opções terapêuticas

Postperfusion lung syndrome is rare but can be lethal. The underlying mechanism remains uncertain but triggering inflammatory cascades have become an accepted etiology. A better understanding of the pathophysiology and the roles of inflammatory mediators in the development of the syndrome is imperative in the determination of therapeutic options and promotion of patients' prognosis and survival. Postperfusion lung syndrome is similar to adult respiratory distress syndrome in clinical features, diagnostic approaches and management strategies. However, the etiologies and predisposing risk factors may differ between each other. The prognosis of the postperfusion lung syndrome can be poorer in comparison to acute respiratory distress syndrome due to the secondary multiple organ failure and triple acid-base imbalance. Current management strategies are focusing on attenuating inflammatory responses and preventing from pulmonary ischemia-reperfusion injury. Choices of cardiopulmonary bypass circuit and apparatus, innovative cardiopulmonary bypass techniques, modified surgical maneuvers and several pharmaceutical agents can be potential preventive strategies for acute lung injury during cardiopulmonary bypass.

Síndrome pós-perfusão pulmonar é rara, mas pode ser letal. O mecanismo subjacente permanece incerto, mas desencadear cascatas inflamatórias tornou-se uma etiologia aceita. É imperativo uma melhor compreensão da fisiopatologia e os papéis de mediadores inflamatórios no desenvolvimento da síndrome na determinação de opções terapêuticas e de promoção do prognóstico e sobrevida dos pacientes. Síndrome pós-perfusão pulmonar é semelhante à síndrome da angústia respiratória do adulto em características clínicas, métodos diagnósticos e estratégias de gestão. No entanto, as etiologias e fatores de risco predisponentes podem ser diferentes entre si. O prognóstico da síndrome pós-perfusão pulmonar pode ser mais pobres em comparação com síndrome da angústia respiratória aguda, devido à falência de múltiplos órgãos secundária e desequilíbrio ácido-base triplo. Estratégias de gestão atuais centram-se em atenuar reações inflamatórias e impedir lesão pulmonar de isquemia-reperfusão. Escolhas do circuito de circulação extracorpórea e aparelhos, técnicas inovadoras de circulação extracorpórea, manobras cirúrgicas modificadas e vários agentes farmacêuticos podem ser potenciais estratégias preventivas para lesão pulmonar aguda durante a circulação extracorpórea.

Efeito econômico do uso da oxigenação extracorpórea para suporte de pacientes adultos com insuficiência respiratória grave no Brasil: uma análise hipotética / The economic effect of extracorporeal membrane oxygenation to support adults with severe respiratory failure in Brazil: a hypothetical analysis

Objetivo: Analisar o custo-utilidade do uso da oxigenação extracorpórea para pacientes com síndrome da angústia respiratória aguda grave no Brasil. Métodos: Com bancos de dados de estudos previamente publicados, foi construída uma árvore encadeada de decisões. Os custos foram extraídos da média de 3 meses do preço pago pelo Sistema Único de Saúde em 2011. Com 10 milhões de pacientes simulados com desfechos e custos predeterminados, uma análise da relação de incremento de custo e de anos de vida ganhos ajustados pela qualidade (custo-utilidade) foi realizada com sobrevida de 40 e 60% dos pacientes que usaram oxigenação extracorpórea. Resultados: A árvore de decisões resultou em 16 desfechos com técnicas diferentes de suporte à vida. Com a sobrevida de 40/60%, respectivamente, o incremento de custos foi de R$ -301,00/-14,00, com o preço pago de R$ -30.913,00/-1.752,00 por ano de vida ganho ajustado pela qualidade para 6 meses e de R$ -2.386,00/-90,00 por ano de vida ganho ajustado pela qualidade até o fim de vida, quando se analisaram todos os pacientes com síndrome da angústia respiratória aguda grave. Analisando somente os pacientes com hipoxemia grave (relação da pressão parcial de oxigênio no sangue sobre a fração inspirada de oxigênio <100mmHg), o incremento de custos foi de R$ -5.714,00/272,00, com preço por ano de vida ganho ajustado pela qualidade em 6 meses de R$ -9.521,00/293,00, e com o custo de R$ -280,00/7,00 por ano de vida ganho ajustado pela qualidade. Conclusão: A relação de custo-utilidade do uso da oxigenação extracorpórea no Brasil foi potencialmente aceitável neste estudo hipotético. .

