Nolop K B, Braude S, Taylor K M, Royston D
J Appl Physiol (1985). 1987 Mar;62(3):1244-9. doi: 10.1152/jappl.1987.62.3.1244.
Cardiopulmonary bypass (CPB) causes lung injury that occasionally progresses to the adult respiratory distress syndrome (ARDS). We measured the effect of 10 cmH2O of positive end-expiratory pressure (PEEP) on small solute and protein flux in dogs 1 wk before and 2 h after the completion of CPB. As an index of alveolar epithelial permeability, the clearance from lung to blood of inhaled technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) was measured. To assess microvascular endothelial integrity, the rate of accumulation in the lung interstitium of intravascular 113mIn-transferrin was measured. The clearance half time (t 1/2) for 99mTc-DTPA in the study dogs declined from 18.8 +/- 1.9 min (mean +/- SE) at base line to 9.4 +/- 2.0 min during PEEP (P less than 0.05). Two hours after CPB, the t 1/2 was 8.1 +/- 1.6 min at base line and unchanged during PEEP. The 113mIn-transferrin rate of accumulation was unchanged by PEEP before CPB. After CPB, the index was 3.25 +/- 0.95 slope/min X 10(-3) (P less than 0.05). Of the five dogs with a significant slope, four showed a decrease in microvascular flux during PEEP, although for the group the mean change in slope was not significant (P = 0.10). We conclude that the application of PEEP does not increase 99mTc-DTPA clearance in lungs already injured by CPB, and may actually decrease the apparent microvascular protein flux in some cases.
体外循环（CPB）可导致肺损伤，偶尔会进展为成人呼吸窘迫综合征（ARDS）。我们在犬类动物体外循环开始前1周和结束后2小时，测量了10 cmH2O呼气末正压（PEEP）对小溶质和蛋白质通量的影响。作为肺泡上皮通透性的指标，测量了吸入的99m锝标记二乙三胺五乙酸（99mTc-DTPA）从肺到血液的清除率。为评估微血管内皮完整性，测量了血管内113m铟转铁蛋白在肺间质中的蓄积速率。研究犬类动物中99mTc-DTPA的清除半衰期（t1/2）从基线时的18.8±1.9分钟（平均值±标准误）降至PEEP期间的9.4±2.0分钟（P<0.05）。体外循环后2小时，基线时t1/2为8.1±1.6分钟，PEEP期间无变化。CPB前PEEP对113m铟转铁蛋白的蓄积速率无影响。CPB后，该指标为3.25±0.95斜率/分钟×10^(-3)（P<0.05）。在五只斜率有显著变化的犬中，四只在PEEP期间微血管通量降低，尽管该组斜率的平均变化不显著（P = 0.10）。我们得出结论，在已受CPB损伤的肺中应用PEEP不会增加99mTc-DTPA清除率，在某些情况下实际上可能会降低表观微血管蛋白通量。
