Abstract：
In acute respiratory distress syndrome, the role of positive end-expiratory pressure (PEEP) to prevent ventilator-induced lung injury is controversial. Randomized trials comparing higher versus lower PEEP strategies failed to demonstrate a clinical benefit. This may depend on the inter-individually variable potential for lung recruitment (i.e. recruitability), which would warrant PEEP individualization to balance alveolar recruitment and the unavoidable baby lung overinflation produced by high pressure. Many techniques have been used to assess recruitability, including lung imaging, multiple pressure-volume curves and lung volume measurement. The Recruitment-to-Inflation ratio (R/I) has been recently proposed to bedside assess recruitability without additional equipment. R/I assessment is a simplified technique based on the multiple pressure-volume curve concept: it is measured by monitoring respiratory mechanics and exhaled tidal volume during a 10-cmH2 O one-breath derecruitment maneuver after a short high-PEEP test. R/I scales recruited volume to respiratory system compliance, and normalizes recruitment to a proxy of actual lung size. With modest R/I (<0.3-0.4), setting low PEEP (5-8 cmH2 O) may be advisable; with R/I>0.6-0.7, high PEEP (≥15 cmH2 O) can be considered, provided that airway and/or transpulmonary plateau pressure do not exceed safety limits. In case of intermediate R/I (≈0.5), a more granular assessment of recruitability may be needed. This could be accomplished with advanced monitoring tools, like sequential lung volume measurement with granular R/I assessment or electrical impedance tomography monitoring during a decremental PEEP trial. In this review, we discuss R/I rationale, applications and limits, providing insights on its clinical use for PEEP selection in moderate-to-severe acute respiratory distress syndrome.
摘要：
在急性呼吸窘迫综合征中，呼气末正压(PEEP)预防呼吸机相关性肺损伤的作用存在争议.比较较高和较低PEEP策略的随机试验未能证明临床益处。这可能取决于肺募集的个体间可变潜力（即招募性），这将保证PEEP个性化，以平衡肺泡募集和高压产生的不可避免的婴儿肺过度膨胀。许多技术已经被用来评估招聘能力，包括肺部成像,多个压力-容积曲线和肺容积测量。最近提出了招聘与通货膨胀比率（R/I），用于在没有额外设备的情况下评估招聘能力。R/I评估是一种基于多重压力-容积曲线概念的简化技术：它是通过在10-cmH2 O一次呼吸解除操作后监测呼吸力学和呼出潮气量来测量的。短暂的高PEEP测试。R/I量表招募体积对呼吸系统的依从性，并将招募标准化为实际肺大小的代表。在适度的R/I（<0.3-0.4）的情况下，建议设置低PEEP（5-8cmH2 O）；如果R/I>0.6-0.7，则可以考虑高PEEP（≥15cmH2 O），前提是气道和/或经肺平台压力不超过安全限值。在中间R/I(≈0.5)的情况下，可能需要对招聘性进行更细致的评估。这可以用先进的监测工具来完成，例如，在PEEP递减试验期间，采用颗粒R/I评估或电阻抗断层扫描监测的序贯肺容积测量。在这次审查中,我们讨论R/I的基本原理，应用和限制，提供其在中度至重度急性呼吸窘迫综合征中选择PEEP的临床用途的见解。
