Rouby J J, Lu Q, Vieira S
Réanimation Chirurgicale Pierre Viars, Dept of Anesthesiology, Hospital Pitié-Salpétrière, University Paris VI, Paris, France.
Eur Respir J Suppl. 2003 Aug;42:27s-36s. doi: 10.1183/09031936.03.00420503.
Pressure/volume (P/V) curves can be measured by static methods, constant or sinusoidal flow methods and the dynostatic method that allows a breath-to-breath determination of P/V curves. Recent ventilators are equipped with specific flow generators and software aimed at obtaining P/V curves without disconnecting the patient from the ventilator. The most recent generation of computed tomography scanners allows the quantitative determination of lung aeration, lung volumes (gas and tissue), alveolar recruitment and lung overinflation of the whole lung. In the supine position, the acute respiratory distress syndrome (ARDS) lung is characterised by an increase in lung tissue that predominates in upper lobes and a massive loss of aeration that predominates in lower lobes. In a minority of ARDS patients, the loss of aeration is homogeneously distributed. The overall lung volume of upper lobes is preserved suggesting an alveolar flooding-induced loss of aeration. In contrast, the overall lung volume of lower lobes is reduced because the heart and the abdomen exert an external compression that contributes to the loss of aeration. The P/V curve is a lung recruitment curve and the chord compliance indicates the potential for recruitment. In such patients, alveolar recruitment resulting from positive end-expiratory pressure is not accompanied by lung overinflation. In a majority of acute respiratory distress syndrome patients, upper lobes remain partially or totally aerated despite a marked regional increase in lung tissue. The upper lobes' overall lung volume is either normal or increased, suggesting that the lung does not collapse under its own weight as generally believed. In lower lobes, the overall lung volume is reduced because the heart and the abdomen exert an external compression that contributes to the loss of aeration. The pressure/volume curve is influenced by the recruitment of poorly and nonaerated lung regions and by the mechanical properties of the part of the lung remaining aerated. In such patients, alveolar recruitment resulting from positive end-expiratory pressure >10 cmH2O is preceded and accompanied by lung overinflation.
压力/容积（P/V）曲线可通过静态方法、恒定或正弦流方法以及允许逐次呼吸测定P/V曲线的动态静态方法来测量。最新的呼吸机配备了特定的流量发生器和软件，旨在在不将患者与呼吸机断开连接的情况下获得P/V曲线。最新一代的计算机断层扫描扫描仪能够对全肺的肺通气、肺容积（气体和组织）、肺泡复张和肺过度充气进行定量测定。在仰卧位时，急性呼吸窘迫综合征（ARDS）肺的特征是肺组织增加以上叶为主，以及通气大量丧失以下叶为主。在少数ARDS患者中，通气丧失呈均匀分布。上叶的总体肺容积得以保留，提示肺泡灌洗导致通气丧失。相比之下，下叶的总体肺容积减少，因为心脏和腹部施加的外部压迫导致了通气丧失。P/V曲线是一条肺复张曲线，弦顺应性表明复张的潜力。在这类患者中，呼气末正压导致的肺泡复张不会伴有肺过度充气。在大多数急性呼吸窘迫综合征患者中，尽管肺组织有明显的局部增加，但上叶仍部分或完全通气。上叶的总体肺容积正常或增加，这表明肺不会像通常认为的那样因自身重量而塌陷。在下叶，总体肺容积减少，因为心脏和腹部施加的外部压迫导致了通气丧失。压力/容积曲线受未通气和非通气肺区域的复张以及剩余通气肺部分的力学特性影响。在这类患者中，呼气末正压>10 cmH₂O导致的肺泡复张之前并伴有肺过度充气。