Objective: To analyze the cost-utility of using extracorporeal oxygenation for patients with severe acute respiratory distress syndrome in Brazil. Methods: A decision tree was constructed using databases from previously published studies. Costs were taken from the average price paid by the Brazilian Unified Health System (Sistema Único de Saúde; SUS) over three months in 2011. Using the data of 10,000,000 simulated patients with predetermined outcomes and costs, an analysis was performed of the ratio between cost increase and years of life gained, adjusted for quality (cost-utility), with survival rates of 40 and 60% for patients using extracorporeal membrane oxygenation. Results: The decision tree resulted in 16 outcomes with different life support techniques. With survival rates of 40 and 60%, respectively, the increased costs were R$=-301.00/-14.00, with a cost of R$=-30,913.00/-1,752.00 paid per six-month quality-adjusted life-year gained and R$=-2,386.00/-90.00 per quality-adjusted life-year gained until the end of life, when all patients with severe ARDS were analyzed. Analyzing only patients with severe hypoxemia (i.e., a ratio of partial oxygen pressure in the blood to the fraction of inspired oxygen <100mmHg), the increased cost was R$=-5,714.00/272.00, with a cost per six-month quality-adjusted life-year gained of R$=-9,521.00/293.00 and a cost of R$=-280.00/7.00 per quality-adjusted life-year gained. Conclusion: The cost-utility ratio associated with the use of extracorporeal membrane oxygenation in Brazil is potentially acceptable according to this hypothetical study. .

Manejo de la falla respiratoria catastrófica en el adulto / Management of the catastrophic respiratory failure

El SDRA severo es un síndrome clínico de relativa frecuencia en las unidades críticas y de elevada morbi-mortalidad, la que no ha sido modificada significativamente a pesar de los avances en la investigación clínica. Un conocimiento profundo de su fisiopatología y las condiciones particulares de cada caso permiten un manejo adecuado. Un número importante de estrategias de manejo han sido investigadas, con variable resultado, pero es improbable que una sola de ellas conduzca a resultados clínicos exitosos. Al revés, una combinación juiciosa e informada de las diferentes alternativas terapéuticas disponibles es la única opción conocida hoy día para el manejo de estos pacientes. La transferencia precoz de estos casos a centros de referencia con experiencia y equipamiento en el manejo de esta patología puede salvar vidas.

Severe ARDS is a relatively common clinical syndrome in critical care units and carries a high morbi-mortality, which has not been significantly modified despite advances in clinical research. A thorough understanding of its pathophysiology and the particular conditions of each case allow proper management. A significant number of therapeutical strategies has been investigated, with variable results, but it is unlikely that one of them alone leads to successful clinical outcomes. Conversely, an informed and judicious combination of the different therapeutic options available is the only strategy known today for the management of this patients. An early referral of this cases to centers with expertise and equipment in the management of this disease can save lives.

Diferenças entre as formas pulmonares e extrapulmonares da síndrome do desconforto respiratório agudo / Comparison between pulmonary and extrapulmonary forms of acute respiratory distress syndrome

A síndrome do desconforto respiratório agudo (SDRA) pode ser causada por uma lesão direta (pulmonar) e/ou indireta (extrapulmonar) ao parênquima pulmonar. O presente estudo teve como objetivo apresentar uma revisão das principais diferenças entre a SDRA pulmonar e a SDRA extrapulmonar, discutindo os aspectos morfofuncionais e a resposta às diferentes estratégias terapêuticas. Esta revisão teve como base uma pesquisa bibliográfica sistemática de artigos clínicos e experimentais sobre a SDRA incluídos nas bases de dados Medline e SciELO. Com base em estudos experimentais, pode-se afirmar que a SDRA pulmonar e a SDRA extrapulmonar não são idênticas no que diz respeito a fisiopatologia, morfologia, mecânica respiratória e resposta às estratégias terapêuticas ventilatórias (pressão expiratória final positiva, manobras de recrutamento e posicionamento) e farmacológicas. Entretanto, os resultados dos estudos clínicos são contraditórios. Isso pode ser atribuído à dificuldade de se classificar a SDRA em pulmonar ou extrapulmonar, à coexistência de mais de um tipo de insulto, assim como a diferenças em relação à fase e à gravidade da SDRA nos pacientes. Concluindo, os pacientes com SDRA pulmonar e SDRA extrapulmonar, embora sejam portadores de síndromes diferentes, continuam sendo tratados da mesma forma. Considera-se fundamental uma melhor compreensão acerca da SDRA para melhor direcionar as estratégias terapêuticas.

