Hopkins S R, Schoene R B, Henderson W R, Spragg R G, Martin T R, West J B
Department of Medicine, University of California, San Diego, USA.
Am J Respir Crit Care Med. 1997 Mar;155(3):1090-4. doi: 10.1164/ajrccm.155.3.9116992.
The blood-gas barrier must be very thin to allow gas exchange and it is therefore subjected to high mechanical stresses when the capillary pressure rises. In some animals, such as the thoroughbred race-horse during intense exercise, the stresses are so large that the capillaries fail and bleeding occurs. We tested the hypothesis that, in elite human athletes, the high capillary pressure that occurs during severe exercise alters the structure and function of the blood-gas barrier. We performed bronchoalveolar lavage (BAL) in six healthy athletes, who had a history suggestive of lung bleeding, 1 h after a 7-min cycling race simulation and four normal sedentary control subjects who did not exercise before BAL. The athletes had higher (p < 0.05) concentrations of red blood cells (0.51 x 10(5) versus 0.01 x 10(5).ml-1), total protein (128.0 versus 94.1 micrograms/ml), albumin (65.6 versus 53.0 micrograms/ml), and leukotriene B4 (LTB4) (243 versus 0 pg/ml) in BAL fluid than control subjects. The proportion of neutrophils was similar in athletes and control subjects but the proportion of lymphocytes in BAL fluid was reduced (p < 0.05). There were no differences in levels of surfactant apoprotein A, tumor necrosis factor bioactivity, lipopolysaccharide, or interleukin-8 (IL-8) between groups. These results show that brief intense exercise in athletes with a history suggestive of lung bleeding alters blood-gas barrier function resulting in higher concentrations of red cells and protein in BAL fluid. The lack of activation of proinflammatory pathways (except LTB4) in the airspaces supports the hypothesis that the mechanism for altered blood-gas barrier function is mechanical stress.
血气屏障必须非常薄以便进行气体交换，因此当毛细血管压力升高时，它会承受很高的机械应力。在一些动物中，比如纯种赛马在剧烈运动时，这种应力非常大以至于毛细血管破裂并发生出血。我们检验了这样一个假设：在优秀的人类运动员中，剧烈运动时出现的高毛细血管压力会改变血气屏障的结构和功能。我们对六名有肺出血病史的健康运动员在进行7分钟自行车比赛模拟后1小时进行了支气管肺泡灌洗（BAL），并对四名正常久坐的对照受试者在灌洗前未进行运动的情况下进行了同样操作。运动员的支气管肺泡灌洗液中红细胞（0.51×10⁵对0.01×10⁵/ml）、总蛋白（128.0对94.1微克/毫升）、白蛋白（65.6对53.0微克/毫升）和白三烯B4（LTB4）（243对0皮克/毫升）的浓度高于对照受试者。运动员和对照受试者中性粒细胞的比例相似，但支气管肺泡灌洗液中淋巴细胞的比例降低（p<0.05）。两组之间表面活性物质载脂蛋白A、肿瘤坏死因子生物活性、脂多糖或白细胞介素-8（IL-8）的水平没有差异。这些结果表明，有肺出血病史的运动员进行短暂剧烈运动后会改变血气屏障功能，导致支气管肺泡灌洗液中红细胞和蛋白质浓度升高。肺泡腔中促炎途径（除LTB4外）未被激活支持了血气屏障功能改变的机制是机械应力这一假设。
