Department of Critical Care Medicine, Zhong-Da Hospital, Southeast University School of Medicine, Nanjing, PR China.
Respiration. 2014;87(1):75-83. doi: 10.1159/000354787. Epub 2013 Nov 28.
In the acute respiratory distress syndrome (ARDS), lung-protective ventilation strategies combine the delivery of small tidal volumes (VT) with sufficient positive end-expiratory pressure (PEEP). However, an optimal approach guiding the setting of PEEP has not been defined. Monitoring volumetric capnography is useful to detect changes in lung aeration.
The aim of this study was to determine whether volumetric capnography may be a useful method to determine the optimal PEEP in ARDS.
In 8 lung-lavaged piglets, PEEP was reduced from 20 to 4 cm H2O in steps of 4 cm H2O every 10 min followed by full lung recruitment. Volumetric capnography, respiratory mechanics, blood gas analysis, hemodynamic data and whole-lung computed tomography scans were obtained at each PEEP level.
After lung recruitment, end-expiratory lung volume progressively decreased from 1,160 ± 273 ml at PEEP 20 cm H2O to 314 ± 86 ml at PEEP 4 cm H2O. The ratio of alveolar dead space (VDalv) to alveolar VT (VTalv) and the phase III slope of volumetric capnography (SIII) reached a minimum at PEEP 16 cm H2O. At this PEEP level, overaerated lung regions were significantly reduced, nonaerated lung regions did not increase, and partial pressure of oxygen in arterial blood/fraction of inspired oxygen (P/F) and static respiratory system compliance (Crs) reached a maximum. At PEEP levels <16 cm H2O, nonaerated lung regions significantly increased, P/F and Crs deteriorated, and VDalv/VTalv and SIII began to increase.
In this surfactant-depleted model, PEEP at the lowest VDalv/VTalv and SIII allows an optimal balance between lung overinflation and collapse. Hence, volumetric capnography is a useful bedside approach to identify the optimal PEEP.
在急性呼吸窘迫综合征（ARDS）中，肺保护性通气策略结合小潮气量（VT）和足够的呼气末正压（PEEP）。然而，尚未确定指导 PEEP 设置的最佳方法。监测容量二氧化碳描记术有助于检测肺充气的变化。
本研究旨在确定容量二氧化碳描记术是否可作为确定 ARDS 最佳 PEEP 的有用方法。
在 8 只肺灌洗猪中，PEEP 每 10 分钟从 20 厘米 H2O 降低 4 厘米 H2O，然后进行全肺复张。在每个 PEEP 水平下获得容量二氧化碳描记术、呼吸力学、血气分析、血流动力学数据和全肺计算机断层扫描。
在肺复张后，呼气末肺容积从 PEEP 20 厘米 H2O 的 1160±273 毫升逐渐减少至 PEEP 4 厘米 H2O 的 314±86 毫升。肺泡死腔（VDalv）与肺泡 VT（VTalv）的比值和容量二氧化碳描记术的 III 相斜率在 PEEP 16 厘米 H2O 时达到最小值。在该 PEEP 水平下，过度充气的肺区显著减少，非充气肺区未增加，动脉血氧分压/吸入氧分数（P/F）和静态呼吸系统顺应性（Crs）达到最大值。在 PEEP 水平<16 厘米 H2O 时，非充气肺区显著增加，P/F 和 Crs 恶化，VDalv/VTalv 和 SIII 开始增加。
在这个表面活性剂耗尽的模型中，最低的 VDalv/VTalv 和 SIII 的 PEEP 允许过度充气和塌陷之间达到最佳平衡。因此，容量二氧化碳描记术是一种有用的床边方法，可确定最佳 PEEP。
