Surgery
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The objective of this study was to define the response of extravascular lung water (EVLW) to different levels of positive end-expiratory pressure (PEEP) following a standardized oleic acid injury to the lung. All animals responded to the injection of intravenous oleic acid by the rapid development of hypoxemia. There was a twofold increase in EVLW during the first 3 hours after oleic acid injection which remained stable during the remainder of the experiment, including periods on PEEP. ⋯ This was due to the decrease in cardiac output that more than offset the effects of a diminished Qs/Qt with PEEP. This study indicates that the mechanism by which PEEP improves oxygenation does not appear to be mediated by effect on lung water. The study also emphasizes the importance of determining oxygen transport when managing patients on PEEP.
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The reticuloendothelial system (RES) is thought to ensure organ integrity following trauma, burn, and sepsis by removing potentially embolic particulate matter and blood-borne bacteria from the circulation. Blockade of the RES with foreign colloids is known to result in a consumptive depletion of opsonic fibronectin, which modulates reticuloendothelial function, and an increase in lung localization of test particles. We investigated the role of neutrophils as a contributing factor in the increased localization of blood-borne bacteria in the lung after blockade. ⋯ Experimentally induced neutropenia abrogated the effect of colloid injection on lung localization of bacteria. It is concluded that a particulate load results in simultaneous RE blockade and neutrophil margination in the lung, both of which contribute to the increase in lung localization of bacteria. A mechanism for neutrophil-mediated pulmonary injury related to RE dysfunction following trauma is proposed.