Department of Critical Care Medicine, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada.
Department of Anesthesia, Critical Care and Emergency, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
Am J Respir Crit Care Med. 2022 Jun 1;205(11):1311-1319. doi: 10.1164/rccm.202111-2483OC.
The inspiratory rise in transpulmonary pressure during mechanical ventilation increases right ventricular (RV) afterload. One mechanism is that when Palv exceeds left atrial pressure, West zone 1 or 2 (non-zone 3) conditions develop, and Palv becomes the downstream pressure opposing RV ejection. The Vt at which this impact on the right ventricle becomes hemodynamically evident is not well established. To determine the magnitude of RV afterload and prevalence of significant non-zone 3 conditions during inspiration across the range of Vt currently prescribed in clinical practice. In postoperative passively ventilated cardiac surgery patients, we measured right atrial, right ventricle, pulmonary artery, pulmonary artery occlusion pressure, plateau pressure, and esophageal pressure during short periods of controlled ventilation, with Vt increments ranging between 2 and 12 ml/kg predicted body weight (PBW). The inspiratory increase in RV afterload was evaluated hemodynamically and echocardiographically. The prevalence of non-zone 3 conditions was determined using two definitions based on changes in esophageal pressure, pulmonary artery occlusion pressure, and plateau pressure. Fifty-one patients were studied. There was a linear relationship between Vt, driving pressure, transpulmonary pressure, and the inspiratory increase in the RV isovolumetric contraction pressure. Echocardiographically, increasing Vt was associated with a greater inspiratory increase in markers of afterload and a decrease in stroke volume. Non-zone 3 conditions were present in >50% of subjects at a Vt ⩾ 6 ml/kg PBW. In the Vt range currently prescribed, RV afterload increases with increasing Vt. A mechanical ventilation strategy that limits Vt and driving pressure is cardioprotective.
在机械通气过程中，跨肺压的吸气上升会增加右心室（RV）后负荷。一种机制是，当 Palv 超过左心房压力时，West zone 1 或 2（非 zone 3）条件会发展，并且 Palv 成为对抗 RV 射血的下游压力。对右心室产生这种影响的 Vt 尚未得到很好的确定。为了确定在目前临床实践中规定的 Vt 范围内，RV 后负荷的大小以及在吸气过程中出现显著非 zone 3 条件的频率。在被动通气的心脏手术后患者中，我们在短时间内测量了右心房、右心室、肺动脉、肺动脉闭塞压、平台压和食管压，在控制通气期间，Vt 增量在 2 至 12 ml/kg 预测体重（PBW）之间。通过血流动力学和超声心动图评估 RV 后负荷的吸气增加。使用基于食管压、肺动脉闭塞压和平台压变化的两种定义来确定非 zone 3 条件的患病率。研究了 51 名患者。Vt、驱动压、跨肺压和 RV 等容收缩压的吸气增加之间存在线性关系。超声心动图显示，随着 Vt 的增加，后负荷的吸气增加标志物和每搏量增加。在 Vt ⩾ 6 ml/kg PBW 时，超过 50%的受试者存在非 zone 3 条件。在目前规定的 Vt 范围内，RV 后负荷随 Vt 的增加而增加。限制 Vt 和驱动压的机械通气策略具有心脏保护作用。
