Zucker A R, Holm B A, Crawford G P, Ridge K, Wood L D, Sznajder J I
Section of Pediatric Critical Care, Wyler Children's Hospital, Chicago, Illinois.
J Appl Physiol (1985). 1992 Aug;73(2):679-86. doi: 10.1152/jappl.1992.73.2.679.
Alveolar edema inactivates surfactant, and surfactant depletion causes edema by reducing lung interstitial pressure (Pis). We reasoned that surfactant repletion might reduce edema by raising Pis after acute lung injury and that positive end-expiratory pressure (PEEP) might facilitate this effect. One hour after tracheal administration of hydrochloric acid in 18 anesthetized dogs with transmural pulmonary capillary wedge pressure of 8 Torr, the animals were randomized into three groups: in the SURF + PEEP group, 50 mg/kg of calf lung surfactant extract (CLSE) was instilled into each main stem bronchus with 8 cmH2O of PEEP; in the SAL + PEEP group, PEEP was followed by an equal volume of saline (SAL); in the SURF group, CLSE was given without PEEP. After 5 h, edema in excised lungs (wet-to-dry weight ratios) was significantly less in the SURF + PEEP group (9.1 +/- 1.0) than in the other groups (11.3 +/- 1.8 and 11.3 +/- 1.8, respectively). In the SURF + PEEP group, pulmonary venous admixture fell by 6%; this change was different from the 7% increase in the SAL + PEEP group and 40% increase in the SURF group (P less than 0.05). Airway secretions obtained in the SURF + PEEP group had normal minimum surface tensions of 4 +/- 2 mN/m, a value much lower than in SAL + PEEP and SURF groups (32 +/- 4 and 22 +/- 7 mN/m, respectively). We conclude that surfactant normalizes surface tension and decreases transcapillary hydrostatic forces in this lung injury model, thereby reducing edema formation and improving gas exchange. These benefits occur only if surfactant is given with PEEP, allowing surfactant access to the alveoli and/or minimizing its inhibition by edema proteins.
肺泡水肿会使表面活性物质失活，而表面活性物质耗竭会通过降低肺间质压力（Pis）导致水肿。我们推测，在急性肺损伤后，补充表面活性物质可能通过提高Pis来减轻水肿，而呼气末正压（PEEP）可能会促进这种作用。在18只经气管给予盐酸、跨壁肺毛细血管楔压为8托的麻醉犬中，给药1小时后，将动物随机分为三组：在SURF + PEEP组中，将50 mg/kg的小牛肺表面活性物质提取物（CLSE）滴入每个主支气管，并给予8 cmH2O的PEEP；在SAL + PEEP组中，在给予PEEP后给予等量的生理盐水（SAL）；在SURF组中，给予CLSE但不给予PEEP。5小时后，SURF + PEEP组切除肺的水肿（湿重与干重之比）明显低于其他组（分别为9.1±1.0，而其他组为11.3±1.8和11.3±1.8）。在SURF + PEEP组中，肺静脉混合血减少了6%；这种变化与SAL + PEEP组增加7%和SURF组增加40%不同（P<0.05）。SURF + PEEP组获得的气道分泌物的正常最小表面张力为4±2 mN/m，该值远低于SAL + PEEP组和SURF组（分别为32±4和22±7 mN/m）。我们得出结论，在该肺损伤模型中，表面活性物质使表面张力正常化并降低跨毛细血管静水压，从而减少水肿形成并改善气体交换。只有在给予PEEP的情况下给予表面活性物质，这些益处才会出现，这使得表面活性物质能够进入肺泡和/或最小化其被水肿蛋白的抑制作用。
