PURPOSE: To assess the efficacy of an adjustable inspiratory occlusion valve in experimental bronchopleural fistula during mechanical ventilation.METHODS:We studied six mechanically ventilated pigs in a surgically created, reproducible model of bronchopleural fistula managed with mechanical ventilation and water-sealed thoracic drainage. An adjustable inspiratory occlusion valve was placed between the thoracic drain and the endotracheal tube. Hemodynamic data, capnography and blood gases were recorded before and after the creation of the bronchopleural fistula as well as after every adjustment of the inspiratory occlusion valve.RESULTS:When compared with the standard water-sealed drainage treatment, the use of an adjustable inspiratory occlusion valve improved the alveolar tidal volume and reduced bronchopleural air leak (p<0.001), without hemodynamic compromise when compared with conventional water sealed drainage.CONCLUSION: The use of an adjustable inspiratory occlusion valve improved the alveolar tidal volume, reduced alveolar leak, in an experimental reproducible model of bronchopleural fistula, without causing any hemodynamic derangements when compared with conventional water sealed drainage.

PURPOSE:To investigate the hemodynamic and ventilatory changes associated with the creation of an experimental bronchopleural fistula (BPF) treated by mechanical ventilation and thoracic drainage with or without a water seal.METHODS :Six large white pigs weighing 25 kg each which, after general anesthesia, underwent endotracheal intubation (6mm), and mechanically ventilation. Through a left thoracotomy, a resection of the lingula was performed in order to create a BPF with an output exceeding 50% of the inspired volume. The chest cavity was closed and drained into the water sealed system for initial observation of the high output BPF.RESULTS:Significant reduction in BPF output and PaCO2 was related after insertion of a water-sealed thoracic drain, p< 0.05.CONCLUSION: Insertion of a water-sealed thoracic drain resulted in reduction in bronchopleural fistula output and better CO2 clearance without any drop in cardiac output or significant changes in mean arterial pressure.

OBJETIVO: O presente estudo foi desenhado para identificar o efeito da pressão expiratória final positiva (PEEP) e o volume corrente pulmonar ideal para ventilar animais com fístula broncopleural produzida cirurgicamente, com o intuito de reduzir a vazão da fístula sem afetar a troca gasosa. MÉTODOS: Avaliação hemodinâmica e respiratória da troca gasosa foi obtida em cinco porcos jovens, saudáveis, da linhagem Large White, ventilados mecanicamente no modo ventilatório volume controlado com FiO2 de 0.4 e relação inspiração:expiração em torno de 1:2, com freqüência respiratória mantida em 22 cpm. A fístula broncopleural foi produzida pela ressecção da língula. Um sistema de drenagem a selo d'água foi instalado e o tórax foi hermeticamente fechado. A troca gasosa e o débito da fístula broncopleural foram medidos com animais ventilados sequencialmente com volumes correntes de 4 ml/kg, 7 ml/kg e 10 ml/Kg alternando zero de pressão expiratória final positiva (ZEEP) e PEEP de 10 cmH2O, sempre na mesma ordem. RESULTADOS: Esses dados são atribuídos à ventilação alveolar reduzida e às anormalidades da ventilação/perfusão que foram atenuadas com volumes correntes mais altos. PEEP aumentou o vazamento de ar pela fístula, mesmo com baixos volumes, de 2.0 ± 2,8mL para 31 ± 20,7mL (p= 0,006) e diminuiu a ventilação alveolar em todos os volumes correntes. A ventilação alveolar melhorou com altos volumes correntes, mas aumentou o débito da fístula (4 ml/kg - 2,0 ± 2,8mL e 10 mL/kg - 80,2 ± 43,9mL; p=0,001). Baixos volumes correntes resultaram em hipercapnia (ZEEP - 83,7± 6,9 mmHg e com PEEP 10 -93 ± 10,1mmHg) e diminuição significativa da saturação de oxigênio arterial, em torno de 84%. CONCLUSÃO: O volume corrente de 7 ml/kg com ZEEP foi considerado o melhor volume corrente, visto que, apesar da hipercapnia moderada, a saturação de oxigênio arterial é sustentada em torno de 90%. A ventilação alveolar melhora e o débito da fístula é reduzido quando comparado ao volume corrente de 10ml/Kg. Um baixo volume resulta em hipercapnia e grave dessaturação. Finalmente, em qualquer volume corrente, PEEP aumenta o débito da fístula e diminui a ventilação alveolar.

OBJECTIVES: The present study was designed to identify the effect of positive end expiratory pressure (PEEP) and the ideal pulmonary tidal volume to ventilate animals with a surgically produced bronchopleural fistula, aiming to reduce fistula output without affecting gas exchange. METHODS: Hemodynamic and respiratory assessment of gas exchange was obtained in five, healthy, young, mechanically ventilated Large White pigs under volume controlled ventilation with FiO2 of 0.4 and an inspiration:expiration ratio of 1:2, keeping respiratory rate at 22 cpm. A bronchopleural fistula was produced by resection of the lingula. Underwater seal drainage was installed and the thorax was hermetically closed. Gas exchange and fistula output were measured with the animals ventilated sequentially with tidal volumes of 4 ml/kg, 7 ml/kg and 10 ml/Kg alternating zero of positive end expiratory pressure (ZEEP) and PEEP of 10 cmH2O, always in the same order. RESULTS: These findings are attributed to reduced alveolar ventilation and ventilation/perfusion abnormalities and were attenuated with larger tidal volumes. PEEP increases air leak, even with low volume (of 2.0 ± 2.8mL to 31 ± 20.7mL; p= 0.006) and decreases alveolar ventilation in all tidal volumes. Alveolar ventilation improved with larger tidal volumes, but increased fistula output (10 mL/kg - 25.8 ± 18.3mL to 80.2 ± 43.9mL; p=0.0010). Low tidal volumes result in hypercapnia (ZEEP - Toneloto MGC, Terzi RGG, Silva WA, Moraes AC, Moreira MM 83.7± 6.9 mmHg and with PEEP 10 - 93 ± 10.1mmHg) and severely decreased arterial oxygen saturation, about of 84%. CONCLUSIONS: The tidal volume of 7 ml/Kg with ZEEP was considered the best tidal volume because, despite moderate hypercapnia, arterial oxygen saturation is sustained around 90%, alveolar ventilation improves and the fistula output is reduced when compared with a tidal volume of 10ml/Kg. A low tidal volume results in hypercapnia and severe desaturation. Finally, at any tidal volume, PEEP increases the fistula leak and decreases alveolar ventilation.