Predictive parameters for weaning from mechanical ventilation

A utilização de parâmetros preditivos para o desmame da ventilação mecânica é um tema de grande polêmica, com estudos divergindo sobre esse assunto. Independentemente da utilização desses parâmetros preditivos, o teste de respiração espontânea (TRE) é recomendado. O objetivo do presente estudo foi revisar a utilidade dos parâmetros preditivos para o desmame em adultos. Para tanto, foram pesquisadas as bases de dados Medline, LILACS e PubMed e foram selecionados artigos publicados entre 1991 e 2009, em língua inglesa ou portuguesa, utilizando-se os seguintes termos: weaning/desmame; extubation/extubação e weaning indexes/índices de desmame. A utilização da impressão clínica é uma forma inexata para predizer o desfecho do desmame. O parâmetro mais utilizado é a relação FR/volume corrente (V T), embora essa apresente resultados heterogêneos em termos de acurácia. Outros parâmetros relevantes são PImáx, pressão de oclusão nas vias aéreas (P0,1), relação P0,1/PImáx, FR, V T, volume minuto e o índice composto por complacência, FR, oxigenação e PImáx. Criado no Brasil, o índice integrativo de desmame tem mostrado alta acurácia. Embora recomendado, o TRE não é acurado, não identificando aproximadamente 15% das falhas de extubação. As principais limitações dos índices de desmame são devidas ao seu uso em populações específicas, aos pontos de cortes selecionados e a variações nas formas de mensuração. Como o TRE e a impressão clínica não têm 100% de acurácia, os parâmetros de desmame podem ser úteis, principalmente em situações nas quais o processo de decisão para o desmame é difícil.The use of predictive parameters for weaning from mechanical ventilation is a rather polemic topic, and the results of studies on this topic are divergent. Regardless of the use of these predictive parameters, the spontaneous breathing trial (SBT) is recommended. The objective of the present study was to review the utility of predictive parameters for weaning in adults. To that end, we searched the Medline, LILACS, and PubMed databases in order to review articles published between 1991 and 2009, in English or in Portuguese, using the following search terms: weaning/desmame, extubation/extubação, and weaning indexes/indices de desmame. The use of clinical impression is an inexact means of predicting weaning outcomes. The most widely used weaning parameter is the RR/tidal volume (V T) ratio, although this parameter presents heterogeneous results in terms of accuracy. Other relevant parameters are MIP, airway occlusion pressure (P0.1), the P0.1/MIP ratio, RR, V T, minute volume, and the index based on compliance, RR, oxygenation, and MIP. An index created in Brazil, the integrative weaning index, has shown high accuracy. Although recommended, the SBT is inaccurate, approximately 15% of extubation failures going unidentified in SBTs. The main limitations of the weaning indexes are related to their use in specific populations, the cut-off points selected, and variations in the types of measurement. Since the SBT and the clinical impression are not 100% accurate, the weaning parameters can be useful, especially in situations in which the decision as to weaning is difficult

Advanced Modes of Mechanical Ventilation

Advanced modes of mechanical ventilation emerged from the need for better control of the ventilator by the patient, the possibility of respiratory mechanics and respiratory drive monitoring in assisted modes and a better patient-ventilator synchrony. Volume-assured pressure support ventilation (VAPSV) has the advantage of the variable of flow pressure support ventilation (PSV) assuring tidal volume in each respiratory cycle. Proportional assist ventilation plus (PAV+) delivers assistance in proportion of inspiratory efforts while monitoring work of breathing, respiratory compliance, resistance and auto-PEEP, improving patient-ventilator asynchrony. Neurally adjusted ventilatory assist ventilation (NAVA) provides diaphragmatic electroactivity information and a better inspiratory and expiratory patient-ventilator synchrony. Adaptative support ventilation (ASV) assures a pre-set minute ventilation adjusting Pressure Support according to respiratory rate. Intellivent-ASV adds SpO2 and PETCO2 monitoring to adjust minute ventilation and PEEP/FIO2 according to lung pathology. Smart-Care ventilation provides an algorithm that decreases PSV according to patients tidal volume, respiratory rate and ETCO2 according to lung pathology and performs a spontaneous breathing trial indicating the redness for extubation. Clinical indications of advanced modes are to improve patient-ventilator synchrony and provide better respiratory monitoring in the assisted modes of mechanical ventilation

