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Response to letter by Drs. Bottinger and van der Hoorn
Intensive Care Medicine Experimental Pub Date : 2019-06-06 , DOI: 10.1186/s40635-019-0258-x
David A Berlin 1 , Seth Manoach 1 , Paul M Heerdt 2
Affiliation  

* Correspondence: paul.heerdt@yale.edu Division of Applied Hemodnamics, Yale University School of Medicine, New Haven, USA Full list of author information is available at the end of the article We thank Drs. Bottinger and van der Hoorn for their close reading of our manuscript and their comments. As they point out, our study was designed to primarily evaluate how the relatively unique capability of expiratory ventilatory assistance (EVA) to generate negative end-expiratory pressure (NEEP) affected blood pressure and cardiac output flow in the setting of profound hemorrhage. For the study, after removing 40 mL/kg of blood to induce marked hypotension, subjects received either conventional positive pressure ventilation with 0 end-expiratory pressure or EVA ventilation with NEEP. Minute ventilation was matched for both groups and under these conditions, arterial CO2 was higher in the group receiving EVA ventilation. This difference needs to be interpreted in the context of two very important considerations. First, the study was designed to assess potential hemodynamic benefits of EVA with NEEP not necessarily optimize ventilation. With NEEP of − 8 cmH2O, EVA required a peak inspiratory pressure of only ~ 6–7 cmH20 to produce a tidal volume and PaO2 similar to that generated by conventional ventilation with 0 end-expiratory pressure and a peak inspiratory pressure of 20 cmH20. The ability to ventilate with this low PIP is remarkable and clearly contributed to the observed hemodynamic benefit. It also suggests that during hemorrhagic shock, increased gas flow and higher PIP can be used at least intermittently in conjunction with NEEP without major loss of hemodynamic benefit. Ultimately, we agree with Drs. Bottinger and van der Hoorn that broad interpretation of our results in terms of CO2 removal is not warranted given the specific use of EVA with NEEP and conditions of our experimental protocol. We also agree that the experimental model is not indicative of the established clinical use of EVA rescue ventilation with an obstructed airway and that choice of the catheter and mode of ventilation could have affected the observed efficiency of gas exchange. Second, study results indicate that the improvements in blood pressure and flow, in conjunction with maintenance of oxygenation, during EVA with NEEP outweigh any decrement in CO2 elimination with a fixed minute ventilation. In the absence of fluid administration or other resuscitative measures, 1 h after marked hemorrhage mean arterial pressure was double that in subjects with conventional ventilation and cardiac output nearly 60% higher. This relatively profound response may have particular short-term benefit in a clinical setting where it is highly likely that volume resuscitation will be implemented sooner and ventilation can be adjusted based upon blood gas analysis.

中文翻译:

回复 Drs 的来信 博廷格和范德霍恩

* 通讯作者:paul.heerdt@yale.edu 美国纽黑文耶鲁大学医学院应用血液动力学部作者信息的完整列表在文章末尾提供我们感谢 Drs。Bottinger 和 van der Hoorn 仔细阅读了我们的手稿和他们的评论。正如他们指出的那样,我们的研究旨在主要评估呼气辅助通气 (EVA) 产生负呼气末压 (NEEP) 的相对独特的能力如何在严重出血的情况下影响血压和心输出量。在这项研究中,在抽取 40 mL/kg 的血液以诱发明显的低血压后,受试者接受了 0 呼气末压力的常规正压通气或 NEEP 的 EVA 通气。两组的分钟通气量相匹配,在这些条件下,接受 EVA 通气组的动脉 CO2 较高。需要在两个非常重要的考虑因素的背景下解释这种差异。首先,该研究旨在评估 EVA 与 NEEP 的潜在血流动力学益处,但不一定优化通气。在 NEEP 为 − 8 cmH2O 的情况下,EVA 只需要约 6–7 cmH2O 的峰值吸气压力即可产生潮气量和 PaO2,这与传统通气产生的潮气量和 PaO2 相似,呼气末压力为 0,吸气峰值压力为 20 cmH2O。这种低 PIP 的通气能力是显着的,并且明显有助于观察到的血流动力学益处。它还表明,在失血性休克期间,增加的气流和更高的 PIP 至少可以间歇性地与 NEEP 结合使用,而不会严重损失血液动力学益处。最终,我们同意 Drs. Bottinger 和 van der Hoorn 认为,鉴于 EVA 与 NEEP 的具体使用以及我们实验协议的条件,我们在 CO2 去除方面的结果的广泛解释是不合理的。我们也同意,实验模型并不表明 EVA 救援通气在气道阻塞的临床应用中的确立,导管和通气模式的选择可能会影响观察到的气体交换效率。其次,研究结果表明,在 EVA 和 NEEP 期间,血压和流量的改善以及氧合的维持,超过了固定分钟通气量时 CO2 消除的任何减少。在没有输液或其他复苏措施的情况下,明显出血后 1 小时的平均动脉压是常规通气和心输出量高出近 60% 的受试者的两倍。这种相对深刻的反应可能在临床环境中具有特别的短期益处,因为很可能会更快实施容量复苏,并且可以根据血气分析调整通气。
更新日期:2019-06-06
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