Muellenbach Ralf M, Kredel Markus, Zollhoefer Bernd, Wunder Christian, Roewer Norbert, Brederlau Joerg
Department of Anaesthesiology, University of Wuerzburg Oberduerrbacher Strasse 6, 97080 Wuerzburg, Germany.
BMC Anesthesiol. 2006 Jun 22;6:8. doi: 10.1186/1471-2253-6-8.
To compare the effect of a sustained inflation followed by an incremental mean airway pressure trial during conventional and high-frequency oscillatory ventilation on oxygenation and hemodynamics in a large porcine model of early acute respiratory distress syndrome.
Severe lung injury (Ali) was induced in 18 healthy pigs (55.3 +/- 3.9 kg, mean +/- SD) by repeated saline lung lavage until PaO2 decreased to less than 60 mmHg. After a stabilisation period of 60 minutes, the animals were randomly assigned to two groups: Group 1 (Pressure controlled ventilation; PCV): FIO2 = 1.0, PEEP = 5 cmH2O, V(T) = 6 ml/kg, respiratory rate = 30/min, I:E = 1:1; group 2 (High-frequency oscillatory ventilation; HFOV): FIO2 = 1.0, Bias flow = 30 l/min, Amplitude = 60 cmH2O, Frequency = 6 Hz, I:E = 1:1. A sustained inflation (SI; 50 cmH2O for 60s) followed by an incremental mean airway pressure (mPaw) trial (steps of 3 cmH2O every 15 minutes) were performed in both groups until PaO2 no longer increased. This was regarded as full lung inflation. The mPaw was decreased by 3 cmH2O and the animals reached the end of the study protocol. Gas exchange and hemodynamic data were collected at each step.
The SI led to a significant improvement of the PaO2/FiO2-Index (HFOV: 200 +/- 100 vs. PCV: 58 +/- 15 and T(Ali): 57 +/- 12; p < 0.001) and PaCO2-reduction (HFOV: 42 +/- 5 vs. PCV: 62 +/- 13 and T(Ali): 55 +/- 9; p < 0.001) during HFOV compared to lung injury and PCV. Augmentation of mPaw improved gas exchange and pulmonary shunt fraction in both groups, but at a significant lower mPaw in the HFOV treated animals. Cardiac output was continuously deteriorating during the recruitment manoeuvre in both study groups (HFOV: T(Ali): 6.1 +/- 1 vs. T(75): 3.4 +/- 0.4; PCV: T(Ali): 6.7 +/- 2.4 vs. T(75): 4 +/- 0.5; p < 0.001).
A sustained inflation followed by an incremental mean airway pressure trial in HFOV improved oxygenation at a lower mPaw than during conventional lung protective ventilation. HFOV but not PCV resulted in normocapnia, suggesting that during HFOV there are alternatives to tidal ventilation to achieve CO2-elimination in an "open lung" approach.
在大型猪早期急性呼吸窘迫综合征模型中，比较传统通气和高频振荡通气时持续膨胀后进行气道平均压递增试验对氧合和血流动力学的影响。
通过反复生理盐水肺灌洗诱导18只健康猪（55.3±3.9kg，平均±标准差）发生严重肺损伤（ALI），直至动脉血氧分压（PaO2）降至60mmHg以下。在60分钟的稳定期后，将动物随机分为两组：第1组（压力控制通气；PCV）：吸入氧分数（FIO2）=1.0，呼气末正压（PEEP）=5cmH2O，潮气量（V(T)）=6ml/kg，呼吸频率=30次/分钟，吸呼比（I:E）=1:1；第2组（高频振荡通气；HFOV）：FIO2=1.0，偏流=30L/分钟，振幅=60cmH2O，频率=6Hz，I:E=1:1。两组均先进行持续膨胀（SI；50cmH2O持续60秒），然后进行气道平均压（mPaw）递增试验（每15分钟增加3cmH2O），直至PaO2不再升高，此时视为肺完全膨胀。mPaw降低3cmH2O，动物达到研究方案终点。在每个步骤收集气体交换和血流动力学数据。
与肺损伤和PCV相比，HFOV期间SI导致PaO2/FiO2指数显著改善（HFOV：200±100 vs.PCV：58±15以及肺损伤时：57±12；p<0.001）和PaCO2降低（HFOV：42±5 vs.PCV：62±13以及肺损伤时：55±9；p<0.001）。mPaw增加改善了两组的气体交换和肺分流分数，但HFOV治疗的动物在显著更低的mPaw时即有改善。在两个研究组的肺复张操作过程中的心输出量持续恶化（HFOV：肺损伤时：6.1±1 vs.75cmH2O时：3.4±0.4；PCV：肺损伤时：6.7±2.4 vs.75cmH2O时：4±0.5；p<0.001）。
HFOV中持续膨胀后进行气道平均压递增试验在比传统肺保护性通气更低的mPaw时改善了氧合。HFOV而非PCV导致正常碳酸血症，提示在HFOV期间，有替代潮气量通气的方法以“开放肺”策略实现二氧化碳清除。
