Bronchoalveolar lavage recovery rate and cells.

Harmful effects of mechanical ventilation with large tidal volumes, volutrauma, may contribute much to diffuse acute lung injury. Extracellular vesicles have been noted in the context of vital organ injury. We hypothesized that extracellular vesicles from acutely injured lung can be found in both lung and blood. In a two-hit experimental porcine model, we tested if extracellular vesicles could be detected in bronchoalveolar lavage fluid and in plasma over a six-hour period of large tidal volume ventilation after surfactant depletion. After 2 hours of volutrauma, bronchoalveolar lavage fluid showed increased levels of extracellular vesicles containing nucleic acids (stained by SYTO 13) and those positive for both SYTO 13 and HMGB1. No such increase was detected in plasma at any timepoint during the six-hour experiments. This shows that nucleic acid-containing extracellular vesicles appear to be involved in progression of lung injury, possibly indicating cellular damage, but their potential to serve as diagnostic biomarkers of acute lung injury progression, based on plasma sampling, and in the very early phase, is not confirmed by these findings.

大潮气量机械通气所引发的有害效应——容积伤（volutrauma）——或在很大程度上参与诱发弥漫性急性肺损伤。细胞外囊泡（extracellular vesicles）已被证实于重要脏器损伤场景中存在。本研究提出假说：源自急性损伤肺组织的细胞外囊泡，可同时在肺组织与血液中被检出。本研究采用双打击实验猪模型，在表面活性物质耗竭后，于大潮气量通气的6小时周期内，检测支气管肺泡灌洗液与血浆中的细胞外囊泡水平。在容积伤诱导2小时后，支气管肺泡灌洗液中携带核酸（经SYTO 13染色）的细胞外囊泡，以及同时呈SYTO 13与高迁移率族蛋白B1（HMGB1）阳性的细胞外囊泡水平均出现升高。在6小时实验的全部时间点中，血浆均未检出此类囊泡水平的升高。本研究结果表明，携带核酸的细胞外囊泡似乎参与了肺损伤的进展过程，或可反映细胞损伤状态；但上述发现并未证实，基于血浆采样且针对极早期阶段的细胞外囊泡，可作为急性肺损伤进展的诊断生物标志物。