Expiratory washout versus optimization of mechanical ventilation during permissive hypercapnia in patients with severe acute respiratory distress syndrome
Expiratory washout versus optimization of mechanical ventilation during permissive hypercapnia in patients with severe acute respiratory distress syndrome
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DOI：
10.1164/ajrccm.160.1.9809006
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发表时间：
1999-07-01
影响因子：
24.7
通讯作者：
Rouby, JJ
中科院分区：
文献类型：
--
作者：
Richecoeur, J;Lu, Q;Rouby, JJ
本研究的目的是比较三种降低严重急性呼吸窘迫综合征患者Pa-CO2的缓解技术，这些患者接受了允许性高碳酸血症治疗：（1）流速为15 L/min的单独呼气冲洗，（2）优化的机械通气，定义为呼吸频率增加到可能的最大速率，而不产生固有呼气末正压（PEEP）与减少仪器死腔相结合，以及（3）两种方法的组合。根据压力-容积曲线设定潮气量，以获得吸气平台气道压力，等于在将PEEP设定为下拐点以上2 cm H2O后的上拐点减去2 cm H2O，并在整个研究期间保持恒定。通过调整外源性PEEP，在相同的吸气平台气道压下比较三种模式。在使用呼吸频率为18次/min的常规机械通气期间，观察到呼吸性酸中毒（Pa-CO2 = 84 +/- 24 mm Hg，pH = 7.21 +/- 0.12）。呼气冲洗和优化的机械通气（呼吸频率为30 +/- 4次呼吸/min）对CO2消除的影响相似（Δ Pa-CO2 = -28 +/- 11% vs-27 +/- 12%）。当两种方法联合使用时，观察到Pa-CO2进一步降低（Δ Pa-CO2 = -46 +/- 7%）。在呼气冲洗期间，外源性PEEP必须减少5.3 +/- 2.1 cm H2O，在两种模式的组合期间，外源性PEEP必须减少7.3 +/- 1.3 cm H2O，而在单独优化机械通气期间，外源性PEEP保持不变。总之，在重度ARDS和允许性高碳酸血症患者中，常规机械通气期间增加呼吸频率和减少仪器死腔与呼气冲洗一样有效，可降低Pa-CO2。当结合使用时，这两种技术具有相加效应，并导致Pa-CO2水平接近正常值。
The aim of this study was to compare three ventilatory techniques for reducing Pa-CO2 in patients with severe acute respiratory distress syndrome treated with permissive hypercapnia: (1) expiratory washout alone at a flow of 15 L/min, (2) optimized mechanical ventilation defined as an increase in the respiratory frequency to the maximal rate possible without development of intrinsic positive end-expiratory pressure (PEEP) combined with a reduction of the instrumental dead space, and (3) the combination of both methods. Tidal volume was set according to the pressure-volume curve in order to obtain an inspiratory plateau airway pressure equal to the upper inflection point minus 2 cm H2O after setting the PEEP at 2 cm H2O above the lower inflection point and was kept constant throughout the study. The three modalities were compared at the same inspiratory plateau airway pressure through an adjustment of the extrinsic PEEP. During conventional mechanical ventilation using a respiratory frequency of 18 breaths/min, respiratory acidosis (Pa-CO2 = 84 +/- 24 mm Hg and pH = 7.21 +/- 0.12) was observed. Expiratory washout and optimized mechanical ventilation (respiratory frequency of 30 +/- 4 breaths/min) had similar effects on CO2 elimination (Delta Pa-CO2 = -28 +/- 11% versus -27 +/- 12%). A further decrease in Pa-CO2 was observed when both methods were combined (Delta Pa-CO2 = -46 +/- 7%). Extrinsic PEEP had to be reduced by 5.3 +/- 2.1 cm H2O during expiratory washout and by 7.3 +/- 1.3 cm H2O during the combination of the two modes, whereas it remained unchanged during optimized mechanical ventilation alone. In conclusion, increasing respiratory rate and reducing instrumental dead space during conventional mechanical ventilation is as efficient as expiratory washout to reduce Pa-CO2 in patients with severe ARDS and permissive hypercapnia. When used in combination, both techniques have additive effects and result in Pa-CO2 levels close to normal values.