俯卧位时间不足不能有效改善急性呼吸窘迫综合征／急性肺损伤时的氧合状态

目的比较24h内不同俯仰卧位辅助通气时间对急性呼吸窘迫综合征／急性肺损伤（ARDS／ALI）时氧合状态和血液动力学的影响。方法健康雌性小型猪15只，经气管插管注射盐酸制备ARDS模型，随机均分为俯卧8h＋仰卧16h组（8h组）、俯卧16h＋仰卧8h组（16h组）、持续俯卧24h组（24h组）。每4h测量动脉血气、心排量（CO）和肺动脉楔压（PAWP），计算氧合指数（PaO2/FiO2）和心脏指数（CI），记录24h内动物死亡的情况。结果3组模型在制模前PaO2/FiO2均〉300mmHg，制模成功时的PaO2/FiO2均≤200mmHg。3组模型在实施肺保护性通气和体位治疗后PaO2/FiO2均呈上升趋势。16h组与24h组动物氧合指数的改善优于8h组动物（均P〈0．05）；3组动物的血液动力学指标24h变化在正常范围，组间差异无统计学意义（均P〉0．05）。结论每天实施8h俯卧位辅助通气不能有效改善ARDS／ALI时的氧合状态，早期足量（16h或以上）的俯卧位辅助通气可以安全有效地提高氧合，并有望降低病死率。

Insufficient length of prone position during ventilation fails to effectively improve oxygenation in acute respiratory distress syndrome/acute lung injury

Objective To compare the effects of different lengths of duration of prone and supine position on the oxygenation and hemodynamics during 24-hour period in acute respiratory distress syndrome/acute lung injury （ARDS/ALI）. Methods Fifteen fenmle mini-pigs underwent intratrachcal infusion of hydrochloric acid so as to establish ARDS/AL1 models and then assigned randomly into 3 equal groups： 8h group （put in prone position for 8h and then in supine position for 16h）, 16h group （in proue position for 16h and then in supine position for 8h）, and 24h group （in prone position for 24h continuously）. Arterial blood gases, puhnonary artery wedge pressure （PAWP）, and cardiac index （CI） were measured every four hours for a period of 24 hours. Arterial oxygenation efficiency （PaO2/FiO2）and cardiac index （CI） were calculated. The survival of the animals was observed for 24h. Results The PaO2/FiO2 values of the 3 groups before the establishment of models were all 〉300 mmHg, all became ≤ 200 mmHg after the establishment of models, and all increased after the protective lung ventilation and body posture therapy. The improvement in PaO~fFiO2 level was significantly better in the 16h group and 24h group than in the 8h group （both P 〈 0.05）, whereas there were no significant differences in PAWP and C1 levels among these 3 groups （all P 〉 0.05）. Conclusion Eight-hour prone position a day fails to effectively improve the oxygenation in ARDS/ALI. However, early prone position for 16 hours or longer is safe and effective in improving oxygenation, and may reduce the mortality.