The definition of acute respiratory distress syndrome (ARDS) was simplified at the 1998 American-European Consensus Conference of 1998 and now includes the following: bilateral pulmonary infiltrates; arterial oxygen tension/fraction of inspired oxygen < 200 mmHg; and pulmonary capillary wedge pressure < 18 mmHg or no signs of left heart failure.Recently, tomography and other imaging methods have allowed the chest to be analyzed in greater detail, thereby leading to a more complex understanding of ARDS. The use of genetic markers and biomarkers in plasma and bronchoalveolar lavage could lead to earlier ARDS diagnosis, thereby improving prognosis. The introduction of automatic diagnostic screening, together with the analysis of risk factors and prognostic factors associated with the syndrome, will deepen the understanding of ARDS, improving treatment and potentially reducing the associated mortality rates.

Follow-up after acute respiratory distress syndrome caused by influenza a (H1N1) virus infection

BACKGROUND: There are no reports on the long-term follow-up of patients with swine-origin influenza A virus infection that progressed to acute respiratory distress syndrome. METHODS: Four patients were prospectively followed up with pulmonary function tests and high-resolution computed tomography for six months after admission to an intensive care unit. RESULTS: Pulmonary function test results assessed two months after admission to the intensive care unit showed reduced forced vital capacity in all patients and low diffusion capacity for carbon monoxide in two patients. At six months, pulmonary function test results were available for three patients. Two patients continued to have a restrictive pattern, and none of the patients presented with abnormal diffusion capacity for carbon monoxide. All of them had a diffuse ground-glass pattern on high-resolution computed tomography that improved after six months. CONCLUSIONS: Despite the marked severity of lung disease at admission, patients with acute respiratory distress syndrome caused by swine-origin influenza A virus infection presented a late but substantial recovery over six months of follow-up.

Mechanical ventilation and volutrauma: study in vivo of a healthy pig model

Mechanical ventilation is essential in intensive care units. However, it may itself induce lung injury. Current studies are based on rodents, using exceptionally large tidal volumes for very short periods, often after a "priming" pulmonary insult. Our study deepens a clinically relevant large animal model, closely resembling human physiology and the ventilator setting used in clinic settings. Our aim was to evaluate the pathophysiological mechanisms involved in alveolo/capillary barrier damage due to mechanical stress in healthy subjects. We randomly divided 18 pigs (sedated with medetomidine/tiletamine-zolazepam and anesthetised with thiopental sodium) into three groups (n=6): two were mechanically ventilated (tidal volume of 8 or 20 ml/kg), the third breathed spontaneously for 4 hours, then animals were sacrificed (thiopental overdose). We analyzed every 30' hemogasanalysis and the main circulatory and respiratory parameters. Matrix gelatinase expression was evaluated on bronchoalveolar lavage fluid after surgery and before euthanasia. On autoptic samples we performed zymographic analysis of lung, kidney and liver tissues and histological examination of lung. Results evidenced that high Vt evoked profound alterations of lung mechanics and structure, although low Vt strategy was not devoid of side effects, too. Unexpectedly, also animals that were spontaneously breathing showed a worsening of the respiratory functions.

Efeito de diferentes técnicas de ventilação mecânica sobre o estresse oxidativo pulmonar induzido por lesão pulmonar aguda experimental / Effect of different techniques of mechanical ventilation on pulmonary oxidative stress induced by experimental acute lung lesion

