Pulmonary Engineering Group, Department of Anaesthesiology and Intensive Care Therapy, University Hospital Carl Gustav Carus, Technical University of Dresden, Fetscherstr, Dresden, Germany.
Crit Care. 2010;14(2):R34. doi: 10.1186/cc8912. Epub 2010 Mar 16.
There is an increasing interest in biphasic positive airway pressure with spontaneous breathing (BIPAP+SBmean), which is a combination of time-cycled controlled breaths at two levels of continuous positive airway pressure (BIPAP+SBcontrolled) and non-assisted spontaneous breathing (BIPAP+SBspont), in the early phase of acute lung injury (ALI). However, pressure support ventilation (PSV) remains the most commonly used mode of assisted ventilation. To date, the effects of BIPAP+SBmean and PSV on regional lung aeration and ventilation during ALI are only poorly defined.
In 10 anesthetized juvenile pigs, ALI was induced by surfactant depletion. BIPAP+SBmean and PSV were performed in a random sequence (1 h each) at comparable mean airway pressures and minute volumes. Gas exchange, hemodynamics, and inspiratory effort were determined and dynamic computed tomography scans obtained. Aeration and ventilation were calculated in four zones along the ventral-dorsal axis at lung apex, hilum and base.
Compared to PSV, BIPAP+SBmean resulted in: 1) lower mean tidal volume, comparable oxygenation and hemodynamics, and increased PaCO2 and inspiratory effort; 2) less nonaerated areas at end-expiration; 3) decreased tidal hyperaeration and re-aeration; 4) similar distributions of ventilation. During BIPAP+SBmean: i) BIPAP+SBspont had lower tidal volumes and higher rates than BIPAP+SBcontrolled; ii) BIPAP+SBspont and BIPAP+SBcontrolled had similar distributions of ventilation and aeration; iii) BIPAP+SBcontrolled resulted in increased tidal re-aeration and hyperareation, compared to PSV. BIPAP+SBspont showed an opposite pattern.
In this model of ALI, the reduction of tidal re-aeration and hyperaeration during BIPAP+SBmean compared to PSV is not due to decreased nonaerated areas at end-expiration or different distribution of ventilation, but to lower tidal volumes during BIPAP+SBspont. The ratio between spontaneous to controlled breaths seems to play a pivotal role in reducing tidal re-aeration and hyperaeration during BIPAP+SBmean.
在急性肺损伤（ALI）的早期阶段，人们对具有自主呼吸的双相正压通气（BIPAP+SBmean）越来越感兴趣，它是两种水平的持续气道正压通气（BIPAP+SBcontrolled）和非辅助自主呼吸（BIPAP+SBspont）的组合。然而，压力支持通气（PSV）仍然是最常用的辅助通气模式。迄今为止，BIPAP+SBmean 和 PSV 对 ALI 期间区域性肺充气和通气的影响仅定义不佳。
在 10 只麻醉的幼年猪中，通过表面活性剂耗竭诱导 ALI。以随机顺序（各 1 小时）进行 BIPAP+SBmean 和 PSV，比较平均气道压力和分钟通气量。确定气体交换、血流动力学和吸气努力，并进行动态计算机断层扫描。在肺尖、肺门和肺底沿腹背轴的四个区域计算充气和通气。
与 PSV 相比，BIPAP+SBmean 导致：1）更低的平均潮气量，相似的氧合和血流动力学，以及更高的 PaCO2 和吸气努力；2）呼气末非充气区域减少；3）减少潮气量过度充气和再充气；4）相似的通气分布。在 BIPAP+SBmean 期间：i）BIPAP+SBspont 的潮气量和速率低于 BIPAP+SBcontrolled；ii）BIPAP+SBspont 和 BIPAP+SBcontrolled 的通气和充气分布相似；iii）与 PSV 相比，BIPAP+SBcontrolled 导致潮气量再充气和过度充气增加。BIPAP+SBspont 则表现出相反的模式。
在这种 ALI 模型中，与 PSV 相比，BIPAP+SBmean 期间潮气量再充气和过度充气减少并不是由于呼气末非充气区域减少或通气分布不同，而是由于 BIPAP+SBspont 的潮气量减少。自主呼吸与控制呼吸的比例似乎在减少 BIPAP+SBmean 期间的潮气量再充气和过度充气方面起着关键作用。
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