Rimeika D, Sanchez-Crespo A, Nyren S, Lindahl S G E, Wiklund C U
Department of Cardiothoracic Surgery and Anaesthesiology, Karolinska University Hospital and Karolinska Institute, Stockholm, Sweden.
Acta Anaesthesiol Scand. 2009 Oct;53(9):1158-66. doi: 10.1111/j.1399-6576.2009.02018.x. Epub 2009 Jul 22.
Previous studies have shown that ventilation-perfusion matching is improved in the prone as compared with that in the supine position. Regional differences in the regulation of vascular tone may explain this. We have recently demonstrated higher production of nitric oxide in dorsal compared with ventral human lung tissue. The purpose of the present study was to investigate regional differences in actions by another vasoactive mediator, namely prostacyclin. The effects on gas exchange and regional pulmonary perfusion in different body positions were investigated at increased prostacyclin levels by inhalation of a synthetic prostacyclin analogue and decreased prostacyclin levels by unselective cyclooxygenase (COX) inhibition.
In 19 volunteers, regional pulmonary perfusion in the prone and supine position was assessed by single photon emission computed tomography using (99m)Tc macro-aggregated albumin before and after inhalation of iloprost, a stable prostacyclin analogue, or an intravenous infusion of a non-selective COX inhibitor, diclofenac. In addition, gas distribution was assessed in seven subjects using (99m)Tc-labelled ultra-fine carbon particles before and after iloprost inhalation in the supine position.
Iloprost inhalation decreased arterial PaO(2) in both prone (from 14.2+/-0.5 to 11.7+/-1.7 kPa, P<0.01) and supine (from 13.7+/-1.4 to 10.9+/-2.1 kPa, P<0.01) positions. Iloprost inhalation redistributed lung perfusion from non-dependent to dependent lung regions in both prone and supine positions, while ventilation in the supine position was distributed in the opposite direction. No significant effects of non-selective COX inhibition were found in this study.
Iloprost inhalation decreases arterial oxygenation and results in a more gravity-dependent pulmonary perfusion in both supine and prone positions in healthy humans.
先前的研究表明，与仰卧位相比，俯卧位时通气-灌注匹配得到改善。血管张力调节的区域差异可能对此作出解释。我们最近证明，与腹侧人肺组织相比，背侧人肺组织中一氧化氮的生成量更高。本研究的目的是调查另一种血管活性介质即前列环素作用的区域差异。通过吸入合成前列环素类似物使前列环素水平升高，并通过非选择性环氧化酶（COX）抑制使前列环素水平降低，研究其对不同体位下气体交换和区域肺灌注的影响。
在19名志愿者中，在吸入依洛前列素（一种稳定的前列环素类似物）或静脉输注非选择性COX抑制剂双氯芬酸之前和之后，使用（99m）锝大聚合白蛋白通过单光子发射计算机断层扫描评估俯卧位和仰卧位时的区域肺灌注。此外，在7名受试者中，在仰卧位吸入依洛前列素之前和之后，使用（99m）锝标记的超细碳颗粒评估气体分布。
吸入依洛前列素使俯卧位（从14.2±0.5降至11.7±1.7 kPa，P<0.01）和仰卧位（从13.7±1.4降至10.9±2.1 kPa，P<0.01）的动脉血氧分压均降低。吸入依洛前列素使俯卧位和仰卧位的肺灌注从非下垂肺区域重新分布到下垂肺区域，而仰卧位的通气分布方向相反。本研究未发现非选择性COX抑制有显著影响。
在健康人中，吸入依洛前列素会降低动脉氧合，并导致仰卧位和俯卧位时肺灌注更依赖重力。
