Department of Anaesthesiology and Critical Care, Hotel-Dieu Hospital, University Hospital of Clermont-Ferrand, Clermont-Ferrand, France.
Eur J Anaesthesiol. 2010 Jun;27(6):508-13. doi: 10.1097/EJA.0b013e3283398806.
Induction of anaesthesia promotes collapse of dependent lung regions in both obese and nonobese patients. We hypothesized that end-expiratory lung volume (EELV) may be more sensitive than oxygenation to evaluate the effects of positive end-expiratory pressure (PEEP) after anaesthesia induction.
Forty patients (20 nonobese patients and 20 obese patients) were prospectively studied. After anaesthesia induction, PEEP was adjusted in a stepwise fashion [zero end-expiratory pressure (ZEEP), PEEP 5 cmH2O and PEEP 10 cmH2O]. At each step, we measured EELV, static elastance, gas exchange and dead space. Other than changing PEEP, respiratory settings were kept constant throughout.
Anaesthesia induction and ZEEP both lowered EELV by 39% in nonobese patients and 59% in obese patients (both P < 0.05), as well as oxygenation (P < 0.05). Compared with ZEEP, in nonobese patients, PEEP 5 cmH2O and PEEP 10 cmH2O improved EELV (+15 and +40%, respectively, P < 0.01) and elastance but not oxygenation. In obese patients, PEEP 10 cmH2O also improved EELV (49% vs. ZEEP and 30% vs. PEEP 5 cmH2O, P < 0.01), elastance and dead-space fraction, with no effect on oxygenation. PEEP-induced changes of EELV correlated with changes of elastance (r = 0.46, P = 0.003), but not with oxygenation.
After induction of anaesthesia, mechanical ventilation with ZEEP is associated with a profound reduction in EELV. PEEP improves efficiently EELV and respiratory mechanics, with no major effect on oxygenation. EELV may be a useful indicator to guide PEEP setting in the operating room.
麻醉诱导可导致肥胖和非肥胖患者的依赖肺区萎陷。我们假设呼气末肺容积（EELV）可能比氧合更敏感，可用于评估麻醉诱导后呼气末正压（PEEP）的效果。
前瞻性研究 40 例患者（20 例非肥胖患者和 20 例肥胖患者）。麻醉诱导后，逐步调整 PEEP[零呼气末正压（ZEEP）、PEEP 5 cmH2O 和 PEEP 10 cmH2O]。在每一步，我们测量 EELV、静态顺应性、气体交换和死腔。除了改变 PEEP 外，整个过程中呼吸设置保持不变。
麻醉诱导和 ZEEP 使非肥胖患者和肥胖患者的 EELV 分别降低 39%和 59%（均 P < 0.05），以及氧合（P < 0.05）。与 ZEEP 相比，在非肥胖患者中，PEEP 5 cmH2O 和 PEEP 10 cmH2O 改善了 EELV（分别增加 15%和 40%，均 P < 0.01）和顺应性，但不改善氧合。在肥胖患者中，PEEP 10 cmH2O 也改善了 EELV（与 ZEEP 相比，49%；与 PEEP 5 cmH2O 相比，30%，均 P < 0.01）、顺应性和死腔分数，对氧合无影响。EELV 的 PEEP 诱导变化与顺应性的变化相关（r = 0.46，P = 0.003），但与氧合无关。
麻醉诱导后，使用 ZEEP 的机械通气会导致 EELV 显著降低。PEEP 可有效改善 EELV 和呼吸力学，但对氧合影响不大。EELV 可能是指导手术室 PEEP 设置的有用指标。
