Mechanical ventilation can induce or even worsen lung injury, at least in part via overdistension caused by too large volumes or too high pressures. The complement system has been suggested to play a causative role in ventilator-induced lung injury. This was a single-center prospective study investigating associations between pulmonary levels of complement activation products and two ventilator settings, tidal volume (VT) and driving pressure (ΔP), in critically ill patients under invasive ventilation. A miniature bronchoalveolar lavage (BAL) was performed for determination of pulmonary levels of C5a, C3b/c, and C4b/c. The primary endpoint was the correlation between BAL fluid (BALF) levels of C5a and VT and ΔP. Levels of complement activation products were also compared between patients with and without ARDS or with and without pneumonia. Seventy-two patients were included. Median time from start of invasive ventilation till BAL was 27 [19 to 34] hours. Median VT and ΔP before BAL were 6.7 [IQR 6.1 to 7.6] ml/kg predicted bodyweight (PBW) and 15 [IQR 11 to 18] cm H2O, respectively. BALF levels of C5a, C3b/c and C4b/c were neither different between patients with or without ARDS, nor between patients with or without pneumonia. BALF levels of C5a, and also C3b/c and C4b/c, did not correlate with VT and ΔP. Median BALF levels of C5a, C3b/c, and C4b/c, and the effects of VT and ΔP on those levels, were not different between patients with or without ARDS, and in patients with or without pneumonia. In this cohort of critically ill patients under invasive ventilation, pulmonary levels of complement activation products were independent of the size of VT and the level of ΔP. The associations were not different for patients with ARDS or with pneumonia. Pulmonary complement activation does not seem to play a major role in VILI, and not even in lung injury per se, in critically ill patients under invasive ventilation.

中文翻译：

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潮气量大小和驱动压力水平对肺补体激活的影响：一项对危重患者的观察性研究

机械通气会诱发甚至加重肺损伤，至少部分是由于体积过大或压力过高引起的过度膨胀。已经建议补体系统在呼吸机引起的肺损伤中起致病作用。这是一项单中心前瞻性研究，研究了在有创通气下的危重患者中补体激活产物的肺部水平与两种呼吸机设置、潮气量 (VT) 和驱动压 (ΔP) 之间的关联。进行微型支气管肺泡灌洗 (BAL) 以确定 C5a、C3b/c 和 C4b/c 的肺水平。主要终点是 C5a 和 VT 的 BAL 液 (BALF) 水平与 ΔP 之间的相关性。还比较了患有和不患有 ARDS 或患有和不患有肺炎的患者之间补体激活产物的水平。包括 72 名患者。从开始有创通气到 BAL 的中位时间为 27 [19 至 34] 小时。BAL 前的中位 VT 和 ΔP 分别为 6.7 [IQR 6.1 至 7.6] ml/kg 预测体重 (PBW) 和 15 [IQR 11 至 18] cm H2O。C5a、C3b/c 和 C4b/c 的 BALF 水平在患有或不患有 ARDS 的患者之间，以及患有或不患有肺炎的患者之间都没有差异。C5a 以及 C3b/c 和 C4b/c 的 BALF 水平与 VT 和 ΔP 无关。C5a、C3b/c 和 C4b/c 的中位 BALF 水平，以及 VT 和 ΔP 对这些水平的影响，在有或没有 ARDS 的患者之间以及在有或没有肺炎的患者中没有差异。在这个有创通气下的危重患者队列中，补体激活产物的肺部水平与 VT 的大小和 ΔP 的水平无关。对于 ARDS 或肺炎患者，这些关联没有什么不同。在有创通气下的危重患者中，肺补体激活似乎并不在 VILI 中起主要作用，甚至在肺损伤本身中也不起重要作用。