Hansen T N, Le Blanc A L, Gest A L
J Appl Physiol (1985). 1985 Mar;58(3):812-8. doi: 10.1152/jappl.1985.58.3.812.
To assess the effects of alveolar hypoxia and angiotensin II infusion on distribution of blood flow to the lung we performed perfusion lung scans on anesthetized mechanically ventilated lambs. Scans were obtained by injecting 1-2 mCi of technetium-labeled albumin macroaggregates as the lambs were ventilated with air, with 10-14% O2 in N2, or with air while receiving angiotensin II intravenously. We found that both alveolar hypoxia and infusion of angiotensin II increased pulmonary vascular resistance and redistributed blood flow from the mid and lower lung regions towards the upper posterior region of the lung. We assessed the effects of angiotensin II infusion on filtration pressure in six lambs by measuring the rate of lung lymph flow and the protein concentration of samples of lung lymph. We found that angiotensin II infusion increased pulmonary arterial pressure 50%, lung lymph flow 90%, and decreased the concentration of protein in lymph relative to plasma. These results are identical to those seen when filtration pressure increases during alveolar hypoxia. We conclude that alveolar hypoxia and angiotensin II infusion both increase fluid filtration in the lung by increasing filtration pressure. The increase in filtration pressure may be the result of a redistribution of blood flow in the lung with relative overperfusion of vessels in some areas and transmission of the elevated pulmonary arterial pressure to fluid-exchanging sites in those vessels.
为了评估肺泡低氧和输注血管紧张素II对肺血流分布的影响，我们对麻醉状态下机械通气的羔羊进行了灌注肺扫描。在羔羊吸入空气、吸入含10 - 14%氧气的氮气或在静脉输注血管紧张素II的同时吸入空气时，通过注射1 - 2毫居里的锝标记白蛋白大聚合体来获取扫描图像。我们发现，肺泡低氧和血管紧张素II输注均增加了肺血管阻力，并使血流从中下肺区域重新分布至上肺后区域。我们通过测量肺淋巴液流速和肺淋巴液样本的蛋白质浓度，评估了血管紧张素II输注对6只羔羊滤过压的影响。我们发现，血管紧张素II输注使肺动脉压升高50%，肺淋巴液流速增加90%，并降低了淋巴液中相对于血浆的蛋白质浓度。这些结果与肺泡低氧时滤过压升高时所见的结果相同。我们得出结论，肺泡低氧和血管紧张素II输注均通过增加滤过压来增加肺内液体滤过。滤过压升高可能是肺内血流重新分布的结果，某些区域血管相对灌注过多，并将升高的肺动脉压传递至这些血管中的液体交换部位。
