Mure M, Domino K B, Robertson T, Hlastala M P, Glenny R W
Department of Physiology and Biophysics, University of Washington, School of Medicine, Seattle, USA.
Anesthesiology. 1998 Aug;89(2):483-92. doi: 10.1097/00000542-199808000-00026.
Recent studies have questioned the classical gravitational model of pulmonary perfusion. Because the lateral position is commonly used during surgery, the authors studied the redistribution of pulmonary blood flow in the left lateral decubitus position using a high spatial resolution technique.
Distributions of pulmonary blood flow were measured using intravenously injected 15-microm diameter radioactive-labeled microspheres in eight halothane-anesthetized dogs, which were studied in the supine and left lateral decubitus positions in random order. Lungs flushed free of blood were air-dried at total lung capacity and sectioned into 1,498-2,396 (1.7 cm3) pieces per animal. Radioactivity was measured by a gamma counter, and signals were corrected for piece weight and normalized to mean flow.
Blood flow to the dependent left lung did not increase, and blood flow to the nondependent right lung did not decrease in the lateral position. The left lung received 39.3 +/-7.0% and 39.2+/-8.8% (mean +/- SD) of perfusion in the supine and left lateral positions, respectively. Detailed assessment of the spatial distributions of pulmonary blood flow revealed the lack of a gravitational gradient of blood flow in the lateral position. The distributions of blood flow did not differ in the supine and left lateral decubitus positions.
Perfusion to each lung did not change with movement from the supine to the left lateral position. These findings contradict the prediction of increased dependent lung and decreased nondependent lung blood flow based on the gravitational model. It was concluded that the distribution of blood flow in the lateral position in dogs is dominated by pulmonary vascular structure.
最近的研究对经典的肺灌注重力模型提出了质疑。由于手术中常用侧卧位，作者使用高空间分辨率技术研究了左侧卧位时肺血流的重新分布情况。
在8只氟烷麻醉的犬中，通过静脉注射直径15微米的放射性标记微球来测量肺血流分布，这些犬以随机顺序在仰卧位和左侧卧位进行研究。将肺冲洗干净并在肺总量下风干，然后每只动物切成1498 - 2396块（1.7立方厘米）。通过γ计数器测量放射性，并对信号进行组织块重量校正并归一化为平均流量。
在侧卧位时，下垂的左肺血流并未增加，非下垂的右肺血流也未减少。左肺在仰卧位和左侧卧位时分别接受39.3±7.0%和39.2±8.8%（平均值±标准差）的灌注。对肺血流空间分布的详细评估显示，侧卧位时不存在血流的重力梯度。仰卧位和左侧卧位时的血流分布无差异。
从仰卧位到左侧卧位的体位改变并未使每个肺的灌注发生变化。这些发现与基于重力模型预测的下垂肺血流增加和非下垂肺血流减少相矛盾。得出的结论是，犬侧卧位时的血流分布主要由肺血管结构决定。
