D'Albo Rosanna, Pozzi Tommaso, Nicolardi Rosmery V, Galizia Mauro, Catozzi Giulia, Ghidoni Valentina, Donati Beatrice, Romitti Federica, Herrmann Peter, Busana Mattia, Gattarello Simone, Collino Francesca, Sonzogni Aurelio, Camporota Luigi, Marini John J, Moerer Onnen, Meissner Konrad, Gattinoni Luciano
Department of Anesthesiology, University Medical Center Göttingen, Göttingen, Germany.
Department of Medical and Surgical Sciences, Alma Mater Studiorum, University of Bologna, Bologna, Italy.
Intensive Care Med Exp. 2024 Jul 30;12(1):65. doi: 10.1186/s40635-024-00649-0.
Mechanical power (MP) is a summary variable incorporating all causes of ventilator-induced-lung-injury (VILI). We expressed MP as the ratio between observed and normal expected values (MP).
To define a threshold value of MP leading to the development of VILI.
In a population of 82 healthy pigs, a threshold of MP for VILI, as assessed by histological variables and confirmed by using unsupervised cluster analysis was 4.5. The population was divided into two groups with MP above or below the threshold.
We measured physiological variables every six hours. At the end of the experiment, we measured lung weight and wet-to-dry ratio to quantify edema. Histological samples were analyzed for alveolar ruptures, inflammation, alveolar edema, atelectasis. An MP threshold of 4.5 was associated with worse injury, lung weight, wet-to-dry ratio and fluid balance (all p < 0.001). After 48 h, in the two MP clusters (above or below 4.5), respiratory system elastance, mean pulmonary artery pressure and physiological dead space differed by 32%, 36% and 22%, respectively (all p < 0.001), being worse in the high MP group. Also, the changes in driving pressure, lung elastance, pulmonary artery occlusion pressure, central venous pressure differed by 17%, 64%, 8%, 25%, respectively (all p < 0.001).
The main limitation of this study is its retrospective design. In addition, the computation for the expected MP in pigs is based on arbitrary criteria. Different values of expected MP may change the absolute value of MP ratio but will not change the concept of the existence of an injury threshold.
The concept of MP is a physiological and intuitive way to quantify the risk of ventilator-induced lung injury. Our results suggest that a mechanical power ratio > 4.5 MP in healthy lungs subjected to 48 h of mechanical ventilation appears to be a threshold for the development of ventilator-induced lung injury, as indicated by the convergence of histological, physiological, and anatomical alterations. In humans and in lungs that are already injured, this threshold is likely to be different.
机械功率（MP）是一个综合变量，包含了呼吸机诱发肺损伤（VILI）的所有原因。我们将MP表示为观察值与正常预期值之比（MP）。
确定导致VILI发生的MP阈值。
在82头健康猪的群体中，通过组织学变量评估并经无监督聚类分析证实的VILI的MP阈值为4.5。将该群体分为MP高于或低于阈值的两组。
我们每6小时测量一次生理变量。在实验结束时，我们测量肺重量和湿干比以量化水肿。对组织学样本进行肺泡破裂、炎症、肺泡水肿、肺不张分析。MP阈值为4.5与更严重的损伤、肺重量、湿干比和液体平衡相关（所有p<0.001）。48小时后，在两个MP聚类（高于或低于4.5）中，呼吸系统弹性、平均肺动脉压和生理死腔分别相差32%、36%和22%（所有p<0.001），在高MP组中更差。此外，驱动压力、肺弹性、肺动脉闭塞压、中心静脉压的变化分别相差17%、64%、8%、25%（所有p<0.001）。
本研究的主要局限性是其回顾性设计。此外，猪预期MP的计算基于任意标准。预期MP的不同值可能会改变MP比值的绝对值，但不会改变损伤阈值存在这一概念。
MP的概念是量化呼吸机诱发肺损伤风险的一种生理且直观的方法。我们的结果表明，在接受48小时机械通气的健康肺中，机械功率比>4.5 MP似乎是呼吸机诱发肺损伤发生的阈值，组织学、生理学和解剖学改变的趋同表明了这一点。在人类和已经受损的肺中，这个阈值可能会有所不同。
