双相正压通气对急性肺损伤猪肺复张／开放的影响

Effects of APRV-BIPAP ventilation on lung recruitment/open maneuvers in piglets with acute lung injury

目的探讨气道压力释放-双相气道正压通气（APRV—BIPAP）模式下，逐步递增压力组合水平肺复张／开放策略（lung recruitment／open maneuvers，RMs）的疗效，摸索最佳压力组合，观察对血流动力学等影响。方法经腹腔注射大肠杆菌制作猪急性肺损伤（acute lung injury，Au）模型，APRV-BI—PAP下，逐步递增压力组合（Phigh／How），即RM1（30／15）、RM2（35／20）、RM3（40／25）、RM4（45／30）、RM5（50／35）、RM6（55／40）、RM7（60／45）cmH2O实施RMs，监测氧合指数（PaO2／FiO2）、血流动力学指标、平均气道压（Pmean）变化，吸气相CT扫描，评价RMs疗效。RMs完成后，处死取肺组织行病理学检查。所有资料应用SPSS11．5统计软件包对数据进行统计学分析，采用自身前后对照，各种测定值以均数±标准差（x±s）表示，多组间采用随机区组办差分析，PaO2／FiO2与肺组织萎陷程度相关性比较采用Pearson相关分析，P〈0．05为差异具有统计学意义。结果健康幼猪8头，成模后CT扫描均显示不同程度肺泡萎陷。随RMs，PaO2／FiO2改善，肺泡萎陷减少，以RM2后改善最明显（P〈0．05），但非病变区域有肺泡过度膨胀；随压力递增，心率（HR）增快（P〈0．05），平均动脉压（MAP）下降（P〈0．05），PIP、Pmean和中心静脉压（CVP）升高（P〈0．05），但RMs完成后能恢复到RMs前水平（P〉0.05）；研究过程中未发生气胸、纵隔气肿等，但病理检查有肺泡过度膨胀和问隔断裂。结论借助APRV—BIPAP模式逐步递增压力组合实施RMs，35／20cmH2O是最佳压力组合，对血流动力学和气道压等影响小；一旦RMs获得疗效满意，设置30／15cm H2O维持20min，RMs疗效好。

Objective To study the effects of APRV （airway pressure release ventilation） / BIPAP（biphasic positive airway pressure） on lung reeruitment/open maneuvers in piglets with acute lung injury. Method The model of acute lung injury （ALI） was induced by E. coli. intrapefitoneal injection in piglets. Based APRV/ BI- PAP model, the different pressure combinations （Phigh/Plow） of RMs increased gradually, such as RMI （30/15）, RM2（35/20）, RM3（40/25）, RM4（45/30）,RM5（50/35）, RM6（55/40）, RM7（60/45） cmH2O. The effects of stepwise RMs were studied by eomputed tomography （CT） at inspiratory phase. Meantime the oxygen index （PaO2/FiO2）, hemodynamie parameter and mean pressure of airway （Pmean） were continuously observed. The piglets were killed when RMs finished and pulmonary pathological examination were done routinely by optical microscope. Data was analyzed by self-contrast method, using SPSS 11.5 software package. Results were expressed as mean ± standard deviation （x ± s ）. Multiple comparisons were made with One-way ANOVA. Pearson correlative analysis was used to describe the relativity of PaO2/FiO2 and the collapsed alveolar area. Changes were considered as statistically significant if P value was less than 0. 05. Results Eight piglets with ALI model were success- fully made and all of them showed different degree of alveolar collapse under chest CT scan. During RMs their PaO2/FiO2 increased obviously （P 〈 0.05） were decreased obviously （P 〈 0.05） too, specially after RM2 finished （ P 〈 0.05）. But the alveolar over-inflation could be found in some non-diseased area. The heart rate （HR） increased and mean artery blood pressure （MAP） decreased significantly while the pressure combinations （ Phigh / Plow） of RMs were added gradually （ P 〈 0.05）. Meantime the Pmean and Ppeak inspiratory pressure （PIP） of air- way and central venous pressure （CVP） were increased significantly （P 〈 0.05）. But when RMs were finished, all of these indexes were back to the levels of pre-RMs. Even there were no barotraumas happened, such as pneu- mothorax and pneumomediastinum, the alveolar overdistention and interruption of the alveolar separation still could be seen by pathologic examination. Conclusions RMs could be done well by APRV/BIPAP. Phigh/Plow （35/20 cmH2O） would be the best pressure combination with more efficacy of RMs and less influence on hemodynamics, airway pressure indexes and others. When the effect of RMs was satisfied enough, setting Phigh/Plow to 30/15 cmH2O for 20 min may maintain the good efficacy of RMs.