Spinelli Elena, Colussi Giulia, Dal Santo Gaia, Scotti Eleonora, Marongiu Ines, Garbelli Erica, Mazzucco Alessandra, Dondossola Daniele, Maia Raquel, Battistin Michele, Biancolilli Osvaldo, Rosso Lorenzo, Gatti Stefano, Mauri Tommaso
Department of Anesthesia, Critical Care and Emergency, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.
Front Physiol. 2021 Apr 9;12:663313. doi: 10.3389/fphys.2021.663313. eCollection 2021.
Reducing the respiratory rate during extracorporeal membrane oxygenation (ECMO) decreases the mechanical power, but it might induce alveolar de-recruitment. Dissecting de-recruitment due to lung edema vs. the fraction due to hypoventilation may be challenging in injured lungs. We characterized changes in lung physiology (primary endpoint: development of atelectasis) associated with progressive reduction of the respiratory rate in healthy animals on ECMO. Six female pigs underwent general anesthesia and volume control ventilation (Baseline: PEEP 5 cmHO, Vt 10 ml/kg, I:E = 1:2, FiO 0.5, rate 24 bpm). Veno-venous ECMO was started and respiratory rate was progressively reduced to 18, 12, and 6 breaths per minute (6-h steps), while all other settings remained unchanged. ECMO blood flow was kept constant while gas flow was increased to maintain stable PaCO. At Baseline (without ECMO) and toward the end of each step, data from quantitative CT scan, electrical impedance tomography, and gas exchange were collected. Increasing ECMO gas flow while lowering the respiratory rate was associated with an increase in the fraction of non-aerated tissue (i.e., atelectasis) and with a decrease of tidal ventilation reaching the gravitationally dependent lung regions ( = 0.009 and = 0.018). Intrapulmonary shunt increased ( < 0.001) and arterial PaO decreased ( < 0.001) at lower rates. The fraction of non-aerated lung was correlated with longer expiratory time spent at zero flow ( = 0.555, = 0.011). Progressive decrease of respiratory rate coupled with increasing CO removal in mechanically ventilated healthy pigs is associated with development of lung atelectasis, higher shunt, and poorer oxygenation.
在体外膜肺氧合（ECMO）期间降低呼吸频率可降低机械功率，但可能会导致肺泡去复张。区分因肺水肿导致的去复张与因通气不足导致的去复张比例，对于受损肺来说可能具有挑战性。我们对接受ECMO的健康动物在呼吸频率逐渐降低时肺生理变化（主要终点：肺不张的发生）进行了特征描述。六只雌性猪接受全身麻醉并采用容量控制通气（基线：呼气末正压5 cmH₂O，潮气量10 ml/kg，吸呼比 = 1:2，吸入氧分数0.5，频率24次/分钟）。开始进行静脉 - 静脉ECMO，呼吸频率逐渐降至每分钟18次、12次和6次（每6小时调整一次），而所有其他设置保持不变。在ECMO血流量保持恒定的同时增加气体流量以维持稳定的动脉血二氧化碳分压（PaCO₂）。在基线（无ECMO）时以及每个步骤结束时，收集定量CT扫描、电阻抗断层扫描和气体交换的数据。在降低呼吸频率的同时增加ECMO气体流量与非通气组织比例增加（即肺不张）以及到达重力依赖肺区的潮气量减少相关（P = 0.009和P = 0.018）。较低呼吸频率时肺内分流增加（P < 0.001）且动脉血氧分压（PaO₂）降低（P < 0.001）。非通气肺的比例与零流量下较长的呼气时间相关（r = 0.555，P = 0.011）。在机械通气的健康猪中，呼吸频率逐渐降低并伴有二氧化碳清除增加与肺不张的发生、更高的分流以及更差的氧合相关。
