Vieillard-Baron Antoine, Prin Sebastien, Schmitt Jean-Marie, Augarde Roch, Page Bernard, Beauchet Alain, Jardin François
Medical Intensive Care Unit, and Department of Biostatistics, University Hospital Ambroise Paré, Assistance Publique Hôpitaux de Paris, Boulogne Cedex, France.
Am J Respir Crit Care Med. 2002 Apr 15;165(8):1107-12. doi: 10.1164/ajrccm.165.8.2106104.
The presence of an initial segment with a low compliance on the static pressure-volume (PV) curve in patients with acute respiratory distress syndrome (ARDS) indicates that some lung compartments do not initially receive insufflated gas. We tested the hypothesis that an uneven distribution of time constants, producing a "slow compartment," was in part responsible for the change in compliance between the initial and the intermediate segment of the PV curve. In 16 patients with ARDS submitted to mechanical ventilation in volume-controlled mode with a supportive respiratory rate of 15 breaths/minute, we constructed the static PV curve on the first day of respiratory support and determined the intrinsic positive end-expiratory pressure (PEEPi4) during a prolonged end-expiratory pause (4 seconds). We also measured the volume of a "slow compartment" during a prolonged expiration (> 6 seconds), and determined an external PEEP (PEEPe) suppressing PEEPi4. Among the 16 patients studied, 11 exhibited a low inflection point, associated with a "slow compartment" of 172 +/- 83 ml, responsible for a PEEPi4 of 3 +/- 2 cm H2O. Conversely, the five remaining patients had a linear PV curve, associated with a minimal "slow compartment" of 28 +/- 10 ml, responsible for a negligible PEEPi4. We observed that individual slopes of the initial segment of the PV curve were inversely and significantly correlated with the proportion of the "slow compartment" (r = -0.85). We concluded that the shape of the inspiratory PV curve in ARDS might be dependent on the presence of a "slow compartment," and demonstrated that a low external PEEP appeared sufficient to achieve a substantial mechanical improvement in clinical practice.
急性呼吸窘迫综合征（ARDS）患者的静态压力-容积（PV）曲线上存在初始段顺应性较低的情况，这表明一些肺区最初并未接受吹入的气体。我们检验了以下假设：时间常数分布不均产生“慢肺区”，这在一定程度上导致了PV曲线初始段与中间段之间顺应性的变化。在16例接受容量控制模式机械通气、支持呼吸频率为15次/分钟的ARDS患者中，我们在呼吸支持的第一天构建了静态PV曲线，并在延长的呼气末暂停（4秒）期间测定了内在呼气末正压（PEEPi4）。我们还在延长呼气（>6秒）期间测量了“慢肺区”的容积，并确定了抑制PEEPi4的外部呼气末正压（PEEPe）。在研究的16例患者中，11例表现出低拐点，伴有172±83 ml的“慢肺区”，其导致的PEEPi4为3±2 cm H2O。相反，其余5例患者的PV曲线呈线性，伴有最小为28±10 ml的“慢肺区”，其导致的PEEPi4可忽略不计。我们观察到PV曲线初始段的个体斜率与“慢肺区”的比例呈显著负相关（r = -0.85）。我们得出结论，ARDS患者吸气PV曲线的形状可能取决于“慢肺区”的存在，并证明在临床实践中，低水平的外部呼气末正压似乎足以实现显著的机械改善。
