不同呼气末正压水平对绵羊急性呼吸窘迫综合征模型肺复张效果及血流动力学的影响

目的观察在绵羊急性呼吸窘迫综合征（ARDS）模型上利用控制性肺膨胀（SI）实施肺复张策略后不同呼气末正压（PEEP）水平对复张效果及血流动力学的影响，以找到理想的PEEP压力范围。方法12只绵羊在麻醉后，行纤维支气管镜温生理盐水肺泡灌洗复制ARDS模型，低流速法描记准静态压力-容积（P-V）曲线，寻找P-V曲线的上拐点（UIP），并以UIP下5cm H2O（1cm H2O=0．098kPa）作为SI的峰压进行肺复张，肺复张后根据不同的PEEP水平分为PEEP5、PEEP10、PEEP15、PEEP20组。记录肺复张后2h内的血流动力学参数及氧代谢指标，实验后进行肺组织活检，观察SI后不同的PEEP水平对血流动力学及复张效果的影响。结果PEEP5组和PEEP10组在复张后2h内对血流动力学没有影响，但PEEP5组氧合呈现下降趋势，病理显示肺泡组织仍轻度萎陷，伴灶性肺泡塌陷；PEEP≥15cm H2O时中心静脉压（cVP）明显升高，心排血指数（CI）明显降低，氧合指数、肺机械参数均较复张前明显改善并保持2h以上。结论ARDS肺复张后，PEEP设定在10-20cm H2O可以明显改善氧合，对正常心功能状态下的血流动力学影响并不显著。

Effects of different levels of positive end expiratory pressure on lung recruitment and hemodynamics after sustained inflation in acute respiratory distress syndrome in sheep

OBJECTIVE: To study the effects of different levels of positive end expiratory pressure (PEEP) on recruitment and hemodynamics after sustained inflation in acute respiratory distress syndrome (ARDS) in sheep. METHODS: Twelve adult sheep were anaesthetized and ARDS was induced by lung lavage with warm normal saline. Pressure-volume (P-V) curves were traced using the low flow technique and the upper inflection point (UIP) was determined. Sustained inflation was exercised at the pressure of 5 cm H(2)O (1 cm H(2)O=0.098 kPa) below UIP, and the sheep were divided into groups according to different PEEP levels (PEEP5, PEEP10, PEEP15, PEEP20). Hemodynamics and lung mechanics values were recorded during the 2 hours of recruitment, and biopsy was performed at the end of the trial. RESULTS: There was no effect on hemodynamics and recruitment in 2 hours in PEEP5 and PEEP10 groups, but oxygenation was found to be decreased in PEEP5 group, and focal alveolar collapse was found in pathological examination. When the PEEP level reached 15 cm H(2)O, there was significant elevation in central venous pressure (CVP), and cardiac index (CI) fell remarkably, but oxygenation index and lung mechanics were improved and stable in 2 hours. CONCLUSION: Our study demonstrates that it can obviously improve oxygenation when PEEP is set at 10-20 cm H(2)O, oxygenation can be obviously improved, with little disturbance to hemodynamics in case cardiac function is normal.