Terragni P P, Rosboch G L, Lisi A, Viale A G, Ranieri V M
Università di Torino, Dipartimento di discipline Medico-Chirurgiche, Sezione di Anestesiologia e Rianimazione, Ospedale S. Giovanni Battista, Torino, Italy.
Eur Respir J Suppl. 2003 Aug;42:15s-21s. doi: 10.1183/09031936.03.00420303.
The main supportive therapy in acute respiratory distress syndrome patients is mechanical ventilation. As with any therapy, mechanical ventilation has side-effects, and may induce lung injury (ventilator-induced lung injury (VILI)/ventilator-associated lung injury). The mechanical factors responsible for VILI are thought to be related to tidal recruitment/derecruitment of previously collapsed alveoli and/or pulmonary overdistension. The volume/pressure (V/P) curve of the respiratory system in patients as well as in animal models of acute lung injury (ALI) has a characteristic sigmoid shape, with a lower inflection point (LIP) corresponding to the pressure/end-expiratory volume required to initiate recruitment of collapsed alveoli, and an upper inflection point (UIP) corresponding to the pressure/end inspiratory volume at which alveolar overdistension occurs. "Protective" ventilatory approaches have therefore set out to minimise mechanical injury by using the V/P curve to individualise positive end-expiratory pressure (PEEP) (PEEP above the LIP) and tidal volume (by setting end-inspiratory V/P below the UIP) since a large number of experimental studies correlate P/V curves to histological and biological manifestations of VILI and two randomised trials showed that protective ventilatory strategy individually tailored to the P/V curve minimised pulmonary and systemic inflammation and decreased mortality in patients with ALI. However, despite the fact that several studies have: 1) proposed new techniques to perform pressure/volume curves at the bedside, 2) confirmed that the lower inflection point and upper inflection point correspond to computed tomography scan evidence of atelectasis and overdistension, and 3) demonstrated the ability of the pressure/volume curve to estimate alveolar recruitment with positive end-expiratory pressure, no large studies have assessed whether such measurement can be performed in all intensive care units as a monitoring tool to orient ventilator therapy. Preliminary experimental and clinical studies show that the shape of the dynamic inspiratory pressure/time profile during constant flow inflation (stress index), allows prediction of a ventilatory strategy that minimises the occurrence of ventilator-induced lung injury.
急性呼吸窘迫综合征患者的主要支持性治疗方法是机械通气。与任何治疗方法一样，机械通气也有副作用，可能导致肺损伤（呼吸机诱导的肺损伤/呼吸机相关性肺损伤）。导致呼吸机诱导的肺损伤的机械因素被认为与先前塌陷肺泡的潮气量募集/解募集和/或肺过度扩张有关。急性肺损伤（ALI）患者以及动物模型的呼吸系统的容积/压力（V/P）曲线呈特征性的S形，下拐点（LIP）对应于启动塌陷肺泡募集所需的压力/呼气末容积，上拐点（UIP）对应于发生肺泡过度扩张时的压力/吸气末容积。因此，“保护性”通气方法旨在通过利用V/P曲线个体化呼气末正压（PEEP）（高于LIP的PEEP）和潮气量（通过将吸气末V/P设置低于UIP）来尽量减少机械损伤，因为大量实验研究将P/V曲线与呼吸机诱导的肺损伤的组织学和生物学表现相关联，两项随机试验表明，根据P/V曲线个体化定制的保护性通气策略可将ALI患者的肺部和全身炎症降至最低，并降低死亡率。然而，尽管有几项研究：1）提出了在床边进行压力/容积曲线的新技术，2）证实下拐点和上拐点对应于计算机断层扫描显示的肺不张和过度扩张证据，3）证明压力/容积曲线能够通过呼气末正压估计肺泡募集，但尚无大型研究评估这种测量是否可以在所有重症监护病房作为指导通气治疗的监测工具进行。初步的实验和临床研究表明，在恒流充气过程中动态吸气压力/时间曲线的形状（应力指数），可以预测一种能尽量减少呼吸机诱导的肺损伤发生的通气策略。
