Rusca Marco, Proietti Stefania, Schnyder Pierre, Frascarolo Philippe, Hedenstierna Göran, Spahn Donat R, Magnusson Lennart
Departments of *Anesthesiology and †Diagnostic Radiology, University Hospital, Lausanne, Switzerland; and ‡Department of Clinical Physiology, University Hospital, Uppsala, Sweden.
Anesth Analg. 2003 Dec;97(6):1835-1839. doi: 10.1213/01.ANE.0000087042.02266.F6.
General anesthesia promotes atelectasis formation, which is augmented by administration of large oxygen concentrations. We studied the efficacy of positive end-expiratory pressure (PEEP) application during the induction of general anesthesia (fraction of inspired oxygen [FIO(2)] 1.0) to prevent atelectasis. Sixteen adult patients were randomly assigned to one of two groups. Both groups breathed 100% O(2) for 5 min and, after a general anesthesia induction, mechanical ventilation via a face mask with a FIO(2) of 1.0 for another 5 min before endotracheal intubation. Patients in the first group (PEEP group) had continuous positive airway pressure (CPAP) (6 cm H(2)O) and mechanical ventilation via a face mask with a PEEP of 6 cm H(2)O. No CPAP or PEEP was applied in the control group. Atelectasis, determined by computed radiograph tomography, and analysis of blood gases were measured twice: before the beginning of anesthesia and directly after the intubation. There was no difference between groups before the anesthesia induction. After endotracheal intubation, patients in the control group showed an increase of the mean area of atelectasis from 0.8% +/- 0.9% to 4.1% +/- 2.0% (P = 0.0002), whereas the patients of the PEEP group showed no change (0.5% +/- 0.6% versus 0.4% +/- 0.7%). After the intubation with a FIO(2) of 1.0, PaO(2) was significantly higher in the PEEP group than in the control (591 +/- 54 mm Hg versus 457 +/- 99 mm Hg; P = 0.005). Atelectasis formation is prevented by application of PEEP during the anesthesia induction despite the use of large oxygen concentrations, resulting in improved oxygenation.
Application of positive end-expiratory pressure during the induction of general anesthesia prevents atelectasis formation. Furthermore, it improves oxygenation and probably increases the margin of safety before intubation. Therefore, this technique should be considered for all anesthesia induction, at least in patients at risk of difficult airway management during the anesthesia induction.
全身麻醉会促进肺不张的形成，高浓度吸氧会加剧这种情况。我们研究了在全身麻醉诱导期间（吸入氧分数[FIO₂]为1.0）应用呼气末正压（PEEP）预防肺不张的效果。16例成年患者被随机分为两组。两组均吸入100%氧气5分钟，在全身麻醉诱导后，经面罩机械通气，吸入氧分数为1.0，持续5分钟，然后进行气管插管。第一组（PEEP组）患者持续气道正压（CPAP）（6 cmH₂O），经面罩机械通气，PEEP为6 cmH₂O。对照组未应用CPAP或PEEP。通过计算机断层扫描确定肺不张情况，并在麻醉开始前和插管后立即两次测量血气。麻醉诱导前两组之间无差异。气管插管后，对照组患者肺不张平均面积从0.8%±0.9%增加到4.1%±2.0%（P = 0.0002），而PEEP组患者无变化（0.5%±0.6%对0.4%±0.7%）。在吸入氧分数为1.0的情况下插管后，PEEP组的动脉血氧分压（PaO₂）显著高于对照组（591±54 mmHg对457±99 mmHg；P = 0.005）。尽管使用高浓度氧气，但在麻醉诱导期间应用PEEP可预防肺不张的形成，从而改善氧合。
在全身麻醉诱导期间应用呼气末正压可预防肺不张的形成。此外，它可改善氧合，并可能增加插管前的安全边际。因此，对于所有麻醉诱导，至少对于麻醉诱导期间气道管理困难风险较高的患者，应考虑采用该技术。
