Ranieri V M, Mascia L, Fiore T, Bruno F, Brienza A, Giuliani R
Istituto di Anestesiologia e Rianimazione, Ospedale Policlinico, Università di Bari, Italy.
Anesthesiology. 1995 Oct;83(4):710-20. doi: 10.1097/00000542-199510000-00010.
In patients with acute respiratory distress syndrome (ARDS), the ventilatory approach is based on tidal volume (VT) of 10-15 ml/kg and positive end-expiratory pressure (PEEP). To avoid further pulmonary injury, decreasing VT and allowing PaCO2 to increase (permissive hypercapnia) has been suggested. Effects of 10 cmH2O of PEEP on respiratory mechanics, hemodynamics, and gas exchange were compared during mechanical ventilation with conventional (10-15 ml/kg) and low (5-8 ml/kg) VT.
Nine sedated and paralyzed patients were studied. VT was decreased gradually (50 ml every 20-30 min). Static volume-pressure (V-P) curves, hemodynamics, and gas exchange were measured.
During mechanical ventilation with conventional VT, V-P curves on PEEP 0 (ZEEP) exhibited an upward convexity in six patients reflecting a progressive reduction in compliance with inflating volume, whereas PEEP resulted in a volume displacement along the flat part of this curve. After VT reduction, V-P curves in the same patients showed an upward concavity, reflecting progressive alveolar recruitment with inflating volume, and application of PEEP resulted in alveolar recruitment. The other three patients showed a V-P curve with an upward concavity; VT reduction increased this concavity, and application of PEEP induced greater alveolar recruitment than during conventional VT. With PEEP, cardiac index decreased by, respectively, 31% during conventional VT and 11% during low VT (P < 0.01); PaO2 increased by 32% and 71% (P < 0.01), respectively, whereas right-to-left venous admixture (Qs/Qt) decreased by 11% and 40%, respectively (P < 0.01). The greatest values of PaO2, static compliance, and oxygen delivery and the lowest values of Qs/Qt (best PEEP) were obtained during application of PEEP with low VT (P < 0.01).
Although PEEP induced alveolar hyperinflation in most patients during mechanical ventilation with conventional VT, at low VT, there appeared to be a significant alveolar collapse, and PEEP was able to expand these units, improving gas exchange and hemodynamics.
在急性呼吸窘迫综合征（ARDS）患者中，通气方法基于10 - 15 ml/kg的潮气量（VT）和呼气末正压（PEEP）。为避免进一步的肺损伤，有人建议降低VT并允许动脉血二氧化碳分压（PaCO2）升高（允许性高碳酸血症）。在机械通气期间，比较了10 cmH2O的PEEP对采用传统（10 - 15 ml/kg）和低（5 - 8 ml/kg）VT时呼吸力学、血流动力学和气体交换的影响。
对9名接受镇静和肌松的患者进行了研究。VT逐渐降低（每20 - 30分钟降低50 ml）。测量了静态容量 - 压力（V - P）曲线、血流动力学和气体交换。
在采用传统VT进行机械通气期间，6名患者在PEEP为0（零PEEP）时的V - P曲线呈现向上凸，反映随着充气量增加顺应性逐渐降低，而PEEP导致沿着该曲线平坦部分的容量位移。VT降低后，同一患者的V - P曲线显示向上凹，反映随着充气量增加肺泡逐渐复张，并且应用PEEP导致肺泡复张。另外3名患者的V - P曲线呈向上凹；VT降低增加了这种凹陷，并且应用PEEP比传统VT期间诱导了更大程度的肺泡复张。使用PEEP时，心脏指数在传统VT期间分别降低31%，在低VT期间降低11%（P < 0.01）；动脉血氧分压（PaO2）分别升高32%和71%（P < 0.01），而右向左静脉血分流（Qs/Qt）分别降低11%和40%（P < 0.01）。在低VT应用PEEP期间获得了最高的PaO2值、静态顺应性和氧输送以及最低的Qs/Qt值（最佳PEEP）（P < 0.01）。
尽管在采用传统VT进行机械通气期间，大多数患者中PEEP导致肺泡过度充气，但在低VT时，似乎存在明显的肺泡萎陷，并且PEEP能够使这些肺泡单位扩张，改善气体交换和血流动力学。
