INTRODUÇÃO: Estudos recentes sugerem que o uso da estratégia protetora de ventilação mecânica no intra-operatório pode reduzir a incidência de complicações pulmonares pós-operatórias (CPP). O objetivo desta meta-análise de dados individuais de pacientes é avaliar o efeito independente do volume corrente e da pressão positiva ao final da expiração (PEEP) na ocorrência de CPP. MÉTODOS: Foram incluídos ensaios clínicos randomizados que compararam a estratégia protetora de ventilação mecânica com a estratégia convencional em pacientes submetidos à anestesia para cirurgia. O desfecho primário foi o desenvolvimento de CPP. Diversos fatores prognósticos pré-definidos foram testados por meio da regressão logística multivariada. RESULTADOS: Quatorze ensaios clínicos randomizados foram incluídos (2.095 pacientes). Houve 97 casos de CPP em 1.102 pacientes (8,8%) ventilados com a estratégia protetora e 148 casos em 993 pacientes (14,9%) ventilados com a estratégia convencional (risco ajustado relativo [RR], 0,64; 95% intervalo de confiança [IC], 0,46 - 0,88, p < 0,01). Houve 85 casos de CPP em 957 pacientes (8,9%) ventilados com volume corrente baixo e PEEP alto e 63 casos em 525 pacientes (12%) ventilados com volume corrente baixo e PEEP baixo (RR, 0,93; 95% CI, 0,64 - 1,37, p = 0,72). Foi encontrada uma relação de dose-resposta entre o aparecimento de CPP e o volume corrente (R2 por meio termo quadrático = 0,390), mas não entre o aparecimento de CPP e o nível de PEEP (R2 = 0,082). A manutenção de uma driving pressure inferior a 13 cmH2O durante a cirurgia está associado a menor incidência de síndrome do desconforto respiratório agudo (SDRA). CONCLUSÃO: Esta meta-análise de dados individuais suporta os efeitos benéficos da estratégia protetora de ventilação mecânica em pacientes submetidos à cirurgia e sugere que altos níveis de PEEP, na vigência de volume corrente baixo, não acrescentam benefícios / INTRODUCTION: Recent studies show that intraoperative mechanical ventilation using low tidal volumes can prevent postoperative pulmonary complications (PPC). The aim of this individual patient data meta-analysis is to evaluate the individual associations between tidal volume size and PEEP level, and occurrence of PPC. METHODS: Randomized controlled trials comparing protective ventilation and conventional ventilation in patients undergoing general surgery were screened for inclusion. The primary outcome was development of PPC. Predefined prognostic factors were tested using multivariate logistic regression. RESULTS: Fourteen randomized controlled trials were included (2095 patients). There were 97 cases of PPC in 1102 patients (8.8%) assigned to protective ventilation and 148 cases in 993 patients (14.9%) assigned to conventional ventilation (adjusted relative risk [RR], 0.64; 95% confidence interval [CI], 0.46 - 0.88; p < 0.01). There were 85 cases of PPC in 957 patients (8.9%) assigned to ventilation with low tidal volume and high PEEP levels and 63 cases in 525 patients (12%) assigned to ventilation with low tidal volume and low PEEP levels (RR, 0.93; 95% CI, 0.64 - 1.37; p = 0.72). A dose-response relationship was found between the appearance of PPC and tidal volume size (R2 for mean quadratic term = 0.390), but not between the appearance of PPC and PEEP level (R2 = 0.082). The maintenance of a driving pressure below 13 cmH2O during surgery is associated with reduced incidence of acute respiratory distress syndrome. CONCLUSION: This individual data meta-analysis supports the beneficial effects of protective ventilation settings in patients undergoing surgery and suggests no benefit from high PEEP levels with use of low tidal volume

Introdução: A tomografia de impedância elétrica (TIE) é uma técnica de imagem não invasiva que mensura o potencial elétrico na superfície torácica através de eletrodos colocados ao redor do tórax. Essas medidas são transformadas em uma imagem bidimensional da distribuição da impedância elétrica no tórax. Esse instrumento detecta modificações da densidade pulmonar e distribuição do volume corrente. Entretanto, é necessário melhor avaliação da sua eficiência em estimar o volume corrente (VT) a cada ciclo ventilatório. O objetivo do estudo é avaliar a correlação do volume estimado pela TIE com o VT aplicado durante o suporte ventilatório mecânico. Métodos: Inicialmente, foram estudados cinco suínos da raça Landrace. Os animais foram sedados, intubados e monitorados com a TIE. Foram aplicados volumes incrementais (100, 250, 500, 750 e 1000 mL) com a seringa de precisão em ZEEP e com PEEP de 5, 10 e 20 cmH2O, antes e depois da promoção de lesão pulmonar com lavagem com solução salina. Posteriormente, outros cinco animais foram monitorados com a tomografia computadorizada de tórax por raios X (TC) e a TIE. Foram aplicados volumes incrementais (250, 500 e 1000 mL) com a seringa de precisão em ZEEP e com PEEP de 10 e 20 cmH2O, também antes e depois da promoção de lesão pulmonar. A amplitude da variação de impedância mensurada pela TIE foi convertida em volume e foi calculado o volume de ar na TC. Análises de correlação