呼气末正压通气可以将非腹部手术的肺不张量减少到最低：随机对照试验
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Positive End-expiratory Pressure Alone Minimizes Atelectasis Formation in Nonabdominal Surgery ：A Randomized Controlled Trial
背景与目的
对于接受全身麻醉的病人，越来越多的人建议采用各种保护通气的方法。然而，每个组成部分的重要性仍不清楚。特别是，呼气末正压通气在围手术期使用仍然存在争议。作者检测单纯PEEP足以限制非腹部手术期间肺不张形成的假设是否成立。
方 法
这是一项临床随机盲法对照试验。24名接受全身麻醉并机械通气的健康患者根据体重指数随机接受PEEP 7或9 cm H2O（n = 12）或不接受PEEP（n = 12）。没有使用肺复张通气策略。主要结果是手术结束前通过计算机断层技术在横膈膜附近扫描肺不张区域。并且测量血气分析动脉氧分压与吸入氧浓度(PaO2/FiO2)比值来评估氧合。
结 果
在手术结束时，肺不张区占肺总面积的百分比在peep组和无peep组分别是1.8（0.3~9.9）、4.6（1~10.2）。中位数的差异是2.8%（95%CI，1.7%到5.7%;P = 0.002)。氧合和二氧化碳消除维持在PEEP组中，但两者均在无PEEP组中恶化。
结 论
在非腹部手术中，充足的peep足以将健康肺的肺不张量降到最低，从而维持氧合。因此，常规肺复张通气策略似乎没有必要，作者建议，只有在明确指出的情况下，才应该使用。
原始文献摘要
Östberg E, Thorisson A, Enlund M, et al. Positive End-expiratory Pressure Alone Minimizes Atelectasis Formation in Nonabdominal Surgery:A Randomized Controlled Trial | Anesthesiology | ASA Publications[J]. Anesthesiology, 2018:1.
Background: Various methods for protective ventilation are increasingly being recommended for patients undergoing general anesthesia. However, the importance of each individual component is still unclear. In particular, the perioperative use of positive end-expiratory pressure (PEEP) remains controversial. The authors tested the hypothesis that PEEP alone would be sufficient to limit atelectasis formation during nonabdominal surgery.
Methods: This was a randomized controlled evaluator-blinded study. Twenty-four healthy patients undergoing general anesthesia were randomized to receive either mechanical ventilation with PEEP 7 or 9 cm H2O depending on body mass index (n = 12) or zero PEEP (n = 12). No recruitment maneuvers were used. The primary outcome was atelectasis area as studied by computed tomography in a transverse scan near the diaphragm, at the end of surgery, before emergence. Oxygenation was evaluated by measuring blood gases and calculating the ratio of arterial oxygen partial pressure to inspired oxygen fraction (PaO2/FIO2 ratio).
Results: At the end of surgery, the median (range) atelectasis area, expressed as percentage of the total lung area, was 1.8 (0.3 to 9.9) in the PEEP group and 4.6 (1.0 to 10.2) in the zero PEEP group. The difference in medians was 2.8% (95% CI, 1.7 to 5.7%; P = 0.002). Oxygenation and carbon dioxide elimination were maintained in the PEEP group, but both deteriorated in the zero PEEP group.
Conclusions: During nonabdominal surgery, adequate PEEP is sufficient to minimize atelectasis in healthy lungs and thereby maintain oxygenation. Thus, routine recruitment maneuvers seem unnecessary, and the authors suggest that they should only be utilized when clearly indicated.
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