Pelosi P, Crotti S, Brazzi L, Gattinoni L
Istituto di Anestesia e Rianimazione, Università di Milano, Ospedale Maggiore IRCCS, Italy.
Eur Respir J. 1996 May;9(5):1055-62. doi: 10.1183/09031936.96.09051055.
Computed tomography (CT) has played an important role in improving our knowledge of the pathophysiology of the adult respiratory distress syndrome (ARDS), and in determining the morphological and functional relationships of different manoeuvres commonly used in the therapeutic management of this syndrome (changes in body position, application of positive end-expiratory pressure (PEEP) and mechanical ventilation). During the early phase of the disease, the ARDS lung is characterized by a homogenous alteration of the vascular permeability. Thus, oedema accumulates evenly in all lung regions with a nongravitational distribution (homogenous lung). The increased lung weight, due to increased oedema, causes a collapse of the lung regions along the vertical axis, through the transmission of hydrostatic forces (compression atelectasis). Thus, the lesions appear mainly in the dependent lung regions (dishomogeneous lung). During inspiration, at plateau pressure, the pulmonary units reopen and, if the PEEP applied is adequate, they stay open during the following expiration. Adequate PEEP is equal to or higher than the hydrostatic forces compressing that unit. Prone position is another manoeuvre which allows previously collapsed lung regions to reopen and, conversely, compresses previously aerated regions, reversing the distribution of gravitational forces. During late ARDS, there is less compression atelectasis and the lung undergoes structural changes, due to the reduced amount of oedema. This is usually associated with CO2 retention and the development of emphysema-like lesions. In conclusion, computed tomography is not only a research tool, but a useful technique which allows a better understanding of the progressive change in strategy needed to ventilate the adult respiratory distress syndrome lung at different stages of the disease.
计算机断层扫描（CT）在增进我们对成人呼吸窘迫综合征（ARDS）病理生理学的认识方面发挥了重要作用，并且有助于确定该综合征治疗管理中常用的不同操作（体位改变、呼气末正压通气（PEEP）的应用和机械通气）之间的形态学和功能关系。在疾病的早期阶段，ARDS肺的特征是血管通透性均匀改变。因此，水肿在所有肺区域均匀积聚，呈非重力分布（均匀肺）。由于水肿增加导致肺重量增加，通过静水压力的传递（压迫性肺不张），沿垂直轴的肺区域会发生塌陷。因此，病变主要出现在下垂肺区域（不均匀肺）。在吸气时，在平台压下，肺单位重新开放，如果应用的PEEP足够，它们在接下来的呼气过程中会保持开放。足够的PEEP等于或高于压迫该单位的静水压力。俯卧位是另一种操作，它能使先前塌陷的肺区域重新开放，反之，压迫先前通气的区域，从而逆转重力的分布。在ARDS晚期，由于水肿量减少，压迫性肺不张减少，肺会发生结构变化。这通常与二氧化碳潴留和类肺气肿样病变的发展有关。总之，计算机断层扫描不仅是一种研究工具，而且是一项有用的技术，它能让我们更好地理解在疾病的不同阶段对ARDS肺进行通气所需策略的逐步变化。
