McCann U G, Schiller H J, Carney D E, Gatto L A, Steinberg J M, Nieman G F
Department of Surgery, State University of New York Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210. USA.
J Surg Res. 2001 Aug;99(2):335-42. doi: 10.1006/jsre.2001.6179.
Positive end-expiratory pressure (PEEP) reduces ventilator-induced lung injury (VILI), presumably by mechanically stabilizing alveoli and decreasing intrapulmonary shear. Although there is indirect support for this concept in the literature, direct evidence is lacking. In a surfactant depletion model of acute lung injury we observed unstable alveolar mechanics referred to as repeated alveolar collapse and expansion (RACE) as measured by changes in alveolar area from inspiration to expiration (I - E(Delta)). We tested the hypothesis that over a range of tidal volumes PEEP would prevent RACE by mechanically stabilizing alveoli.
Yorkshire pigs were randomized to three groups: control (n = 4), Tween (surfactant-deactivating detergent) (n = 4), and Tween + PEEP (7 cm H(2)O) (n = 4). Using in vivo video microscopy individual alveolar areas were measured with computer image analysis at end inspiration and expiration over consecutive increases in tidal volume (7, 10, 15, 20, and 30 cc/kg.) I - E(Delta) was calculated for each alveolus.
Surfactant deactivation significantly increased I - E(Delta) at every tidal volume compared to controls (P < 0.05). PEEP prevented this change, returning I - E(Delta) to control levels over a spectrum of tidal volumes.
RACE occurs in our surfactant deactivation model of acute lung injury. PEEP mechanically stabilizes alveoli and prevents RACE over a range of tidal volumes. This is the first study to visually document the existence of RACE and the mechanical stabilizing effects of PEEP at the alveolar level. The ability of PEEP to stabilize alveoli and reduce shear during mechanical ventilation has important implications for therapeutic strategies directed at VILI and acute respiratory distress syndrome.
呼气末正压（PEEP）可减轻呼吸机诱导的肺损伤（VILI），推测其机制是通过机械性稳定肺泡并降低肺内剪切力。尽管文献中有对此概念的间接支持，但缺乏直接证据。在急性肺损伤的表面活性剂耗竭模型中，我们观察到肺泡力学不稳定，即从吸气到呼气（I-E（Δ））时肺泡面积变化所测量的反复肺泡萎陷和扩张（RACE）。我们测试了这样一个假设，即在一定潮气量范围内，PEEP可通过机械性稳定肺泡来预防RACE。
将约克夏猪随机分为三组：对照组（n = 4）、吐温组（表面活性剂失活去污剂）（n = 4）和吐温+PEEP（7 cm H₂O）组（n = 4）。使用体内视频显微镜，随着潮气量（7、10、15、20和30 cc/kg）连续增加，在吸气末和呼气末通过计算机图像分析测量单个肺泡面积。计算每个肺泡的I-E（Δ）。
与对照组相比，表面活性剂失活在每个潮气量下均显著增加I-E（Δ）（P < 0.05）。PEEP可防止这种变化，使I-E（Δ）在一系列潮气量范围内恢复到对照水平。
在我们的急性肺损伤表面活性剂失活模型中发生了RACE。PEEP在一定潮气量范围内机械性稳定肺泡并预防RACE。这是第一项在视觉上记录RACE存在以及PEEP在肺泡水平的机械稳定作用的研究。PEEP在机械通气期间稳定肺泡并降低剪切力的能力对针对VILI和急性呼吸窘迫综合征的治疗策略具有重要意义。
