In refractory out-of-hospital cardiac arrest, the patient is commonly transported to hospital with mechanical continuous chest compressions (CCC). Limited data are available on the optimal ventilation strategy. Accordingly, we compared arterial oxygenation and haemodynamics during manual asynchronous continuous ventilation and compressions with a 30:2 compression-to-ventilation ratio together with the use of 10 cmH2O positive end-expiratory pressure (PEEP). Intubated and anaesthetized landrace pigs with electrically induced ventricular fibrillation were left untreated for 5 min (n = 31, weight ca. 55 kg), after which they were randomized to either the CCC group or the 30:2 group with the the LUCAS® 2 piston device and bag-valve ventilation with 100% oxygen targeting a tidal volume of 8 ml/kg with a PEEP of 10 cmH2O for 35 min. Arterial blood samples were analysed every 5 min, vital signs, near-infrared spectroscopy and electrical impedance tomography (EIT) were measured continuously, and post-mortem CT scans of the lungs were obtained. The arterial blood values (median + interquartile range) at the 30-min time point were as follows: PaO2: 180 (86–302) mmHg for the 30:2 group; 70 (49–358) mmHg for the CCC group; PaCO2: 41 (29–53) mmHg for the 30:2 group; 44 (21–67) mmHg for the CCC group; and lactate: 12.8 (10.4–15.5) mmol/l for the 30:2 group; 14.7 (11.8–16.1) mmol/l for the CCC group. The differences were not statistically significant. In linear mixed models, there were no significant differences between the groups. The mean arterial pressures from the femoral artery, end-tidal CO2, distributions of ventilation from EIT and mean aeration of lung tissue in post-mortem CTs were similar between the groups. Eight pneumothoraces occurred in the CCC group and 2 in the 30:2 group, a statistically significant difference (p = 0.04). The 30:2 and CCC protocols with a PEEP of 10 cmH2O resulted in similar gas exchange and vital sign outcomes in an experimental model of prolonged cardiac arrest with mechanical compressions, but the CCC protocol resulted in more post-mortem pneumothoraces.

中文翻译：

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长时间实验性心肺复苏期间的氧合和通气，采用连续或 30:2 压缩通气比以及 10 cmH20 呼气末正压

对于难治性院外心脏骤停，患者通常会被送往医院进行机械连续胸外按压 (CCC)。关于最佳通气策略的可用数据有限。因此，我们比较了手动异步连续通气和按压（压缩通气比为 30:2）以及使用 10 cmH2O 呼气末正压 (PEEP) 期间的动脉氧合和血流动力学。患有电诱发心室颤动的插管和麻醉的地方猪未经治疗 5 分钟（n = 31，体重约 55 kg），之后将它们随机分为 CCC 组或使用 LUCAS® 2 的 30:2 组活塞装置和袋阀通气，100% 氧气，潮气量为 8 ml/kg，PEEP 为 10 cmH2O，持续 35 分钟。每 5 分钟分析一次动脉血样本，连续测量生命体征、近红外光谱和电阻抗断层扫描 (EIT)，并获得死后肺部 CT 扫描。 30 分钟时间点的动脉血值（中位值 + 四分位数范围）如下： PaO2：30:2 组为 180 (86–302) mmHg； CCC 组为 70 (49–358) mmHg； PaCO2：30:2 组为 41 (29–53) mmHg； CCC 组为 44 (21–67) mmHg；乳酸：30:2 组为 12.8 (10.4–15.5) mmol/l； CCC 组为 14.7 (11.8–16.1) mmol/l。差异无统计学意义。在线性混合模型中，各组之间没有显着差异。股动脉的平均动脉压、呼气末二氧化碳、EIT 的通气分布以及死后 CT 中肺组织的平均通气量在各组之间相似。 CCC 组发生 8 例气胸，30:2 组发生 2 例气胸，差异有统计学意义（p = 0.04）。在机械压缩长时间心脏骤停的实验模型中，PEEP 为 10 cmH2O 的 30:2 和 CCC 方案产生相似的气体交换和生命体征结果，但 CCC 方案导致更多的死后气胸。