Mechanical ventilation is a life-saving therapy in patients with acute respiratory distress syndrome (ARDS). However, mechanical ventilation itself causes severe co-morbidities in that it can trigger ventilator-associated lung injury (VALI) in humans or ventilator-induced lung injury (VILI) in experimental animal models. Therefore, optimization of ventilation strategies is paramount for the effective therapy of critical care patients. A major problem in the stratification of critical care patients for personalized ventilation settings, but even more so for our overall understanding of VILI, lies in our limited insight into the effects of mechanical ventilation at the actual site of injury, i.e., the alveolar unit. Unfortunately, global lung mechanics provide for a poor surrogate of alveolar dynamics and methods for the in-depth analysis of alveolar dynamics on the level of individual alveoli are sparse and afflicted by important limitations. With alveolar dynamics in the intact lung remaining largely a “black box,” our insight into the mechanisms of VALI and VILI and the effectiveness of optimized ventilation strategies is confined to indirect parameters and endpoints of lung injury and mortality. In the present review, we discuss emerging concepts of alveolar dynamics including alveolar expansion/contraction, stability/instability, and opening/collapse. Many of these concepts remain still controversial, in part due to limitations of the different methodologies applied. We therefore preface our review with an overview of existing technologies and approaches for the analysis of alveolar dynamics, highlighting their individual strengths and limitations which may provide for a better appreciation of the sometimes diverging findings and interpretations. Joint efforts combining key technologies in identical models to overcome the limitations inherent to individual methodologies are needed not only to provide conclusive insights into lung physiology and alveolar dynamics, but ultimately to guide critical care patient therapy.

中文翻译：

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健康和受伤肺机械通气期间的肺泡动力学

机械通气是急性呼吸窘迫综合征（ARDS）患者的一种挽救生命的疗法。然而，机械通气本身会引起严重的并发症，因为它可能引发人类呼吸机相关性肺损伤（VALI）或实验动物模型中的呼吸机相关性肺损伤（VILI）。因此，优化通气策略对于重症患者的有效治疗至关重要。对重症监护患者进行个性化通气设置分层的一个主要问题，更重要的是我们对 VILI 的整体理解，在于我们对机械通气对实际损伤部位（即肺泡单位）的影响的了解有限。不幸的是，整体肺力学提供的肺泡动力学的替代品很差，并且在个体肺泡水平上深入分析肺泡动力学的方法很少并且受到重要的限制。由于完整肺中的肺泡动力学在很大程度上仍然是一个“黑匣子”，我们对 VALI 和 VILI 机制以及优化通气策略有效性的了解仅限于肺损伤和死亡率的间接参数和终点。在本综述中，我们讨论了肺泡动力学的新兴概念，包括肺泡扩张/收缩、稳定性/不稳定和开放/塌陷。其中许多概念仍然存在争议，部分原因是所应用的不同方法的局限性。因此，我们在回顾之前概述了用于分析肺泡动力学的现有技术和方法，强调了它们各自的优势和局限性，这可能有助于更好地理解有时存在分歧的发现和解释。需要共同努力，将相同模型中的关键技术结合起来，克服各个方法固有的局限性，不仅可以提供对肺生理学和肺泡动力学的结论性见解，而且最终可以指导重症监护患者的治疗。