Ehrhart I C, McCloud L L, Orfanos S E, Catravas J D, Hofman W F
Department of Physiology, Medical College of Georgia, Augusta 30912-3000.
J Appl Physiol (1985). 1994 Jun;76(6):2342-7. doi: 10.1152/jappl.1994.76.6.2342.
The elevated cardiac output associated with exercise increases lung lymph flow and may increase extravascular lung water. However, it is not known if extremely elevated cardiac output alters pulmonary vascular permeability. The hematocrit-protein method was used to determine the solvent drag reflection coefficient, an index of vascular permeability to proteins, in the isolated blood-perfused canine lung lobe. Microvascular pressure was obtained by double vascular occlusion. Lobes filtered fluid during perfusion at normal flow, 0.451 +/- 0.005 l/min (LF; n = 8), or high flow, 2.319 +/- 0.080 l/min (HF; n = 7). In the LF, venous pressure was elevated to 19.0 +/- 0.5 Torr to induce filtration, whereas Pv was 3.3 +/- 0.1 Torr in the HF. In HF vs. LF, respectively, arterial pressure was 61.4 +/- 7.1 vs. 28.0 +/- 1.0 Torr (P < 0.05), microvascular pressure was 31.9 +/- 3.0 vs. 22.2 +/- 0.9 Torr (P < 0.05), and sigma was 0.52 +/- 0.07 vs. 0.51 +/- 0.02 (P > 0.05). The fivefold increase in blood flow did not alter pulmonary vascular permeability to proteins; however, the capillary filtration coefficient was fivefold greater in the HF vs. LF group (0.328 +/- 0.059 vs. 0.067 +/- 0.007; P < 0.002). These data are compatible with enzyme activity measures indicating a direct linear relationship between blood flow rate and perfused pulmonary microvascular surface area. Although the data do not rule out the possibility of increased pulmonary vascular permeability to water during very elevated blood flow rates, the greater filtration rate during elevated flow is more likely related to increases in both microvascular pressure and surface area.
与运动相关的心输出量升高会增加肺淋巴液流量，并可能增加肺血管外含水量。然而，目前尚不清楚心输出量极度升高是否会改变肺血管通透性。采用血细胞比容-蛋白质法测定了在离体血液灌注犬肺叶中蛋白质的溶剂拖曳反射系数，这是血管对蛋白质通透性的一个指标。微血管压力通过双重血管阻断获得。肺叶在正常流量（0.451±0.005升/分钟，LF；n = 8）或高流量（2.319±0.080升/分钟，HF；n = 7）灌注期间进行滤过。在LF组中，静脉压力升高至19.0±0.5托以诱导滤过，而在HF组中Pv为3.3±0.1托。分别比较HF组和LF组，动脉压为61.4±7.1托对28.0±1.0托（P < 0.05），微血管压力为31.9±3.0托对22.2±0.9托（P < 0.05），且σ为0.52±0.07对0.51±0.02（P > 0.05）。血流量增加五倍并未改变肺血管对蛋白质的通透性；然而，HF组的毛细血管滤过系数比LF组大五倍（0.328±0.059对0.067±0.007；P < 0.002）。这些数据与酶活性测量结果一致，表明血流速率与灌注的肺微血管表面积之间存在直接线性关系。尽管这些数据并未排除在血流速率非常高时肺血管对水的通透性增加的可能性，但高流量期间更高的滤过率更可能与微血管压力和表面积的增加有关。