Interaction Between Intra-Abdominal Pressure and Positive-End Expiratory Pressure

OBJECTIVE: The aim of this study was to quantify the interaction between increased intra-abdominal pressure and Positive-End Expiratory Pressure. METHODS: In 30 mechanically ventilated ICU patients with a fixed tidal volume, respiratory system plateau and abdominal pressure were measured at a Positive-End Expiratory Pressure level of zero and 10 cm H2O. The measurements were repeated after placing a 5 kg weight on the patients' belly. RESULTS: After the addition of 5 kg to the patients' belly at zero Positive-End Expiratory Pressure, both intra-abdominal pressure (p<0.001) and plateau pressures (p=0.005) increased significantly. Increasing the Positive-End Expiratory Pressure levels from zero to 10 cm H2O without weight on the belly did not result in any increase in intra-abdominal pressure (p=0.165). However, plateau pressures increased significantly (p< 0.001). Increasing Positive-End Expiratory Pressure from zero to 10 cm H2O and adding 5 kg to the belly increased intra-abdominal pressure from 8.7 to 16.8 (p<0.001) and plateau pressure from 18.26 to 27.2 (p<0.001). Maintaining Positive-End Expiratory Pressure at 10 cm H2O and placing 5 kg on the belly increased intra-abdominal pressure from 12.3 +/- 1.7 to 16.8 +/- 1.7 (p<0.001) but did not increase plateau pressure (26.6+/-1.2 to 27.2 +/-1.1 -p=0.83). CONCLUSIONS: The addition of a 5kg weight onto the abdomen significantly increased both IAP and the airway plateau pressure, confirming that intra-abdominal hypertension elevates the plateau pressure. However, plateau pressure alone cannot be considered a good indicator for the detection of elevated intra-abdominal pressure in patients under mechanical ventilation using PEEP. In these patients, the intra-abdominal pressure must also be measured

Severe Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome is characterized by an increase of the permeability of the lungs’ alveolar-capillary membranes, leading to the extravasation of liquid rich in proteins inside the alveolar spaces that turns air-filled lungs into heavy high-osmotic pressure liquid-filled lungs. The consequence is the collapse of the lowermost lung regions, shunt, refractory hypoxemia, decrease in lungs’ compliance and increase in dead spaces that are more pronounced with the severity of the permeability changes of the pulmonary alveoli-capillary membrane. According to the recent Berlin definition, severe acute respiratory distress syndrome is defined by bilateral pulmonary infiltrates of recent onset (less than 1 week) in a patient with a risk factor for ARDS that has a PaO2/FIO2 equal or less than 100 with a positive end-expiratory pressure equal or more than 5 cm H2O with no evidence of cardiac failure or hypervolemia. Severe ARDS patients present a higher mortality ratio, a more difficult mechanical ventilatory support (higher airway pressures with low tidal ventilation and higher PaCO2 levels) and benefits for adjunctive ventilatory support therapy. The recommended mechanical ventilatory support in severe ARDS is with low tidal ventilation (less than 6 mL/Kg predicted body weight) with driving inspiratory pressures less than 15 cm H2O, respiratory rate sufficient to keep adequate minute ventilation and PaCO2 levels. PEEP higher than 15 cm H2O and prolonged prone position are recommended for more severe patients to improve their survival. Adjunctive recruitment maneuvers can be used to improve oxygenation and allow more homogeneous ventilation and PEEP titration. In refractory hypoxemia and especially in younger patients with prognosis, extra-corporeal veno-venous membrane oxygenation support can be used

Pathological and ultrastructural analysis of surgical lung biopsies in patients with swine-origin influenza type A/H1N1 and acute respiratory failure

