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

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

Noninvasive ventilation immediately after extubation improves weaning outcome after acute respiratory failure: a randomized controlled trial

Abstract\ud \ud \ud \ud Introduction\ud \ud Noninvasive ventilation (NIV), as a weaning-facilitating strategy in predominantly chronic obstructive pulmonary disease (COPD) mechanically ventilated patients, is associated with reduced ventilator-associated pneumonia, total duration of mechanical ventilation, length of intensive care unit (ICU) and hospital stay, and mortality. However, this benefit after planned extubation in patients with acute respiratory failure of various etiologies remains to be elucidated. The aim of this study was to determine the efficacy of NIV applied immediately after planned extubation in contrast to oxygen mask (OM) in patients with acute respiratory failure (ARF).\ud \ud \ud \ud Methods\ud \ud A randomized, prospective, controlled, unblinded clinical study in a single center of a 24-bed adult general ICU in a university hospital was carried out in a 12-month period. Included patients met extubation criteria with at least 72 hours of mechanical ventilation due to acute respiratory failure, after following the ICU weaning protocol. Patients were randomized immediately before elective extubation, being randomly allocated to one of the study groups: NIV or OM. We compared both groups regarding gas exchange 15 minutes, 2 hours, and 24 hours after extubation, reintubation rate after 48 hours, duration of mechanical ventilation, ICU length of stay, and hospital mortality.\ud \ud \ud \ud Results\ud \ud Forty patients were randomized to receive NIV (20 patients) or OM (20 patients) after the following extubation criteria were met: pressure support (PSV) of 7 cm H2O, positive end-expiratory pressure (PEEP) of 5 cm H2O, oxygen inspiratory fraction (FiO2) ≤ 40%, arterial oxygen saturation (SaO2) ≥ 90%, and ratio of respiratory rate and tidal volume in liters (f/TV) < 105. Comparing the 20 patients (NIV) with the 18 patients (OM) that finished the study 48 hours after extubation, the rate of reintubation in NIV group was 5% and 39% in OM group (P = 0.016). Relative risk for reintubation was 0.13 (CI = 0.017 to 0.946). Absolute risk reduction for reintubation showed a decrease of 33.9%, and analysis of the number needed to treat was three. No difference was found in the length of ICU stay (P = 0.681). Hospital mortality was zero in NIV group and 22.2% in OM group (P = 0.041).\ud \ud \ud \ud Conclusions\ud \ud In this study population, NIV prevented 48 hours reintubation if applied immediately after elective extubation in patients with more than 3 days of ARF when compared with the OM group.\ud \ud \ud \ud Trial Registration number\ud \ud ISRCTN: 41524441.We thank all the physicians, physiotherapists, and nurses that took care of the patients throughout the protocol, the statisticians for the statistical analyses, and Adriana Pardini for revision of the language. This study was supported by Division of Critical Care, Hospital de Base de São José do Rio Preto, Rio Preto, SP, Brazil, and Division of Pulmonary and Critical Care Hospital das Clínicas of São Paulo Medical School, University of São Paulo, São Paulo, Brazil

Statement of Second Brazilian Congress of Mechanical Ventilarion : part I

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