Laboratory of Pulmonary Investigation, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Crit Care Med. 2010 Nov;38(11):2207-14. doi: 10.1097/CCM.0b013e3181f3e076.
In acute lung injury, recruitment maneuvers have been used to open collapsed lungs and set positive end-expiratory pressure, but their effectiveness may depend on the degree of lung injury. This study uses a single experimental model with different degrees of lung injury and tests the hypothesis that recruitment maneuvers may have beneficial or deleterious effects depending on the severity of acute lung injury. We speculated that recruitment maneuvers may worsen lung mechanical stress in the presence of alveolar edema.
Prospective, randomized, controlled experimental study.
University research laboratory.
Thirty-six Wistar rats randomly divided into three groups (n = 12 per group).
In the control group, saline was intraperitoneally injected, whereas moderate and severe acute lung injury animals received paraquat intraperitoneally (20 mg/kg [moderate acute lung injury] and 25 mg/kg [severe acute lung injury]). After 24 hrs, animals were further randomized into subgroups (n = 6/each) to be recruited (recruitment maneuvers: 40 cm H₂O continuous positive airway pressure for 40 secs) or not, followed by 1 hr of protective mechanical ventilation (tidal volume, 6 mL/kg; positive end-expiratory pressure, 5 cm H₂O).
Only severe acute lung injury caused alveolar edema. The amounts of alveolar collapse were similar in the acute lung injury groups. Static lung elastance, viscoelastic pressure, hyperinflation, lung, liver, and kidney cell apoptosis, and type 3 procollagen and interleukin-6 mRNA expressions in lung tissue were more elevated in severe acute lung injury than in moderate acute lung injury. After recruitment maneuvers, static lung elastance, viscoelastic pressure, and alveolar collapse were lower in moderate acute lung injury than in severe acute lung injury. Recruitment maneuvers reduced interleukin-6 expression with a minor detachment of the alveolar capillary membrane in moderate acute lung injury. In severe acute lung injury, recruitment maneuvers were associated with hyperinflation, increased apoptosis of lung and kidney, expression of type 3 procollagen, and worsened alveolar capillary injury.
In the presence of alveolar edema, regional mechanical heterogeneities, and hyperinflation, recruitment maneuvers promoted a modest but consistent increase in inflammatory and fibrogenic response, which may have worsened lung function and potentiated alveolar and renal epithelial injury.
在急性肺损伤中，采用复张手法来开放塌陷的肺并设置呼气末正压，但这些方法的效果可能取决于肺损伤的程度。本研究使用一个具有不同程度肺损伤的单一实验模型，并检验了以下假说，即复张手法可能会根据急性肺损伤的严重程度产生有益或有害的影响。我们推测，在存在肺泡水肿的情况下，复张手法可能会加重肺的机械性应激。
前瞻性、随机、对照的实验研究。
大学研究实验室。
36 只 Wistar 大鼠，随机分为 3 组（每组 12 只）。
在对照组中，大鼠腹腔内注射生理盐水，而中度和重度急性肺损伤动物腹腔内注射百草枯（20 mg/kg [中度急性肺损伤]和 25 mg/kg [重度急性肺损伤]）。24 小时后，动物进一步随机分为亚组（每组 6 只）进行复张（复张手法：40 cm H₂O 持续气道正压 40 秒）或不进行复张，然后进行 1 小时的保护性机械通气（潮气量 6 mL/kg，呼气末正压 5 cm H₂O）。
只有重度急性肺损伤才会导致肺泡水肿。急性肺损伤组的肺泡塌陷量相似。重度急性肺损伤的静态肺弹性、粘弹压力、过度充气、肺、肝、肾细胞凋亡以及肺组织中Ⅲ型前胶原和白细胞介素-6mRNA 的表达均高于中度急性肺损伤。复张手法后，中度急性肺损伤的静态肺弹性、粘弹压力和肺泡塌陷量均低于重度急性肺损伤。复张手法降低了中度急性肺损伤的白细胞介素-6 表达，并使肺泡毛细血管膜轻微分离。在重度急性肺损伤中，复张手法与过度充气、肺和肾上皮细胞凋亡增加、Ⅲ型前胶原表达以及肺泡毛细血管损伤加重有关。
在存在肺泡水肿、区域性机械不均一性和过度充气的情况下，复张手法会导致炎症和纤维化反应适度但持续增加，这可能会使肺功能恶化，并加重肺泡和肾上皮损伤。
