From the Department of Anesthesia, Critical Care and Pain Medicine (J.F., R.R.S.S., M.T.D., C.Z., L.B.) the Respiratory Care Department (R.M.K.) the Department of Radiology (F.J.F., F,M.T.), Massachusetts General Hospital, Boston, Massachusetts the Pulmonary Division, Cardio-Pulmonary Department, Heart Institute (Incor), Hospital Das Clínicas, Faculty of Medicine, University of Sao Paulo, São Paulo, Brazil (C.C.A.M., M.B.P.A.). Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Respiratory Care Department, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.
Anesthesiology. 2019 May;130(5):791-803. doi: 10.1097/ALN.0000000000002638.
Obese patients are characterized by normal chest-wall elastance and high pleural pressure and have been excluded from trials assessing best strategies to set positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS). The authors hypothesized that severely obese patients with ARDS present with a high degree of lung collapse, reversible by titrated PEEP preceded by a lung recruitment maneuver.
Severely obese ARDS patients were enrolled in a physiologic crossover study evaluating the effects of three PEEP titration strategies applied in the following order: (1) PEEPARDSNET: the low PEEP/FIO2 ARDSnet table; (2) PEEPINCREMENTAL: PEEP levels set to determine a positive end-expiratory transpulmonary pressure; and (3) PEEPDECREMENTAL: PEEP levels set to determine the lowest respiratory system elastance during a decremental PEEP trial following a recruitment maneuver on respiratory mechanics, regional lung collapse, and overdistension according to electrical impedance tomography and gas exchange.
Fourteen patients underwent the study procedures. At PEEPARDSNET (13 ± 1 cm H2O) end-expiratory transpulmonary pressure was negative (-5 ± 5 cm H2O), lung elastance was 27 ± 12 cm H2O/L, and PaO2/FIO2 was 194 ± 111 mmHg. Compared to PEEPARDSNET, at PEEPINCREMENTAL level (22 ± 3 cm H2O) lung volume increased (977 ± 708 ml), lung elastance decreased (23 ± 7 cm H2O/l), lung collapse decreased (18 ± 10%), and ventilation homogeneity increased thus rising oxygenation (251 ± 105 mmHg), despite higher overdistension levels (16 ± 12%), all values P < 0.05 versus PEEPARDSnet. Setting PEEP according to a PEEPDECREMENTAL trial after a recruitment maneuver (21 ± 4 cm H2O, P = 0.99 vs. PEEPINCREMENTAL) further lowered lung elastance (19 ± 6 cm H2O/l) and increased oxygenation (329 ± 82 mmHg) while reducing lung collapse (9 ± 2%) and overdistension (11 ± 2%), all values P < 0.05 versus PEEPARDSnet and PEEPINCREMENTAL. All patients were maintained on titrated PEEP levels up to 24 h without hemodynamic or ventilation related complications.
Among the PEEP titration strategies tested, setting PEEP according to a PEEPDECREMENTAL trial preceded by a recruitment maneuver obtained the best lung function by decreasing lung overdistension and collapse, restoring lung elastance, and oxygenation suggesting lung tissue recruitment.
肥胖患者的胸壁弹性正常，胸膜压力高，已被排除在评估急性呼吸窘迫综合征（ARDS）中设置最佳呼气末正压（PEEP）策略的试验之外。作者假设，ARDS 合并严重肥胖的患者存在高度肺塌陷，通过滴定 PEEP 可以逆转，滴定前先进行肺复张手法。
严重肥胖的 ARDS 患者被纳入一项生理交叉研究，评估了三种 PEEP 滴定策略的效果，按以下顺序应用：（1）PEEPARSDNET：低 PEEP/FIO2 ARDSnet 表；（2）PEEPINCREMENTAL：设置 PEEP 水平以确定正性呼气末跨肺压；（3）PEEPDECREMENTAL：在根据电阻抗断层成像和气体交换确定机械呼吸、区域性肺塌陷和过度膨胀的递减 PEEP 试验后，设置 PEEP 水平以确定最低呼吸系统弹性。
14 名患者接受了研究程序。在 PEEPARSDNET（13 ± 1 cm H2O）呼气末跨肺压为负（-5 ± 5 cm H2O），肺弹性为 27 ± 12 cm H2O/L，PaO2/FIO2 为 194 ± 111 mmHg。与 PEEPARSDNET 相比，在 PEEPINCREMENTAL 水平（22 ± 3 cm H2O）时，肺容量增加（977 ± 708 ml），肺弹性降低（23 ± 7 cm H2O/L），肺塌陷减少（18 ± 10%），通气均匀性增加，从而提高氧合（251 ± 105 mmHg），尽管过度充气水平较高（16 ± 12%），所有值 P < 0.05 均与 PEEPARSDNET 相比。在招募手法后进行 PEEPDECREMENTAL 试验设置 PEEP（21 ± 4 cm H2O，P = 0.99 与 PEEPINCREMENTAL）进一步降低肺弹性（19 ± 6 cm H2O/L）并增加氧合（329 ± 82 mmHg），同时降低肺塌陷（9 ± 2%）和过度充气（11 ± 2%），所有值 P < 0.05 与 PEEPARSDNET 和 PEEPINCREMENTAL 相比。所有患者在 24 小时内均维持滴定 PEEP 水平，无血流动力学或通气相关并发症。
在测试的 PEEP 滴定策略中，通过招募手法前进行 PEEPDECREMENTAL 试验设置 PEEP，通过降低肺过度充气和塌陷，恢复肺弹性和氧合，从而获得最佳的肺功能，提示肺组织募集。
