肥胖患者术中机械通气的个体化与固定化呼气末正压的比较：一项二次分析

全身麻醉可能导致肥胖患者肺不张和氧合恶化。作者假设，与固定的呼气末正压(PEEP)相比，个体化呼气末正压可改善术中氧合和通气分布。

这项二次分析包括在莱比锡大学医院进行的肥胖患者多中心术中保护性通气（PROBESE）试验（n=42）和本地单中心试验（n=54）的所有肥胖患者。两项试验的入选标准均为选择性腹腔镜腹部手术，体重指数大于或等于35kg/m²，在PROBESE研究中，患者被随机分为4cmH₂O的PEEP组（n=19）和12cmH₂O的PEEP组（n=21）。在单中心研究中，他们被随机分为5cmH₂O的PEEP（n=25）或遵循依靠电阻抗断层扫描确定个体化PEEP（n=25）的招募策略。主要观察指标为拔管前PaO₂/吸入氧分数，次要观察指标为依赖肺的分布和驱动压的术中潮气量。

90例患者在合并两个较低PEEP组后分为三组进行评估。个体化PEEP的中位数为18（四分位间距16~22；范围，10~26）cmH₂O。拔管前PaO₂/吸氧分数分别为515（个体PEEP）、370（固定PEEP为12cmH₂O）和305（固定PEEP为4～5cmH₂O）mmHg（与个体PEEP差异为145；95%CI，91～200；12cmH₂O和210的固定PEEP值P<0.001；对于4~5cmH₂O的固定PEEP的95%CI，164～257；P<0.001。依赖肺区术中潮气量分别为43.9%（个体化PEEP）、25.9%（固定PEEP为12cmH₂O）和26.8%（固定PEEP为4~5cmH₂O）（与个体化PEEP差异18.0%；95%CI，8.0～20.7；固定PEEP为12cmH₂O时P<0.001，17.1%；对于4~5cmH₂O的固定PEEP，95%CI，10.0～20.6；P<0.001。术中平均驱动压为9.85cmH₂O（个体化PEEP）、14.45cmH₂O（固定PEEP为12cmH2O）和18.85cmH₂O（固定PEEP为4～5cmH2O），P<0.001。

这项对接受腹腔镜手术的肥胖患者的二次分析发现，通过使用个性化PEEP电阻抗断层扫描测量，可以获得更好的氧合，更低的驱动压力，以及通气量向依赖肺区的重新分布。但这对患者预后的影响尚不清楚。

Individualized versus Fixed Positive End-expiratory Pressure for Intraoperative Mechanical Ventilation in Obese Patients: A Secondary Analysis

Abstract

Background: General anesthesia may cause atelectasis and deterioration in oxygenation in obese patients. The authors hypothesized that individualized positive end-expiratory pressure (PEEP) improves intraoperative oxygenation and ventilation distribution compared to fixed PEEP

Methods: This secondary analysis included all obese patients recruited at University Hospital of Leipzig from the multicenter Protective Intraoperative Ventilation with Higher versus Lower Levels of Positive End-Expiratory Pressure in Obese Patients (PROBESE) trial (n=42) and likewise all obese patients from a local single-center trial (n=54). Inclusion criteria for both trials were elective laparoscopic abdominal surgery, body mass index greater than or equal to 35 kg/m², and Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) score greater than or equal to 26. Patients were randomized to PEEP of 4 cm H₂O (n=19) or a recruitment maneuver followed by PEEP of 12 cmH₂O (n=21) in the PROBESE study. In the single-center study, they were randomized to PEEP of 5 cmH₂O (n=25) or a recruitment maneuver followed by individualized PEEP (n=25) determined by electrical impedance tomography. Primary endpoint was Pao2/inspiratory oxygen fraction before extubation and secondary endpoints included intraoperative tidal volume distribution to dependent lung and driving pressure.

Results: Ninety patients were evaluated in three groups after combining the two lower PEEP groups. Median individualized PEEP was 18 (interquartile range, 16 to 22; range, 10 to 26) cmH₂O. PaO₂/inspiratory oxygen fraction before extubation was 515 (individual PEEP), 370 (fixed PEEP of 12 cmH₂O), and 305 (fixed PEEP of 4 to 5 cmH₂O) mmHg (difference to individualized PEEP , 145; 95% CI, 91 to 200; P < 0.001 for fixed PEEP of 12 cmH₂O and 210; 95% CI, 164 to 257; P < 0.001 for fixed PEEP of 4 to 5 cmH₂O). Intraoperative tidal volume in the dependent lung areas was 43.9% (individualized PEEP), 25.9% (fixed PEEP of 12 cmH₂O) and 26.8% (fixed PEEP of 4 to 5 cmH₂O) (difference to individualized PEEP: 18.0%; 95% CI, 8.0 to 20.7; P < 0.001 for fixed PEEP of 12 cmH₂O and 17.1%; 95% CI, 10.0 to 20.6; P < 0.001 for fixed PEEP of 4 to 5 cmH₂O). Mean intraoperative driving pressure was 9.8 cmH₂O (individualized PEEP), 14.4 cmH₂O (fixed PEEP of 12 cmH₂O), and 18.8 cmH₂O (fixed PEEP of 4 to 5 cmH₂O), P < 0.001.

Conclusions: This secondary analysis of obese patients undergoing laparoscopic surgery found better oxygenation, lower driving pressures, and redistribution of ventilation toward dependent lung areas measured by electrical impedance tomography using individualized PEEP . The impact on patient outcome remains unclear.