Snapper J R, Harris T R, Brigham K L
J Appl Physiol Respir Environ Exerc Physiol. 1982 Jun;52(6):1591-7. doi: 10.1152/jappl.1982.52.6.1591.
The effects of changing cardiac output and lung mass on pulmonary capillary surface area, lung water, and hemodynamics were studied in eight sheep. 51Cr-erythrocytes, 125I-albumin, 3H2O, and [14C]urea were injected into the right atrium, and timed samples were collected from the aorta for the calculation of cardiac output (CO), extravascular lung water (EVLW), and permeability-surface area product (PS) for [14C]urea. CO was varied by opening and closing arteriovenous shunts, and lung mass was decreased by first tying off the left lung followed by tying off the right lower lobe. Pulmonary arterial pressure (r = -0.741) and pulmonary vascular resistance (r = -0.700) increased as lung mass was decreased. CO decreased slightly (r = -0.470 while left atrial pressure was not changed (r = -0.144) by decreasing lung mass. There was a close correlation between EVLW and lung mass (r = 0.944) and between [14C]urea PS and lung mass (r = 0.672). We were able to demonstrate that [14C]urea behaves as a diffusion-limited tracer in a single pass through the lungs, since [14C]urea extraction decreased as flow per unit mass increased. These results support the clinical use of multiple-tracer studies to measure EVLW and [14C]urea PS.
在八只绵羊身上研究了心输出量和肺质量变化对肺毛细血管表面积、肺水含量和血流动力学的影响。将51Cr标记的红细胞、125I标记的白蛋白、3H2O和[14C]尿素注入右心房，并从主动脉采集定时样本，以计算心输出量（CO）、血管外肺水（EVLW）和[14C]尿素的通透表面积乘积（PS）。通过开放和关闭动静脉分流来改变CO，通过先结扎左肺，然后结扎右下叶来减少肺质量。随着肺质量的减少，肺动脉压（r = -0.741）和肺血管阻力（r = -0.700）增加。减少肺质量时，CO略有下降（r = -0.470），而左心房压力未改变（r = -0.144）。EVLW与肺质量之间（r = 0.944）以及[14C]尿素PS与肺质量之间（r = 0.672）存在密切相关性。我们能够证明，[14C]尿素在单次通过肺部时表现为扩散限制型示踪剂，因为随着单位质量流量的增加，[14C]尿素的摄取量会减少。这些结果支持了多示踪剂研究在测量EVLW和[14C]尿素PS方面的临床应用。
