绵羊急性呼吸窘迫综合征开放肺压力安全性的实验研究

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法（SI）实施肺复张策略对血流动力学及肺组织结构的影响，以期找到实施SI的理想压力及时间范围。方法14只绵羊在全麻下行纤维支气管镜温生理盐水肺泡灌洗建立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）以及下拐点（LIP）。以UIP下5cm H2O（1cm H2O=0．098kPa）、UIP、UIP上10cm H2O和UIP上20cm H2O将14只绵羊随机分为4组（U-5、U＋0、U＋10、U＋20组），并作为SI的峰压进行肺复张，持续时间为60s，记录每次复张过程中及复张后连续血流动力学参数和氧合指数变化，维持至2h后实验结束，行CT、肺组织病理学检查。结果U＋20组在SI过程中出现气胸，导致绵羊死亡；其余各组肺复张过程中，对血流动力学均有明显影响。U＋10组肺复张10s即出现中心静脉压（CVP）升高，心排血量（CO）、心脏指数（CI）、平均血压（MBP）明显下降，复张后CI恢复缓慢；U＋0组及U-5组可完成整个肺复张过程，CVP轻度升高，CO、CI下降，U-5组在复张结束后15s、U＋0组在复张结束后30s恢复至复张前水平。肺组织病理学观察仍见U＋0组有肺大泡形成。结论对ARDS实施肺复张，应充分考虑压力对血流动力学及肺组织的损害；肺复张压力应选择在UIP或UIP下5cm H2O，此时对血流动力学没有明显影响。

Experimental study of the safety of sustained inflation strategy in acute respiratory distress syndrome in sheep

Objective To evaluate the effects of lung recruitment maneuver (RM) on hemodynamics and lung structure with sustained inflation (SI) in acute respiratory distress syndrome (ARDS) in sheep, to look for a safe range of pressure and time of SI. Methods Fourteen anaesthetized sheep were subjected to lung lavage through a branchofibroscope to reproduce ARDS, and quasistatic pressurevolume (PV ) curves were obtained with low flow technique. The upper inflection point (UIP) and the lower inflection point (LIP) were found, and then 5 cm H_2O (1 cm H_2O=0.098 kPa) below UIP, UIP, 10 cm H_2O above UIP, 20 cm H_2O above UIP as the peak pressure of SI were selected as the test pressure. They were randomized to four groups (U-5, U+0, U+10, U+20).The duration of SI was 60 seconds. Hemodynamics and oxygenation indexes were monitored and recorded during and after SI until the study was terminated 2 hours later, then CT and lung tissue biopsy were performed. Results Pneumothorax was found in U+20 group, resulting in the death of sheep. Hemodynamics was affected significantly in other groups during SI. In U+10 group, cardiac output (CO) and cardiac index (CI) were lowered at 15 seconds after RM began, and recovered slowly after RM; in U+0 group and U5 group, the entire RM could be carried out to the end, and biopsy showed bullous emphysema in U+0 group. Conclusion The impairment of the hemodynamics and damage to the lung structure should be prevented when RM is performed in ARDS patients, and the inflation pressure should be limited within the range of UIP or 5 cm H_2O under UIP to avoid adverse effect on hemodynamics.