e concordância foram realizadas com o programa \"R\" (© R Foundation for Statistical Computing). Resultados: Em ZEEP, o coeficiente de correlação entre os volumes estimado pela TIE e calculado pela TC foram, respectivamente, 0,90 e 0,96 na comparação com a seringa de precisão. O coeficiente de determinação entre a TIE e a seringa de precisão foi progressivamente reduzindo (0,90; 0,89 e 0,81 com PEEP de 5; 10 e 20, respectivamente) com o aumento do volume pulmonar promovido pela elevação da PEEP. A TC mostrou um deslocamento progressivo do conteúdo aéreo no sentido caudal com o aumento do volume pulmonar. Conclusões: Há uma boa correlação entre o volume estimado pela TIE e o VT aplicado durante o suporte ventilatório mecânico quando utilizados volumes e pressões usuais na prática clínica / Rationale: Electrical impedance tomography (EIT) is a noninvasive imaging tool that reconstructs a cross-sectional image of the lung\'s regional conductivity using electrodes placed circumferentially around the thorax. It is able to detect changes of lung air content and tidal volume (VT) distribution. However, better evaluation of its capacity to quantify VT variations is necessary. The aim of our study was to assess the correlation between volume estimated by EIT and tidal volume applied at different positive end-expiratory pressures (PEEP). Methods: Initially, in an experimental study five mechanically ventilated pigs monitored by EIT were studied. VT increments (100, 250, 500, 750 and 1000 mL) were applied with a calibrated syringe at zero end-expiratory pressure (ZEEP) and PEEP levels of 5, 10 and 20 cmH2O before and after lung-injury (induced by saline lavage). Another five pigs was monitored by EIT and x-ray computed tomography (CT). VT increments (250, 500 and 1000 mL) were applied with a calibrated syringe at zero end-expiratory pressure (ZEEP) and PEEP levels of 10 and 20 cmH2O before and after lung-injury. Lung air volume was calculated at CT scan and the amplitude of impedance change measured by EIT was converted to volume (mL). Correlation and agreement analysis was performed at \"R\" program (© R Foundation for Statistical Computing). Results: At ZEEP, volume estimated by EIT and volume calculated at CT obtained r2 = 0.90 and 0.96 respectively, when compared to calibrated syringe. The coefficient of correlation between EIT and calibrated syringe impaired (0.90; 0.89 and 0.81 with PEEP of 5; 10 and 20, respectively) with increase of the lung volume due to increased PEEP. CT showed a progressive displacement of the air content to the caudal thoracic levels with the increase of the lung volume. Conclusion: EIT is able to estimate tidal volume during mechanical ventilatory support when used volumes and pressures usually applied at bedside

INTRODUÇÃO: Estudos recentes sugerem que o uso da estratégia protetora de ventilação mecânica no intra-operatório pode reduzir a incidência de complicações pulmonares pós-operatórias (CPP). O objetivo desta meta-análise de dados individuais de pacientes é avaliar o efeito independente do volume corrente e da pressão positiva ao final da expiração (PEEP) na ocorrência de CPP. MÉTODOS: Foram incluídos ensaios clínicos randomizados que compararam a estratégia protetora de ventilação mecânica com a estratégia convencional em pacientes submetidos à anestesia para cirurgia. O desfecho primário foi o desenvolvimento de CPP. Diversos fatores prognósticos pré-definidos foram testados por meio da regressão logística multivariada. RESULTADOS: Quatorze ensaios clínicos randomizados foram incluídos (2.095 pacientes). Houve 97 casos de CPP em 1.102 pacientes (8,8%) ventilados com a estratégia protetora e 148 casos em 993 pacientes (14,9%) ventilados com a estratégia convencional (risco ajustado relativo [RR], 0,64; 95% intervalo de confiança [IC], 0,46 - 0,88, p < 0,01). Houve 85 casos de CPP em 957 pacientes (8,9%) ventilados com volume corrente baixo e PEEP alto e 63 casos em 525 pacientes (12%) ventilados com volume corrente baixo e PEEP baixo (RR, 0,93; 95% CI, 0,64 - 1,37, p = 0,72). Foi encontrada uma relação de dose-resposta entre o aparecimento de CPP e o volume corrente (R2 por meio termo quadrático = 0,390), mas não entre o aparecimento de CPP e o nível de PEEP (R2 = 0,082). A manutenção de uma driving pressure inferior a 13 cmH2O durante a cirurgia está associado a menor incidência de síndrome do desconforto respiratório agudo (SDRA). CONCLUSÃO: Esta meta-análise de dados individuais suporta os efeitos benéficos da estratégia protetora de ventilação mecânica em pacientes submetidos à cirurgia e sugere que altos níveis de PEEP, na vigência de volume corrente baixo, não acrescentam benefícios / INTRODUCTION: Recent studies show that intraoperative mechanical ventilation using low tidal volumes can prevent postoperative pulmonary complications (PPC). The aim of this individual patient data meta-analysis is to evaluate the individual associations between tidal volume size and PEEP level, and occurrence of PPC. METHODS: Randomized controlled trials comparing protective ventilation and conventional ventilation