Therapeutic hypercapnia and ventilation-perfusion matching in acute lung injury: low minute ventilation vs inspired CO2.
Therapeutic hypercapnia and ventilation-perfusion matching in acute lung injury: low minute ventilation vs inspired CO2.
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DOI：
10.1378/chest.130.1.85
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发表时间：
2006-07
期刊：
影响因子：
9.6
通讯作者：
S. Sinclair;D. Kregenow;I. Starr;C. Schimmel;W. Lamm;M. Hlastala;E. Swenson
中科院分区：
文献类型：
--
作者：
S. Sinclair;D. Kregenow;I. Starr;C. Schimmel;W. Lamm;M. Hlastala;E. Swenson
研究目的高碳酸血症在急性肺损伤(ALI)动物模型中具有抗炎作用，并能改善正常肺的V/Q匹配。高碳酸血症对ALI患者V/Q匹配的影响是相互矛盾的。与对照组相比，ALI患者潮气量减少(VTS)引起的高碳酸血症与分流分数(QS/QT)增加有关。不同组间Vt的差异使得对V/Q匹配的高碳酸酸血症的评估变得困难。将二氧化碳添加到吸入气体中，可以比较相同Vt条件下的气体交换情况。我们推测，吸入二氧化碳(ICD)引起的高碳酸血症将改善ALI的气体交换，并优于因呼吸频率降低而导致的低分钟通气量(LVE)，而不是室速。设计大学麻醉新西兰大白兔的实验室研究。干预：用多重惰性气体消除技术对10只生理盐水溶液灌洗的动物进行V/Q关系的评估，这些动物以6mL/kg VTS和8 cm H2O的呼气末正压进行呼吸。每只兔随机分为呼吸减慢和10%ICD致高碳酸血症(PaCO_2，95~100 mm Hg)。结果ICD组和LVE组的PaO2均大于Eucapia组，但肺泡-动脉血氧分压差和PaO2/吸氧率无显著差异。与ICD和桉树相比，LVE的平均V/Q分布有统计学意义的降低。LVE期间呼吸机对数十二烷基硫酸钠和弥散指数的联合滞留排泄曲线均升高，提示呼吸机分布发生了不利的变化。LVE和ICD均不改变QS/QT。结论与桉树和ICD相比，LVE对整体气体交换和通气量分布有轻微损害，但不增加QS/QT。虽然ICD并不能显著改善气体交换，但它在达到“治疗性”高碳酸血症的抗炎效果方面可能优于LVE，因为它不会对气体交换产生不利影响，而且有可能使肺部酸化更均匀。
STUDY OBJECTIVES Hypercapnic acidosis has antiinflammatory effects in animal models of acute lung injury (ALI) and improves ventilation-perfusion (V/Q) matching in normal lungs. The effect of hypercapnia on V/Q matching in ALI is conflicting. Hypercapnic acidosis produced by reduced tidal volumes (Vts) was associated with an increased shunt fraction (QS/QT) in patients with ALI compared with control subjects. Vt differences between groups make the assessment of hypercapnic acidosis on V/Q matching difficult. Adding CO2 to the inhaled gas allows the comparison of gas exchange under identical Vt conditions. We hypothesized the presence of hypercapnic acidosis from inspired carbon dioxide (ICD) would improve gas exchange in ALI and would be superior to that of low minute ventilation (LVe) produced by reduced respiratory rate, rather than Vt. DESIGN University laboratory study of anesthetized New Zealand White rabbits. INTERVENTIONS Assessment of V/Q relationships using the multiple inert gas elimination technique was performed in 10 saline solution-lavaged animals, which were ventilated with 6 mL/kg Vts and a positive end-expiratory pressure of 8 cm H2O. Each rabbit was studied while it was in eucapnia, followed by hypercapnia (Pa(CO2), 95 to 100 mm Hg) induced by LVe from decreased respiratory rate and by 10% ICD, in random order. MEASUREMENTS AND RESULTS The Pa(O2) was greater in ICD and LVe compared to eucapnia, but no significant differences in alveolar-arterial oxygen pressure difference or Pa(O2)/fraction of inspired oxygen ratio occurred. LVe statistically reduced the mean V/Q distributions compared with ICD and eucapnia. Log SDs of ventilation and combined retention and excretion curves of the dispersion index were both increased during LVe, indicating the presence of unfavorable changes in ventilation distribution. Neither LVe nor ICD altered the QS/QT. CONCLUSIONS LVe slightly impairs overall gas exchange and ventilation distribution, but does not increase QS/QT compared with eucapnia and ICD. While ICD does not significantly improve gas exchange, it may be superior to LVe in achieving the antiinflammatory effects of "therapeutic" hypercapnia, since it does not adversely alter gas exchange and has the potential to make the lung more uniformly acidotic.