急性呼吸窘迫综合征高PEEP应用的利与弊

The advantages and disadvantages of applying high positive end-expiratory pressure in acute respiratory distress syndrome

急性呼吸窘迫综合征(ARDS)的主要病理生理特点是肺泡炎性水肿、塌陷和通气血流比失调。儿童急性肺损伤会议共识推荐仍以肺保护通气策略作为儿童ARDS机械通气的首选。提出小潮气量,严密监测情况下高呼气末正压(positive end-expiratory pressure,PEEP)来改善氧合。高PEEP是"肺开放策略"的重要技术手段,通过肺复张的操作和肺泡开放的维持,有利于改善氧合。高PEEP在动物实验模型中减少了肺水肿的形成。大型成人随机对照试验显示高PEEP可以减少严重低氧血症患者病死率,但该观点最近受到了一些挑战。于此同时,高PEEP和肺组织过度膨胀导致的呼吸机相关性肺损伤密切相关,并增加气压伤和气胸的发生率。高PEEP可减少回心血量,降低心输出量,也可降低脑灌注压,加重脑水肿。目前利用高PEEP来优化ARDS患者的肺复张、选择最佳PEEP维持肺泡的合理开放仍然是一个极具争议的问题。有人提出肺复张的目的不再是恢复正常的肺通气,而是首先提供合理动脉氧饱和度,并减少氧毒性效应。如果肺萎陷是弥漫性的,可合理地应用高于10 cmH2O的PEEP水平来优化肺复张。当肺萎陷呈局部分布时,则不适合使用过高PEEP进行复张,而可以采用其他方法改善通气血流比。

The main pathophysiological features of acute respiratory distress syndrome (ARDS) are alveolitis edema, collapse and V/Q ratio imbalance.Consensus Recommendations from the Pediatric Acute Lung Injury Consensus Conference recommends that the lung protective ventilation strategy be the first choice for mechanical ventilation of PARDS with small tidal volume and high positive end-expiratory pressure(PEEP) used to improve oxygenation.High PEEP is an important technical tool for the "Open Lung Concept". It is beneficial to improve oxygenation through the operation of lung recruitment (RM) and the maintenance of alveolar open.High PEEP reduced the formation of pulmonary edema in animal experimental models.Large-scale adult randomized controlled trials have shown that high PEEP may reduce mortality in patients with severe hypoxemia, but it is currently subject to some challenges.Simultaneously, high PEEP and ventilator-induced lung injury(VILI) caused by excessive lung expansion are closely related, and increase the incidence of barotrauma and pneumothorax.High PEEP may reduce the volume of blood returning to the heart, reduce cardiac output, and also reduce cerebral perfusion pressure and aggravate brain edema.It is still a highly controversial issue to use high PEEP to optimize lung recruitment in patients with ARDS and to choose the best PEEP to maintain the alveolar open.It has been suggested that the purpose of lung recruitment is no longer to restore normal lung ventilation, but to provide reasonable arterial oxygen saturation and reduce oxygen toxicity priority.PEEP above 10 cmH2O is suggested to be used to optimize lung recruitment if lung collapse is diffuse.When the lung collapse is locally distributed, it is not suitable to use excessive PEEP for RM and other methods can be used to improve V/Q ratio.