BACKGROUND: Cases of H1N1 and other pulmonary infections evolve to acute respiratory failure and death when co-infections or lung injury predominate over the immune response, thus requiring early diagnosis to improve treatment. OBJECTIVE: To perform a detailed histopathological analysis of the open lung biopsy specimens from five patients with ARDS with confirmed H1N1. METHODS: Lung specimens underwent microbiologic analysis, and examination by optical and electron microscopy. Immunophenotyping was used to characterize macrophages, natural killer, T and B cells, and expression of cytokines and iNOS. RESULTS: The pathological features observed were necrotizing bronchiolitis, diffuse alveolar damage, alveolar hemorrhage and abnormal immune response. Ultrastructural analysis showed viral-like particles in all cases. CONCLUSIONS: Viral-like particles can be successfully demonstrated in lung tissue by ultrastructural examination, without confirmation of the virus by RT-PCR on nasopharyngeal aspirates. Bronchioles and epithelium, rather than endothelium, are probably the primary target of infection, and diffuse alveolar damage the consequence of the effect of airways obliteration and dysfunction on innate immunity, suggesting that treatment should be focused on epithelial repair.(CNPq) National Council for Scientific and Technological Development(FAPESP) São Paulo Research Foundatio

Avaliação semiquantitativa da biópsia pulmonar cirúrgica: valor preditivo e impacto na sobrevida de pacientes com infiltrado pulmonar difuso

PURPOSE: Surgical lung biopsy has been studied in distinct populations, mostly going beyond clinical issues to impinge upon routine histopathological diagnostic information in diffuse infiltrates; however, detailed tissue analyses have rarely been performed. The present study was designed to investigate the prognostic contribution provided by detailed tissue analysis in diffuse infiltrates. METHODS: Medical records and surgical lung biopsies from the period of 1982 to 2003 of 63 patients older than 18 years with diffuse infiltrates were retrospectively examined. Lung parenchyma was histologically divided into 4 anatomical compartments: interstitium, airways, vessels, and alveolar spaces. Histological changes throughout these anatomical compartments were then evaluated according to their acute or chronic evolutional character. A semiquantitative scoring system was applied to histologic findings to evaluate the intensity and extent of the pathological process. We applied logistic regression to predict the risk of death associated with acute and chronic histological changes and to estimate the odds ratios for each of the independent variables in the model. RESULTS: Impact on survival was found for male gender (P = 0.03), presence of diffuse alveolar damage (P = 0.001), and chronic histological changes (P = 0.0004) on biopsy. Thus, being male was associated with a slightly lower risk (O.R. = 0.18; P=0.03) of dying than being female. Death risk was increased 17 times in the presence of acute histological changes such as diffuse alveolar damage and 2.5 times in the presence of chronic histological changes. CONCLUSION: Detailed analysis of histological specimens can provide more than a nosological diagnosis: this approach can provide valuable information concerning prognosis.PROPOSIÇÃO: A biópsia pulmonar cirúrgica tem sido estudada em populações distintas, geralmente abordando aspectos histopatológicos puramente diagnósticos em infiltrados pulmonares difusos, além de dados clínicos. Contudo, análises teciduais detalhadas em tais casos têm sido pouco exploradas. O presente estudo foi delineado com o intuito de se investigar a contribuição prognóstica fornecida pela análise histológica detalhada em infiltrados difusos. MÉTODOS: Foram examinados retrospectivamente os prontuários e biópsias pulmonares cirúrgicas de 63 pacientes maiores de 18 anos, com infiltrados difusos, de 1982 a 2003. O parênquima pulmonar foi dividido em 4 compartimentos histológicos: interstício, vias aéreas, vasos e espaços alveolares. Alterações histológicas de cada compartimento histológico foram então avaliadas de acordo com seu caráter evolutivo agudo ou crônico. Um escore semiquantitativo foi aplicado a achados histopatológicos com o intuito de se avaliar a intensidade e a extensão do processo patológico. Aplicamos regressão logística para predizer o risco de morte para alterações histológicas agudas e crônicas e para estimar a razão de probabilidades para cada uma das variáveis independentes do modelo. RESULTADOS: O impacto sobre a sobrevida foi observado para o gênero masculino (p=0.03), para a presença de dano alveolar difuso (p=0.001) e para alterações histológicas crônicas (p=0.0004) em biópsias. Assim, homens apresentariam menor chance (O.R. = 0.18; P=0.03) de morrer do que mulheres. O risco de morte foi 17 vezes maior na presença de alterações histológicas agudas como dano alveolar difuso e 2,5 vezes na presença de alterações histológicas crônicas. CONCLUSÃO: A análise detalhada de espécimes histológicos pode proporcionar maiores e mais valiosas informações de valor prognóstico do que o simples diagnóstico nosológico

