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Special Feature: Oral Presentations

PFC & SURFACTANT – SECRETION AND SYNTHESIS

Rüdiger, Mario

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Perfluorocarbon (PFC) is used mainly in patients with respiratory insufficiency, that often originates from a disturbance of the pulmonary surfactant system. By filling the alveoli with PFC, alveolar collapse is prevented and gas exchange is improved. However, to wean patients from PFC, the underlying problem of disturbed endogenous pulmonary surfactant system must be solved. Therefore, it is essential to understand the effect that PFC has not only on the function, but also, synthesis and secretion of the pulmonary surfactant. Early in 1970, Ruefer showed that, after 3 hours of submersion in PFC, the content of phospholipids is not affected. Furthermore, a lavage with PFC neither reduces the pulmonary phospholipid content nor alters the incorporation of acetate and choline into the lung. In contrast to the early data, measurements of surfactant content in the bronchoalveolar lavage, after partial liquid ventilation, revealed contradictory results. Depending on the species of perfluorocarbon, the lavage fluid contained various amounts of saturated phospholipids. By using labeled choline, Steinhorn and co-worker showed that, after partial liquid ventilation, significantly more labeled choline containing phospholipids was found in the lavage and lung parenchyma than in conventionally ventilated animals. Therefore, the authors concluded that liquid ventilation leads to a significant increase in the production of phospholipids. Three different explanations were suggested: a direct effect on cellular processes, an increased secretion due to a PFC-induced alveolar stretch, or a reduced alveolar degradation of surfactant. According to data on isolated type II cells, PFC lead to an increased secretion of phospholipids. However, the synthesis of surfactant-phospholipids was slightly decreased. The exten of the effect depended on the species of PFC that was studied. In healthy rats that were on short term PLV the subsequent histological quantification of surfactant content did not show an effect on the intraalveolar or intracellular surfactant content. Summarizing the data, at present, the net effect of liquid ventilation or perfluorocarbon on the pulmonary surfactant system remains unclear. Further studies would be beneficial prior to a clinical application. One opportunity to overcome a negative effect on the endogenous surfactant system due to liquid ventilation would be the combined application of PFC and surfactant. First animal data are very promising.

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