Effects of the OLC following ARDSnet ventilation in patients with early ARDS

Background: Ventilation with low tidal volume (VT) is well recognized as a protective approach to patients with acute respiratory distress syndrome (ARDS), but the optimal level of positive end-expiratory pressure (PEEP) remains uncertain. This study aims to evaluate two protective ventilatory strategies sequentially applied in patients with early ARDS. Methods: In this prospective cohort study, fifteen patients were ventilated during 24h with positive end-expiratory pressure (PEEP) adjusted according to the ARDSnet low-PEEP table (ARDSnet-24h). During the next 24h, nine patients with PaO2/FIO2 ratio below 350 mmHg were ventilated with PEEP titrated according to the Open Lung Concept protocol (ARDSnet+OLC). In the other six patients, regardless of their PaO2/FIO2 ratio, the ARDSnet remained for a further 24 h (ARDSnet-48h). Ventilatory variables, arterial bloodgas and cytokine were obtained at baseline, 24 and 48h. Additionally, whole-lungcomputed tomography was acquired at 24 and 48h. Results: A sustained improvement in PaO2/FIO2 ratio (P=0.008) with a decrease in collapsed regions (P=0.008) was observed in the ARDSnet+OLC group compared with the ARDSnet-24h group. A reduction in IL-6 in plasma (P<0.02) was observed throughout the protocol in the ARDSnet+OLC group. Compared with the ARDSnet-48h group, the ARDSnet+OLC presented smaller amounts of collapsed areas (P=0.018) without significant differences in hyperinflated regions and in driving and plateau pressures. Conclusions: In this set of patients with early ARDS, mechanical ventilation with an individually tailored PEEP sustained improved pulmonary function with better aeration, without significant increase in hyperinflated areas”

背景：小潮气量（low tidal volume, VT）通气已被公认为急性呼吸窘迫综合征（acute respiratory distress syndrome, ARDS）患者的保护性通气策略，但呼气末正压（positive end-expiratory pressure, PEEP）的最优水平仍不明确。本研究旨在评估两种保护性通气策略在早期ARDS患者中的序贯应用效果。
方法：本前瞻性队列研究中，15例患者在最初24小时采用基于ARDSnet低PEEP表格调整PEEP的通气方案（记为ARDSnet-24h组）。在随后的24小时内，9例动脉血氧分压/吸入氧分数（PaO2/FIO2）低于350 mmHg的患者采用基于开放肺概念（Open Lung Concept, OLC）方案滴定PEEP的通气策略（记为ARDSnet+OLC组）。其余6例患者无论其PaO2/FIO2水平如何，均继续采用ARDSnet方案通气24小时（记为ARDSnet-48h组）。分别于基线、24小时及48小时采集通气参数、动脉血气及细胞因子样本。此外，于24小时及48小时行全肺计算机断层扫描（computed tomography, CT）检查。
结果：与ARDSnet-24h组相比，ARDSnet+OLC组患者的PaO2/FIO2比值持续改善（P=0.008），同时肺萎陷区域减少（P=0.008）。ARDSnet+OLC组患者的血浆白细胞介素6（IL-6）水平在整个研究方案中均呈下降趋势（P<0.02）。与ARDSnet-48h组相比，ARDSnet+OLC组的肺萎陷区域体积更小（P=0.018），而过度充气区域、驱动压及平台压均无显著差异。
结论：在本研究纳入的早期ARDS患者中，采用个体化滴定PEEP的机械通气策略可持续改善肺功能，优化肺通气状态，且未显著增加过度充气区域的体积。