Cardiopulmonary resuscitation (CPR) decreases lung volume below the functional residual capacity and can generate intrathoracic airway closure. Conversely, large insufflations can induce thoracic distension and jeopardize circulation. The capnogram (CO2 signal) obtained during continuous chest compressions can reflect intrathoracic airway closure, and we hypothesized here that it can also indicate thoracic distension. To test whether a specific capnogram may identify thoracic distension during CPR and to assess the impact of thoracic distension on gas exchange and hemodynamics. (1) In out-of-hospital cardiac arrest patients, we identified on capnograms three patterns: intrathoracic airway closure, thoracic distension or regular pattern. An algorithm was designed to identify them automatically. (2) To link CO2 patterns with ventilation, we conducted three experiments: (i) reproducing the CO2 patterns in human cadavers, (ii) assessing the influence of tidal volume and respiratory mechanics on thoracic distension using a mechanical lung model and (iii) exploring the impact of thoracic distension patterns on different circulation parameters during CPR on a pig model. (1) Clinical data: 202 capnograms were collected. Intrathoracic airway closure was present in 35%, thoracic distension in 22% and regular pattern in 43%. (2) Experiments: (i) Higher insufflated volumes reproduced thoracic distension CO2 patterns in 5 cadavers. (ii) In the mechanical lung model, thoracic distension patterns were associated with higher volumes and longer time constants. (iii) In six pigs during CPR with various tidal volumes, a CO2 pattern of thoracic distension, but not tidal volume per se, was associated with a significant decrease in blood pressure and cerebral perfusion. During CPR, capnograms reflecting intrathoracic airway closure, thoracic distension or regular pattern can be identified. In the animal experiment, a thoracic distension pattern on the capnogram is associated with a negative impact of ventilation on blood pressure and cerebral perfusion during CPR, not predicted by tidal volume per se.

中文翻译：

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一种新的二氧化碳图分析来指导心肺复苏期间的通气：临床和实验观察

心肺复苏术 (CPR) 将肺容量减少到功能残气量以下，并可能导致胸腔内气道关闭。相反，大量吹气会导致胸廓扩张并危及血液循环。在连续胸外按压期间获得的二氧化碳图（CO2 信号）可以反映胸腔内气道关闭情况，我们在这里假设它也可以指示胸廓扩张。测试特定的二氧化碳图是否可以识别 CPR 期间的胸廓扩张，并评估胸廓扩张对气体交换和血流动力学的影响。(1) 在院外心脏骤停患者中，我们在二氧化碳图上确定了三种模式：胸内气道关闭、胸廓扩张或规则模式。设计了一种算法来自动识别它们。(2) 将 CO2 模式与通风联系起来，我们进行了三个实验：(i) 在人类尸体中重现 CO2 模式，(ii) 使用机械肺模型评估潮气量和呼吸力学对胸廓扩张的影响，以及 (iii) 探索胸廓扩张模式对不同循环的影响猪模型心肺复苏期间的参数。(1) 临床数据：收集了 202 张二氧化碳图。35% 存在胸内气道关闭，22% 存在胸廓扩张，43% 存在规则模式。(2) 实验： (i) 较高的吹气体积再现了 5 具尸体的胸胀 CO2 模式。(ii) 在机械肺模型中，胸廓扩张模式与更高的体积和更长的时间常数相关。(iii) 在六头不同潮气量的 CPR 猪中，CO2 模式的胸廓扩张，但不是潮气量本身，与血压和脑灌注显着降低有关。在 CPR 期间，可以识别反映胸腔内气道关闭、胸廓扩张或规则模式的二氧化碳图。在动物实验中，二氧化碳图上的胸廓扩张模式与 CPR 期间通气对血压和脑灌注的负面影响有关，潮气量本身无法预测。