Bersten A D
Dept of Critical Care Medicine, Flinders Medical Centre, Adelaide, SA, Australia.
Eur Respir J. 1998 Sep;12(3):526-32. doi: 10.1183/09031936.98.12030526.
Strategies to optimize alveolar recruitment and prevent lung overinflation are central to ventilatory management of patients with acute lung injury (ALI). The recent description of overinflation using multilinear regression analysis of airway pressure (Paw) and flow (V') data allows a functional assessment of lung mechanics. However, this technique has not been studied in ALI patients. During 15 positive end-expiratory pressure (PEEP) trials in 10 ALI patients, respiratory elastance was partitioned into volume-independent (E1) and volume-dependent (E2VT) components, where Paw=(E1+E2VT)V+RrsV'+Po; where V is volume, VT is tidal volume, Rrs is respiratory resistance and Po is static recoil pressure at end-expiration (equivalent to total PEEP). Then, %E2 was calculated as (100E2VT)/(E1+E2VT); a measure of lung overinflation when %E2>30%. Alveolar recruitment, assessed as a PEEP-induced increase in V>50 mL at a constant Paw occurred in 14 of 15 trials (299+/-34 mL, mean+/-SEM), but was independent of the degree of lung inflation. Lung overinflation was common (six of 15 clinically set PEEP levels) and occurred despite a dynamic elastic distending pressure (Pel,dyn) <30 cmH2O during 18 of 36 PEEP titrations. During a PEEP titration the resultant %E2 was directly related to delta(peak airway pressure-Po) (rs=0.86, p<0.001) and delta(Pel,dyn-Po) (rs=0.89, p<0.001). The 95% predictive intervals for a 2 cmH2O change in either driving pressure were %E2 values of 30.4-68.1% and 32.8-69.2%, respectively. Single or continuous measurement of %E2 (a measure of lung inflation) is a readily available method for titrating ventilatory parameters. Further, during a positive end-expiratory pressure titration a change in ventilatory driving pressure > or =2 cmH2O is indicative of overinflation.
优化肺泡复张并防止肺过度膨胀的策略是急性肺损伤（ALI）患者通气管理的核心。最近通过对气道压力（Paw）和流量（V'）数据进行多线性回归分析来描述过度膨胀，这使得对肺力学进行功能评估成为可能。然而，该技术尚未在ALI患者中进行研究。在对10例ALI患者进行的15次呼气末正压（PEEP）试验中，呼吸弹性被分为与容积无关（E1）和与容积有关（E2VT）的成分，其中Paw =（E1 + E2VT）V + RrsV'+ Po；其中V是容积，VT是潮气量，Rrs是呼吸阻力，Po是呼气末的静态回缩压力（相当于总PEEP）。然后，计算%E2为（100E2VT）/（E1 + E2VT）；当%E2> 30%时作为肺过度膨胀的指标。在15次试验中的14次试验中出现了肺泡复张，即在恒定Paw下PEEP诱导的V增加> 50 mL（299±34 mL，平均值±标准误），但与肺膨胀程度无关。肺过度膨胀很常见（15个临床设定的PEEP水平中有6个），并且在36次PEEP滴定中的18次滴定期间尽管动态弹性扩张压力（Pel，dyn）<30 cmH2O仍会发生。在PEEP滴定期间，所得的%E2与δ（峰值气道压力 - Po）直接相关（rs = 0.86，p <0.001）和δ（Pel，dyn - Po）（rs = 0.89，p <0.001）。两种驱动压力变化2 cmH2O时的95%预测区间分别为%E2值30.4 - 68.1%和32.8 - 69.2%。单次或连续测量%E2（一种肺膨胀指标）是滴定通气参数的一种现成方法。此外，在呼气末正压滴定期间，通气驱动压力变化≥2 cmH2O表明存在过度膨胀。