Ventilação mecânica (VM) pode induzir estresse oxidativo pulmonar, o qual desempenha papel importante na lesão pulmonar. Este estudo comparou a ventilação mecânica convencional proterora (VMC) e a ventilação oscilatória de alta frequência (VAF) quanto a oxigenação, estresse oxidativo pulmonar, inflamação e lesão pulmonar histopatológica em modelo de lesão pulmonar aguda (LPA) em coelhos. Coelhos (n = 30) foram ventilados com FiO2 1.0. A lesão pulmonar foi induzida por infusão traqueal de solução salina (30mL/kg, 38 ºC). Os animais foram aleatoriamente distribuidos para compor os seguintes grupos: a) Controle [GC: volume corrente (VT) 6mL/kg, pressão expiratória final positiva (PEEP) 5cmH2O, frequência respiratória (FR) 40 ipm], b) LPA + VMC [GVMC: VT 6ml / kg, PEEP 10cmH2O, FR 40 ipm] e c) LPA + VAF [GVAF: pressão média de vias aéreas (Paw) 14 cmH2O, FR 10Hz]. Estresse oxidativo pulmonar foi avaliado por meio da capacidade antioxidante total, a resposta inflamatória pelo número de leucócitos polimorfonucleares/lavado broncoalveolar/pulmão e o dano histológico pulmonar foi quantificado por um escore. Parâmetros ventilatórios e hemodinâmicos foram registrados a cada 30 minutos. Ambos os grupos com LPA apresentaram piora da oxigenação após a indução da lesão pulmonar...

Estresse oxidativo como evento determinante na síndrome do desconforto respiratório agudo / Oxidative stress as determinant event acute respiratory distress syndrome

A lesão pulmonar aguda e sua forma mais grave, a síndrome do desconforto respiratório agudo (SDRA), são complicações frequentes em pacientes internados em unidades de terapia intensiva, sendo responsáveis pela alta mortalidade e morbidade. Embora seja considerada uma doença multifatorial, a presença do estresse oxidativo é denominador comum e determinante no mecanismo de lesão. A maioria dos estudos experimentais confirma a importância do estresse oxidativo na patogênese da SDRA. Novas estragégias terapêuticas vêm sendo tentadas, com base nos estudos clínicos e experimentais sobre patogênese da síndrome. O artigo destaca o papel do estresse oxidativo na patogênese da síndrome, por meio de apresentação dos mais recentes estudos na área. O texto objetiva também a desmistificação do tema estresse oxidativo apresentando definições e conceitos básicos.

Acute lung injury (ALI) and its most severe form, the acute respiratory distress syhdrome (ARDS), are frequent complications in critically ill patients and are responsible for significant morbidity and mortality. Although ALI and ARDS appears to be multilfactorial, a common denominator to most of the proposed mechanisms is the cellular damage mediated by oxidative stress. Evidence of oxidative stress and injury are common to most experimental models of lung injury and are corroborated in studies of patients with ALI/ARDS, underscoring the physiologic importance of these processes. New therapies strategies have been proposed based on clinical and experimental research results. The article approaches the role of oxidative stress on ALI/ARDS and also presents the main concepts of free radicals and antioxidants.

High-frequency oscillatory ventilation for acute respiratory distress syndrome.

Objective. To evaluate the effectiveness of HFOV in pediatric patients with acute respiratory distress syndrome. Methods. In this retrospective study, we reviewed all 20 pediatric patients, who were consecutively ventilated with HFOV in the pediatric intensive care unit of a tertiary medical center, from January 2006 to February 2007. Results. A total of 20 patients were enrolled. The median age of the subjects was 70 (3-168) months; 10 were male. All patients received conventional ventilation before HFOV. After initiation of HFOV, there was an immediate and sustained increase in PaO2/FiO2 ratio. The PaO2/FiO2 ratio was elevated and OI was decreased significantly after 10-20 minutes and maintained for at least 48 hours (p= 0.03, both). Thirteen of the 20 patients were successfully weaned. No significant change in the mean arterial pressure and heart rate was noted after HFOV. Overall survival rate was 65%. Of 20 patients, 11 patients suffered from extrapulmonary ARDS (ARDSexp) and 9 from pulmonary ARDS (ARDSp). When HFOV was initiated, there was significant increase in PaO2/FiO2 and decrease in OI in ARDSexp compared to ARDSp (p= 0.03, both). Also mortality rate was significantly lower in patients with ARDSexp (9% vs.66%), (p= 0.01). Conclusion. In our study, HFOV was effective in oxygenation and seems to be safe for pediatric ARDS patients. HFOV affected ARDSp and ARDSexp paediatric patients differently. However prospective, randomized controlled trials are needed to identify its benefits over conventional modes of mechanical ventilation.