in patients undergoing general surgery were screened for inclusion. The primary outcome was development of PPC. Predefined prognostic factors were tested using multivariate logistic regression. RESULTS: Fourteen randomized controlled trials were included (2095 patients). There were 97 cases of PPC in 1102 patients (8.8%) assigned to protective ventilation and 148 cases in 993 patients (14.9%) assigned to conventional ventilation (adjusted relative risk [RR], 0.64; 95% confidence interval [CI], 0.46 - 0.88; p < 0.01). There were 85 cases of PPC in 957 patients (8.9%) assigned to ventilation with low tidal volume and high PEEP levels and 63 cases in 525 patients (12%) assigned to ventilation with low tidal volume and low PEEP levels (RR, 0.93; 95% CI, 0.64 - 1.37; p = 0.72). A dose-response relationship was found between the appearance of PPC and tidal volume size (R2 for mean quadratic term = 0.390), but not between the appearance of PPC and PEEP level (R2 = 0.082). The maintenance of a driving pressure below 13 cmH2O during surgery is associated with reduced incidence of acute respiratory distress syndrome. CONCLUSION: This individual data meta-analysis supports the beneficial effects of protective ventilation settings in patients undergoing surgery and suggests no benefit from high PEEP levels with use of low tidal volume

Thoracic surgical procedures require partial or complete airway separation and the opportunity to exclude one lung from ventilation (one-lung ventilation, OLV). OLV is commonly associated with profound pathophysiological changes that may affect the postoperative outcome. It is injurious in terms of increased mechanical stress including alveolar cell stretch and overdistension, shear forces secondary to repeated tidal collapse and reopening of alveolar units and compression of alveolar vessels. Ventilation and perfusion distribution may thus be affected during and after OLV. The present studies investigated the influence of OLV on ventilation and perfusion distribution, on the gas/tissue distribution and on the lung histomorphology in a pig model of thoracic surgery. Anaesthetised and mechanically ventilated piglets were examined. The ventilation and perfusion distribution within the lungs was assessed by single photon emission computed tomography. Computed tomography was used to establish the effects of OLV on dependent lung gas/tissue distribution. The pulmonary histopathology of pigs undergoing OLV and thoracic surgery was compared with that of two-lung ventilation (TLV) and spontaneous breathing. OLV induced hyperperfusion and significant V/Q mismatch in the ventilated lung persistent in the postoperative course. It increased cyclic tidal recruitment that was associated with a persistent increase of gas content in the ventilated lung. OLV and thoracic surgery as well resulted in alveolar damage.  In the present model of OLV and thoracic surgery, alveolar recruitment manoeuvre (ARM) and protective ventilation approach using low tidal volume preserved the ventilated lung density distribution and did not aggravate cyclic recruitment of alveoli in the ventilated lung. In conclusion, the present model established significant alveolar damage in response to OLV and thoracic surgery. Lung injury could be related to the profound pathophysiological consequences of OLV including hyperperfusion, ventilation/perfusion mismatch and increased tidal recruitment of lung tissue in the dependent, ventilated lung.  These mechanisms may contribute to the increased susceptibility for respiratory complications in patients undergoing thoracic surgery. A protective approach including sufficient ARM, application of PEEP, and the use of lower tidal volumes may prevent the ventilated lung from deleterious consequences of OLV.

Detection of early pathophysiological changes of breathing in children with chronic respiratory disease MD. Vaclav Koucky - Ph.D. thesis Abstract Introduction: Currently, there are different methods for infant pulmonary function testing (iPFT) and morphological assessment of microscopic changes in endobronchial biopsy samples (EBB). In research setting, they allow detection of early pathophysiological changes of breathing in small children with chronic respiratory disease, respectively in risk of its development. Their clinical significance, however, is not fully acknowledged. The aim of this thesis is to evaluate the safety, feasibility and clinical significance of iPFT and EBB in infants younger than 2 years of age. In addition, the relationship between functional and morphological changes of respiratory tract and the function of peripheral chemoreceptors was studied in selected patients' subgroups. Methods: Fifty-five infants with cystic fibrosis (CF), 35 physician-confirmed recurrent wheezers (AB), 9 infants with congenital diaphragmatic hernia, 7 with interstitial lung disease (chILD) and 3 with primary ciliary dyskinesia (PCD) were enrolled. All infants underwent iPFT and relevant clinical history data were recorded. Based on patients' age, CF group was divided into CFmalí (< 6 months) and CFvelcí (>...