Yamaguchi K, Mori M, Kawai A, Asano K, Takasugi T, Umeda A, Yokoyama T
Department of Medicine, School of Medicine, Keio University, Tokyo, Japan.
Adv Exp Med Biol. 1992;316:299-309. doi: 10.1007/978-1-4615-3404-4_35.
To assess a significant role of hypoxic pulmonary vasoconstriction, HPV, on maintaining the gas exchange efficiency in acute lung injury, 24 mongrel dogs were treated with intravenously injecting 0.07 ml/kg of oleic acid. Hemodynamic and gas-exchange parameters were investigated at varied inspired O2 concentration, FIO2. To know a possible contribution of vasoactive prostanoids in regulating vascular reactivity under these circumstances, observations were repeated after infusion of indomethacin. The impairment of gas exchange in injured lungs was examined by measuring the fractional retention, R, of the gas in arterial blood. For this evaluation, a normal saline containing five foreign inert gases such as sulfur hexafluoride, SF6, ethane, cyclopropane, halothane and diethyl ether was infused at a constant rate through a peripheral vein. After a steady state was established, the expired gas was collected and the samples of both arterial and mixed venous blood were simultaneously taken for the inert-gas analysis. The concentrations of the indicator gases in the samples were measured in terms of a gas chromatograph equipped with an electron capture detector for SF6 and a flame ionization detector for the other four gases. Although pulmonary vascular resistance, PVR, after injecting oleic acid at FIO2 0.60 was significantly smaller than that obtained at FIO2 0.21, cardiac output, QT as well as extravascular lung water were not different between the two conditions. R value for the indicator gas was consistently lower at FIO2 0.60 irrespective of the gas species. As increasing FIO2, R estimate concerning SF6, RSF6, rational index of the fractional blood flow perfusing shunt area, decreased significantly. Administration of indomethacin caused the rise in PVR without an appreciable change in either QT or extravascular lung water but a considerable diminution in R value for the inert gas. RSF6 after infusion of indomethacin decreased from 0.35 to 0.27, accompanied by a significant rise in arterial PO2 from 84 to 99 Torr. The findings are highly compatible with the idea that HPV is distinctly attenuated in diseases areas induced by oleic acid probably due to a local accumulation of vasodilator prostanoids. Inhibiting prostanoid biosynthesis may selectively enhance the vascular reactivity to O2 in shunt vessels and may redistribute the perfusion from shunt to relatively normal areas, thereby improving gas exchange at alveolar region without altering the total amount of extravascular lung water.
为评估低氧性肺血管收缩（HPV）在急性肺损伤中维持气体交换效率的重要作用，对24只杂种犬静脉注射0.07 ml/kg油酸进行治疗。在不同的吸入氧浓度（FIO2）下研究血流动力学和气体交换参数。为了解在这些情况下血管活性前列腺素在调节血管反应性中的可能作用，在输注吲哚美辛后重复观察。通过测量动脉血中气体的分数潴留（R）来检查损伤肺中气体交换的受损情况。为此评估，通过外周静脉以恒定速率输注含有六种外来惰性气体（如六氟化硫、SF6、乙烷、环丙烷、氟烷和乙醚）的生理盐水。在建立稳定状态后，收集呼出气体，并同时采集动脉血和混合静脉血样本进行惰性气体分析。样本中指示气体的浓度通过配备用于SF6的电子捕获检测器和用于其他四种气体的火焰离子化检测器的气相色谱仪进行测量。尽管在FIO2 0.60时注射油酸后的肺血管阻力（PVR）显著低于在FIO2 0.21时获得的阻力，但两种情况下的心输出量（QT）以及血管外肺水并无差异。无论气体种类如何，在FIO2 0.60时指示气体的R值始终较低。随着FIO2升高，关于SF6的R估计值（RSF6），即灌注分流区域的分数血流的合理指数，显著降低。给予吲哚美辛导致PVR升高，QT或血管外肺水均无明显变化，但惰性气体的R值显著降低。输注吲哚美辛后的RSF6从0.35降至0.27，同时动脉血氧分压从84 Torr显著升至99 Torr。这些发现与以下观点高度相符，即HPV在油酸诱导的疾病区域明显减弱，可能是由于血管扩张性前列腺素的局部积累。抑制前列腺素生物合成可能选择性增强分流血管对氧的血管反应性，并可能将灌注从分流重新分配到相对正常的区域，从而在不改变血管外肺水总量的情况下改善肺泡区域的气体交换。
