Mechanisms underlying gas exchange alterations in an experimental model of pulmonary embolism

The aim of the present study was to determine the ventilation/perfusion ratio that contributes to hypoxemia in pulmonary embolism by analyzing blood gases and volumetric capnography in a model of experimental acute pulmonary embolism. Pulmonary embolization with autologous blood clots was induced in seven pigs weighing 24.00 ± 0.6 kg, anesthetized and mechanically ventilated. Significant changes occurred from baseline to 20 min after embolization, such as reduction in oxygen partial pressures in arterial blood (from 87.71 ± 8.64 to 39.14 ± 6.77 mmHg) and alveolar air (from 92.97 ± 2.14 to 63.91 ± 8.27 mmHg). The effective alveolar ventilation exhibited a significant reduction (from 199.62 ± 42.01 to 84.34 ± 44.13) consistent with the fall in alveolar gas volume that effectively participated in gas exchange. The relation between the alveolar ventilation that effectively participated in gas exchange and cardiac output (V Aeff/Q ratio) also presented a significant reduction after embolization (from 0.96 ± 0.34 to 0.33 ± 0.17 fraction). The carbon dioxide partial pressure increased significantly in arterial blood (from 37.51 ± 1.71 to 60.76 ± 6.62 mmHg), but decreased significantly in exhaled air at the end of the respiratory cycle (from 35.57 ± 1.22 to 23.15 ± 8.24 mmHg). Exhaled air at the end of the respiratory cycle returned to baseline values 40 min after embolism. The arterial to alveolar carbon dioxide gradient increased significantly (from 1.94 ± 1.36 to 37.61 ± 12.79 mmHg), as also did the calculated alveolar (from 56.38 ± 22.47 to 178.09 ± 37.46 mL) and physiological (from 0.37 ± 0.05 to 0.75 ± 0.10 fraction) dead spaces. Based on our data, we conclude that the severe arterial hypoxemia observed in this experimental model may be attributed to the reduction of the V Aeff/Q ratio. We were also able to demonstrate that V Aeff/Q progressively improves after embolization, a fact attributed to the alveolar ventilation redistribution induced by hypocapnic bronchoconstriction.

Diagnostic investigation of ventilator-associated pneumonia using bronchoalveolar lavage: comparative study with a postmortem lung biopsy

The purpose of the present study was to validate the quantitative culture and cellularity of bronchoalveolar lavage (BAL) for the diagnosis of ventilator-associated pneumonia (VAP). A prospective validation test trial was carried out between 1992 and 1997 in a general adult intensive care unit of a teaching hospital. Thirty-seven patients on mechanical ventilation with suspected VAP who died at most three days after a BAL diagnostic procedure were submitted to a postmortem lung biopsy. BAL effluent was submitted to Gram staining, quantitative culture and cellularity count. Postmortem lung tissue quantitative culture and histopathological findings were considered to be the gold standard exams for VAP diagnosis. According to these criteria, 20 patients (54 percent) were diagnosed as having VAP and 17 (46 percent) as not having the condition. Quantitative culture of BAL effluent showed 90 percent sensitivity (18/20), 94.1 percent specificity (16/17), 94.7 percent positive predictive value and 88.8 percent negative predictive value. Fever and leukocytosis were useless for VAP diagnosis. Gram staining of BAL effluent was negative in 94.1 percent of the patients without VAP (16/17). Regarding the total cellularity of BAL, a cut-off point of 400,000 cells/ml showed a specificity of 94.1 percent (16/17), and a cut-off point of 50 percent of BAL neutrophils showed a sensitivity of 90 percent (19/20). In conclusion, BAL quantitative culture, Gram staining and cellularity might be useful in the diagnostic investigation of VAP

Ultra-estrutura pulmonar e circulacao extracorporea. / Pulmonary ultrastructure and extra-corporal circulation

Com a finalidade de observar o efeito da circulacao extracorporea sobre a ultra-estrutura pulmonar, foram estudados 12 doentes submetidos a cirurgia cardiaca, com um tempo de perfusao de ate 60 minutos. Nao observamos, a microscopia eletronica, as alteracoes degenerativas classicas descritas na literatura

"Atrioseptoplastia" para a correção de comunicação interatrial do tipo seio venoso com drenagem anômala de veia pulmonar em cava superior / Atrioseptoplasty for correction of interatrial defect of the venous sinus type with anomalous drainage of pulmonary vein in the superior vena cava

Descreve-se a tecnica da "atrioseptoplastia" para a correcao da comunicacao interatrial do tipo seio venoso com drenagem anomala de veia pulmonar em cava superior.Um retalho de parede anterior do atrio direito e utilizado para fechar o defeito septal desviando, simultaneamente, o fluxo da veia pulmonar para o atrio esquerdo. Um retalho de pericardio com tamanho e forma adequados e empregado para reconstruir o atrio de pericardio com tamanho e forma adequados e empregado para reconstruir o atrio direito e a veia cava superior. Dois pacientes portadores deste tipo de anomalia congenita foram operados por esta tecnica. Os resultados imediatos foram satisfatorios. Ressalta-se a simplicidade do procedimento e a facilidade de sua execucao

Efeitos da esterilizacao da dura-mater humana pelo oxido de etileno. / Effects of the sterilization of human dura-mater by ethylene oxyde

Segmentos de dura-mater, destinados a confeccao de valvas cardiacas, condicionados em glicerina a 95,5%, foram submetidos a esterilizacao pelo oxido de etileno em autoclave a duas atmosferas de pressao, por um periodo de 12 horas seguidas por 72 horas de aeracao. O oxido de etileno foi utilizado em mistura com gas carbonico na proporcao de 20% para o primeiro e 80% para o ultimo. Culturas em meios apropriados para bacterias e fungos foram negativas para controles ate 180 dias de estoque. A medida de pressao de ruptura foi utilizada para verificar eventual alteracao das caracteristicas fisicas, resultante do metodo de esterilizacao empregado. A analise dos dados obtidos, comparados aos de uma serie de controle, nao mostrou diferenca estatisticamente significante. Os autores concluem pela eficiencia do metodo empregado de esterilizacao da dura-mater humana pelo oxido de etileno e que o mesmo nao altera, de imediato, as caracteristicas fisicas do tecido. A proposicao de se adotar esse metodo, como rotina na esterilizacao de valvas cardiacas de dura-mater, deve aguardar os resultados clinicos em uma serie de pacientes em observacao