Unidad de Pacientes Críticos, Departamento de Medicina, Hospital Clínico Universidad de Chile, Santiago, Chile.
Am J Respir Crit Care Med. 2013 Aug 15;188(4):440-8. doi: 10.1164/rccm.201207-1279OC.
Positive end-expiratory pressure (PEEP) and prone positioning may induce lung recruitment and affect alveolar dynamics in acute respiratory distress syndrome (ARDS). Whether there is interdependence between the effects of PEEP and prone positioning on these variables is unknown.
To determine the effects of high PEEP and prone positioning on lung recruitment, cyclic recruitment/derecruitment, and tidal hyperinflation and how these effects are influenced by lung recruitability.
Mechanically ventilated patients (Vt 6 ml/kg ideal body weight) underwent whole-lung computed tomography (CT) during breath-holding sessions at airway pressures of 5, 15, and 45 cm H2O and Cine-CTs on a fixed thoracic transverse slice at PEEP 5 and 15 cm H2O. CT images were repeated in supine and prone positioning. A recruitment maneuver at 45 cm H2O was performed before each PEEP change. Lung recruitability was defined as the difference in percentage of nonaerated tissue between 5 and 45 cm H2O. Cyclic recruitment/de-recruitment and tidal hyperinflation were determined as tidal changes in percentage of nonaerated and hyperinflated tissue, respectively.
Twenty-four patients with ARDS were included. Increasing PEEP from 5 to 15 cm H2O decreased nonaerated tissue (501 ± 201 to 322 ± 132 grams; P < 0.001) and increased tidal-hyperinflation (0.41 ± 0.26 to 0.57 ± 0.30%; P = 0.004) in supine. Prone positioning further decreased nonaerated tissue (322 ± 132 to 290 ± 141 grams; P = 0.028) and reduced tidal hyperinflation observed at PEEP 15 in supine patients (0.57 ± 0.30 to 0.41 ± 0.22%). Cyclic recruitment/de-recruitment only decreased when high PEEP and prone positioning were applied together (4.1 ± 1.9 to 2.9 ± 0.9%; P = 0.003), particularly in patients with high lung recruitability.
Prone positioning enhances lung recruitment and decreases alveolar instability and hyperinflation observed at high PEEP in patients with ARDS.
呼气末正压（PEEP）和俯卧位可能会诱发急性呼吸窘迫综合征（ARDS）患者的肺复张，并影响肺泡动态。但目前尚不清楚 PEEP 和俯卧位对这些变量的影响是否存在相互依赖性。
确定高 PEEP 和俯卧位对肺复张、周期性复张/去复张以及潮气量过度充气的影响，以及这些影响如何受到肺可复张性的影响。
在机械通气患者（VT 为理想体重的 6ml/kg）进行屏气时，使用全肺 CT（在气道压力为 5、15 和 45cmH2O 时）和 Cine-CT（在 PEEP 为 5 和 15cmH2O 时在固定的胸横向切片上）进行检测。在仰卧位和俯卧位时重复 CT 图像。在每次 PEEP 变化前进行 45cmH2O 的复张操作。肺可复张性定义为 5cmH2O 和 45cmH2O 之间非充气组织的百分比差异。周期性复张/去复张和潮气量过度充气分别定义为潮气量时非充气和过度充气组织的百分比变化。
共纳入 24 例 ARDS 患者。与仰卧位时相比，将 PEEP 从 5cmH2O 增加到 15cmH2O 可减少非充气组织（501 ± 201 克至 322 ± 132 克；P < 0.001）并增加潮气量过度充气（0.41 ± 0.26 至 0.57 ± 0.30%；P = 0.004）。俯卧位进一步减少非充气组织（322 ± 132 克至 290 ± 141 克；P = 0.028），并降低仰卧位时 PEEP 为 15cmH2O 时观察到的潮气量过度充气（0.57 ± 0.30 至 0.41 ± 0.22%）。仅当应用高 PEEP 和俯卧位时，周期性复张/去复张才会减少（4.1 ± 1.9 至 2.9 ± 0.9%；P = 0.003），特别是在肺可复张性高的患者中。
俯卧位可增强 ARDS 患者的肺复张，并降低高 PEEP 时观察到的肺泡不稳定和过度充气。
