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目的 探讨早期急性呼吸窘迫综合征(ARDS)患者采用跨肺压法选择最佳呼气末正压(PEEP)的可行性.方法 采用前瞻性随机自身对照研究方法.选择2013年12月至2015年12月江苏省苏北人民医院外科重症加强治疗病房(ICU)收治的需行机械通气的早期(发病≤3d)ARDS患者.充分肺复张后,调整PEEP至30 cmH2O(1 cmH2O=0.098 kPa),每5 min降低3 cmH2O,直至降为0,在PEEP递减过程中分别采用跨肺压法、最小死腔分数法、最大顺应性法、最佳氧合法选择最佳PEEP,观察最佳PEEP对呼吸力学及气体交换的影响.结果 共纳入28例ARDS患者,男性17例,女性11例;年龄(45±12)岁;急性生理学与慢性健康状况评分系统Ⅱ(APACHEⅡ)评分(21±9)分;氧合指数(PaO2/FiO2)为(165±76)mmHg(1 mmHg=0.133 kPa).①在PEEP递减过程中,跨肺压(Ptp)逐渐下降,PEEP为(9.6±2.3)cmH2O时呼气末跨肺压(Ptp-e)＞0,为(1.3±0.3) cmH2O;而肺静态顺应性(Cst)先逐步改善后有所降低,PEEP为(11.5±2.4)cmH2O时Cst最大,为(50±8)mL/cmH2O.PEEP为(18.0±2.5) cmH2O时PaO2/FiO2最高,为(312±99) mmHg;与Ptp-e 3.00～5.99 cmH2O比较,Ptp-e＜0时PaO2/FiO2显著降低(均P＜ 0.05).PEEP为(10.1±2.2)cmH2O时死腔分数(VD/VT)降至最低,为0.52±0.05;与吸气末跨肺压(Ptp-i)0～2.99 cmH2O时比较,Ptp-i≥15 cmH2O时VD/VT显著增加(均P＜ 0.05).②跨肺压法、最小死腔分数法和最大顺应性法选择的最佳PEEP、Ptp-i、Ptp-e差异均无统计学意义(均P＞0.05),但均明显低于最佳氧合法(均P＜0.05).跨肺压法、最小死腔分数法和最大顺应性法选择最佳PEEP时的Cst较基础状态和最佳氧合法显著改善(mL/cmH2O:46±7、47±9、50±8比30±8和35±10,均P＜0.05).跨肺压法、最小死腔分数法PaO2/FiO2 (mmHg)均高于基础状态(252±86、258±72比165±76,均P＜ 0.05),但明显低于最佳氧合法(312±99,均P＜0.05),而与最大顺应性法(268±85)相比差异无统计学意义(均P＞ 0.05).跨肺压法和最小死腔分数法VD/VT较基础状态和最佳氧合法明显下降(0.53±0.05、0.52±0.05比0.59±0.05、0.58±0.04,均P＜ 0.05).结论 ARDS机械通气患者早期采用跨肺压法选择最佳PEEP,既能促进塌陷肺泡复张,改善氧合和肺顺应性,又不会导致肺泡过度膨胀.

Objective To evaluate the value of transpulmonary pressure (Ptp) guided optimal positive end-expiratory pressure (PEEP) selection in patients with early acute respiratory distress syndrome (ARDS).Methods A prospective randomized self-control study was conducted.ARDS patients in the early stage (onset ≤3 days) undergoing intubation and mechanical ventilation admitted to intensive care unit (ICU) of Jiangsu Provincial Subei People's Hospital from December 2013 to December 2015 were enrolled.The PEEP level was regulated to 30 cmH2O (1 cmH2O =0.098 kPa) after recruitment maneuver,and then it was gradually decreased to 0 with lowering by 3 cmH2O every 5 minutes.The optimal PEEP was titrated by Ptp,lowest dead space fraction (VD/VT),highest static lung compliance (Cst),and optimal oxygenation,respectively.Parameters of respiratory mechanics and gas exchange were observed.Results Totally 28 patients with ARDS (including 17 male and 11 female) were included with the average age of (45 ± 12) years old,acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score was 21 ± 9,oxygenation index (PaO2/FiO2) was (165 ± 76) mmHg (1 mmHg =0.133 kPa).① During decremental PEEP titration,Ptp was gradually decreased,and expiratory Ptp (Ptp-e) was more than zero [(1.3±0.3) cmH2O] when PEEP was (9.6 ± 2.3) cmH2O.Cst was initially improved until reaching a peak,and then deteriorated.Cst was highest [(50 ± 8) mL/cmH2O] when PEEP was (11.5 ± 2.4) cmH2O.PaO2/FiO2 reached the maximum [(312 ± 99) mmHg] at PEEP level of (18.0 ± 2.5) cmH2O.Compared with Ptp-e 3.00-5.99 cmH2O,PaO2/FiO2 was significantly decreased when Ptp-e became negative (all P ＜ 0.05).VD/VT was lowest (0.52 ±0.05) when PEEP was (10.1 ± 2.2) cmH2O.When compared with ventilation [inspiratory Ptp (Ptp-i) 0-2.99 cmH2O],it was significantly higher during high (Ptp-i ≥ 15 cmH2O,all P ＜ 0.05).② There were no statistically significant differences in the levels of optimal PEEP,Ptp-i and Ptp-e among Ptp,lowest VD/VT and highest Cst methods (all P ＞ 0.05),but they were significantly less than optimal oxygenation method (all P ＜ 0.05).Compared with baseline and the method of optimal oxygenation,Cst in other three PEEP titration methods including Ptp,lowest VD/VT and highest Cst was improved obviously (mL/cmH2O:46± 7,47±9,50± 8 vs.30± 8,35 ± 10,all P ＜ 0.05).PaO2/FiO2 (mmHg) in the method of Ptp and lowest VD/VT were higher than the baseline (252 ± 86,258 ± 72 vs.165 ± 76,both P ＜ 0.05),but significantly lower than that of optimal oxygenation method (312 ± 99,both P ＜ 0.05),and did not significantly differ from that of highest Cst (268± 85,both P ＞ 0.05).Compared with baseline and the method of optimal oxygenation,VD/Vr improved significantly in ventilated patients on PEEP targeting with Ptp and lowest VD/VT (0.53±0.05,0.52±0.05 vs.0.59±0.05,0.58±0.04,all P ＜ 0.05).Conclusion Titration the optimal PEEP level with the method of Ptp could promote collapse alveolar recruitment,improve oxygenation and lung compliance,decrease dead space ventilation,and will not cause alveolar excessive inflation in patients who undergoing mechanical ventilation with early ARDS.