Gilbert T B, Barnas G M, Sequeira A J
Department of Anesthesiology, University of Maryland Medical System, Baltimore, USA.
J Cardiothorac Vasc Anesth. 1996 Dec;10(7):844-9. doi: 10.1016/s1053-0770(96)80043-7.
To determine effects of surgical pleurotomy, continuous positive airway pressure, and fluid balance during cardiopulmonary bypass (CPB) on lung mechanical properties and indices of oxygenation.
Prospective, descriptive, and interventional study.
Cardiothoracic service at a major university referral center.
Eighteen anesthetized-paralyzed patients undergoing elective coronary artery bypass grafting requiring CPB.
During CPB, continuous positive airway pressure (CPAP) was applied to nine patients, in nine others, no CPAP was applied.
From measurements of airway and esophageal pressures and flow, lung resistance and elastance were determined before sternotomy and after sternal reapproximation. Measurements were made during forced ventilation over a physiologic range of tidal volumes and frequencies, and frequency and volume dependences of lung resistance and elastance were additionally identified. In all patients, lung resistance and elastance increased after CPB, consistent with models of pulmonary edema. Multiple regression analysis showed that these increases were relatively less in patients with intact pleurae (p < 0.05) or net negative fluid balance (p < 0.05); however, no difference in these increases was noted between patients receiving CPAP and those receiving no CPAP. Increases in lung resistance were positively correlated to net fluid balance, and negatively correlated to frequency and tidal volume (p < 0.05). Increases in lung elastance were positively correlated to tidal volume (p < 0.05). Absolute change in alveolar-arterial oxygen gradient was negatively correlated with net fluid balance, whereas percentage change was positively correlated to changes in lung elastance (p < 0.05).
These findings suggest that pleurotomy before CPB and positive fluid balance during CPB enhance postbypass pulmonary edema and/or atelectasis, as demonstrated by acute changes in respiratory mechanics and indices of oxygenation. Low levels of CPAP applied during CPB did not significantly change either mechanical properties or oxygenation.
确定手术胸膜切开术、持续气道正压通气以及体外循环（CPB）期间的液体平衡对肺机械性能和氧合指标的影响。
前瞻性、描述性和干预性研究。
一所主要大学转诊中心的心胸外科。
18例接受择期冠状动脉搭桥术且需要CPB的麻醉瘫痪患者。
在CPB期间，对9例患者应用持续气道正压通气（CPAP），另外9例患者未应用CPAP。
通过气道和食管压力及流量测量，在胸骨切开术前和胸骨重新对合后测定肺阻力和弹性。在生理潮气量和频率范围内进行强制通气时进行测量，并额外确定肺阻力和弹性的频率和容量依赖性。所有患者在CPB后肺阻力和弹性均增加，这与肺水肿模型一致。多元回归分析表明，在胸膜完整（p<0.05）或净液体平衡为负（p<0.05）的患者中，这些增加相对较小；然而，接受CPAP的患者和未接受CPAP的患者在这些增加方面没有差异。肺阻力增加与净液体平衡呈正相关，与频率和潮气量呈负相关（p<0.05）。肺弹性增加与潮气量呈正相关（p<0.05）。肺泡-动脉氧梯度的绝对变化与净液体平衡呈负相关，而百分比变化与肺弹性变化呈正相关（p<0.05）。
这些发现表明，CPB前的胸膜切开术和CPB期间的正液体平衡会加重体外循环后的肺水肿和/或肺不张，这在呼吸力学和氧合指标的急性变化中得到了证实。CPB期间应用的低水平CPAP并未显著改变机械性能或氧合。
