Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, Pennsylvania.
Intensive Care Unit, Alfred Hospital, Melbourne, Victoria, Australia.
Ann Am Thorac Soc. 2021 May;18(5):857-864. doi: 10.1513/AnnalsATS.202007-862OC.
Clinicians commonly use short-term physiologic markers to assess the benefit of ventilator adjustments. Improved arterial oxygen tension/pressure (Pa)/fraction of inspired oxygen (Fi) after ventilator adjustment in acute respiratory distress syndrome is associated with lower mortality. However, as driving pressure (ΔP) reflects lung stress and strain, changes in ΔP may more accurately reflect benefits or harms of ventilator adjustments compared with changes in oxygenation. We aimed to compare the association between mortality and the changes in Pa/Fi and ΔP following protocolized ventilator changes. We assessed associations between mortality and changes in Pa/Fi (ΔPa/Fi) and ΔP (ΔΔP) after postrandomization positive end-expiratory pressure (PEEP) and tidal volume adjustment in reanalyses of the ALVEOLI (Assessment of Low Tidal Volume and Elevated End-Expiratory Volume to Obviate Lung Injury) and ExPress (Expiratory Pressure) trials. We included subjects with available pre- and postintervention Pa/Fi and ΔP (372 in ALVEOLI and 596 in ExPress). In each separate trial cohort, we performed multivariable Cox regression testing the association between ΔPa/Fi and ΔΔP with mortality. In ALVEOLI, when analyzed as separate variables, ΔPa/Fi was associated with mortality only in subjects in whom PEEP increased, whereas ΔΔP was associated with mortality irrespective of direction of PEEP change. When modeled together, improved ΔPa/Fi was not associated with mortality, whereas ΔΔP remained associated with mortality (adjusted hazard ratio [aHR], 1.50 per 5 cm HO increase; 95% confidence interval [95% CI], 1.21-1.85). When modeled together in ExPress, ΔΔP (aHR, 1.42; 95% CI, 1.14-1.78) was more strongly associated with mortality than ΔPa/Fi (aHR, 0.95 per 25 mm Hg increase; 95% CI, 0.90-1.00). Reduced ΔP following protocolized ventilator changes was more strongly and consistently associated with lower mortality than was increased Pa/Fi, making ΔΔP more informative about benefit from ventilator adjustments. Our results reinforce the primacy of ΔP, rather than oxygenation, as the key variable associated with outcome.
临床医生通常使用短期生理标志物来评估呼吸机调整的效果。急性呼吸窘迫综合征患者在呼吸机调整后动脉血氧分压/压力（Pa）/吸入氧分数（Fi）改善与死亡率降低相关。然而，由于驱动压（ΔP）反映了肺的应激和应变，与氧合变化相比，ΔP 的变化可能更准确地反映呼吸机调整的益处或危害。我们旨在比较程序性呼吸机改变后 Pa/Fi 和 ΔP 变化与死亡率之间的关联。我们评估了 Reanalyses of the ALVEOLI（Assessment of Low Tidal Volume and Elevated End-Expiratory Volume to Obviate Lung Injury）和 ExPress（Expiratory Pressure）试验中随机化后呼气末正压（PEEP）和潮气量调整后死亡率与 Pa/Fi（ΔPa/Fi）和ΔP（ΔΔP）变化之间的关联。我们纳入了有预干预和干预后 Pa/Fi 和 ΔP 数据的受试者（ALVEOLI 中 372 例，ExPress 中 596 例）。在每个单独的试验队列中，我们使用多变量 Cox 回归检验了ΔPa/Fi 和 ΔΔP 与死亡率之间的关联。在 ALVEOLI 中，当作为单独变量进行分析时，仅在 PEEP 增加的患者中ΔPa/Fi 与死亡率相关，而 ΔΔP 与死亡率相关，与 PEEP 变化方向无关。当一起建模时，改善的ΔPa/Fi 与死亡率无关，而ΔΔP 仍与死亡率相关（调整后的危险比[aHR]，每增加 5 cm H2O 增加 1.50；95%置信区间[95%CI]，1.21-1.85）。当在 ExPress 中一起建模时，ΔΔP（aHR，1.42；95%CI，1.14-1.78）与死亡率的相关性强于ΔPa/Fi（aHR，每增加 25mmHg 增加 0.95；95%CI，0.90-1.00）。与增加 Pa/Fi 相比，程序性呼吸机改变后 ΔP 的降低与死亡率降低的相关性更强且更一致，这表明ΔΔP 更能反映呼吸机调整的益处。我们的结果强调了 ΔP 而不是氧合作用作为与结局相关的关键变量的首要地位。
