Puybasset L, Gusman P, Muller J C, Cluzel P, Coriat P, Rouby J J
Réanimation Chirurgicale Pierre Viars, Department of Anesthesiology, Hôpital de la Pitié-Salpêtrière, University of Paris Pierre et Marie Curie, France.
Intensive Care Med. 2000 Sep;26(9):1215-27. doi: 10.1007/s001340051340.
To determine whether differences in lung morphology assessed by computed tomography (CT) affect the response to positive end-expiratory pressure (PEEP).
Prospective study over a 53-month period.
Fourteen-bed surgical intensive care unit of a university hospital.
Seventy-one consecutive patients with early adult respiratory distress syndrome (ARDS).
Fast spiral thoracic CT was performed at zero end-expiratory pressure (ZEEP) and after implementation of PEEP 10 cmH2O. Hemodynamic and respiratory parameters were measured in both conditions. PEEP-induced overdistension and alveolar recruitment were quantified by specifically designed software (Lungview). Overdistension occurred only in the upper lobes and was significantly correlated with the volume of lung, characterized by a CT attenuation ranging between -900 and -800 HU in ZEEP conditions. Cardiorespiratory effects of PEEP were similar in patients with primary and secondary ARDS. PEEP-induced alveolar recruitment of the lower lobes was significantly correlated with their lung volume (gas + tissue) at functional residual capacity. PEEP-induced alveolar recruitment was greater in the lower lobes with "inflammatory atelectasis" than in the lower lobes with "mechanical atelectasis." Lung morphology as assessed by CT markedly influenced the effects of PEEP: in patients with diffuse CT attenuations PEEP induced a marked alveolar recruitment without overdistension, whereas in patients with lobar CT attenuations PEEP induced a mild alveolar recruitment associated with overdistension of previously aerated lung areas. These results can be explained by the uneven distribution of regional compliance characterizing patients with lobar CT attenuations (compliant upper lobes and stiff lower lobes) contrasting with a more even distribution of regional compliances observed in patients with diffuse CT attenuations.
In patients with ARDS, the cardiorespiratory effects of PEEP are affected by lung morphology rather than by the cause of the lung injury (primary versus secondary ARDS). The regional distribution of the loss of aeration and the type of atelectasis -- "mechanical" with a massive loss of lung volume, or "inflammatory" with a preservation of lung volume-- characterizing the lower lobes are the main determinants of the cardiorespiratory effects of PEEP.
确定计算机断层扫描（CT）评估的肺部形态差异是否会影响呼气末正压（PEEP）的反应。
为期53个月的前瞻性研究。
大学医院的14张床位的外科重症监护病房。
71例连续性早期成人呼吸窘迫综合征（ARDS）患者。
在呼气末零压力（ZEEP）时以及实施10 cmH2O的PEEP后进行快速螺旋胸部CT检查。在两种情况下均测量血流动力学和呼吸参数。通过专门设计的软件（Lungview）对PEEP引起的过度扩张和肺泡复张进行量化。过度扩张仅发生在上叶，并且与肺体积显著相关，其特征是在ZEEP条件下CT衰减范围在-900至-800 HU之间。原发性和继发性ARDS患者中PEEP的心肺效应相似。PEEP引起的下叶肺泡复张与功能残气量时的肺体积（气体+组织）显著相关。与“机械性肺不张”的下叶相比，“炎性肺不张”的下叶中PEEP引起的肺泡复张更大。CT评估的肺部形态显著影响PEEP的效果：在CT衰减弥漫的患者中，PEEP引起明显的肺泡复张且无过度扩张，而在CT衰减呈叶性的患者中，PEEP引起轻度的肺泡复张并伴有先前通气肺区的过度扩张。这些结果可以通过叶性CT衰减患者（顺应性上叶和僵硬下叶）区域顺应性分布不均来解释，这与弥漫性CT衰减患者中观察到的区域顺应性分布更均匀形成对比。
在ARDS患者中，PEEP的心肺效应受肺部形态影响，而非肺损伤原因（原发性与继发性ARDS）。下叶以肺通气丧失的区域分布和肺不张类型（肺体积大量丧失的“机械性”或肺体积保留的“炎性”）是PEEP心肺效应的主要决定因素。