Ventilação mecânica na crise de asma aguda

BACKGROUND AND OBJECTIVES: The II Brazilian Consensus Conference on Mechanical Ventilation was published in 2000. Knowledge on the field of mechanical ventilation evolved rapidly since then, with the publication of numerous clinical studies with potential impact on the ventilatory management of critically ill patients. Moreover, the evolving concept of evidence - based medicine determined the grading of clinical recommendations according to the methodological value of the studies on which they are based. This explicit approach has broadened the understanding and adoption of clinical recommendations. For these reasons, AMIB – Associação de Medicina Intensiva Brasileira and SBPT – Sociedade Brasileira de Pneumologia e Tisiologia – decided to update the recommendations of the II Brazilian Consensus. Mechanical ventilation in the asthma attack has been one of the updated topics. Describe the most important topics on the mechanical ventilation during the asthma attack and suggest the main therapeutic approaches. METHODS: Systematic review of the published literature and gradation of the studies in levels of evidence, using the key words "mechanical ventilation" and "asthma". RESULTS: We present recommendations on the ventilatory modes and settings to be adopted when ventilating a patient during an asthma attack, as well as the recommended monitoring. Alternative ventilation techniques are also presented. CONCLUSIONS: Protective ventilatory strategies are recommended when ventilating a patient during a severe asthma attack.JUSTIFICATIVA E OBJETIVOS: Em 2000, foi publicado o II Consenso Brasileiro de Ventilação Mecânica. Desde então, o conhecimento na área da ventilação mecânica avançou rapidamente, com a publicação de inúmeros estudos clínicos que acrescentaram informações importantes para o manuseio de pacientes críticos em ventilação artificial. Além disso, a expansão do conceito de Medicina Baseada em Evidências (MBE) determinou a hierarquização das recomendações clínicas, segundo o rigor metodológico dos estudos que as embasaram. Essa abordagem explícita vem ampliando a compreensão e a aplicação das recomendações clínicas. Por esses motivos, a AMIB – Associação de Medicina Intensiva Brasileira – e a SBPT – Sociedade Brasileira de Pneumologia e Tisiologia – julgaram conveniente a atualização das recomendações descritas no Consenso anterior. Dentre os tópicos selecionados a Ventilação Mecânica na Crise de Asma foi um dos temas propostos. O objetivo deste estudo foi descrever os pontos mais importantes relacionados à ventilação mecânica durante a crise de asma e sugerir as principais abordagens terapêuticas. MÉTODO: Objetivou-se chegar a um documento suficientemente sintético, que refletisse a melhor evidência disponível na literatura. A revisão bibliográfica baseou-se na busca de estudos através de palavras-chave e em sua gradação conforme níveis de evidência. As palavras-chave utilizadas para a busca foram: Ventilação mecânica na asma: asthma and mechanical ventilation. RESULTADOS: São apresentadas recomendações quanto aos modos ventilatórios e aos parâmetros a serem aplicados quando do ajuste do ventilador, além da monitoração recomendada. Apresentam-se ainda, técnicas alternativas que possam ser utilizadas. CONCLUSÕES: Estratégias protetoras de ventilação mecânica são recomendadas durante a ventilação mecânica de paciente asmático grave

Mechanical Ventilation and Clinical Outcomes in Patients with Acute Myocardial Infarction: A Retrospective Observational Study

Patients with acute myocardial infarction (AMI) and respiratory impairment may be treated with either invasive or non-invasive mechanical ventilation (MV). However, there has been little testing of non-invasive MV in the setting of AMI. Our objective was to evaluate the incidence and associated clinical outcomes of patients with AMI who were treated with non-invasive or invasive MV