SUSTAINED SUBMAXIMAL EXERCISE DOES NOT ALTER THE INTEGRITY OF THE LUNG BLOOD-GAS BARRIER IN ELITE ATHLETES

The extreme thinness of the pulmonary blood-gas barrier results in hig h mechanical stresses in the capillary wall when the capillary pressur e rises during exercise. We have previously shown that, in elite cycli sts, 6-8 min of maximal exercise increase blood-gas barrier permeabili ty and result in higher concentrations of red blood cells, total prote in, and leukotriene B-4 in bronchoalveolar lavage (BAL) fluid compared with results in sedentary controls. To test the hypothesis that stres s failure of the barrier only occurs at the highest level of exercise, we performed BAL in six healthy athletes after 1 h of exercise at 77% of maximal O-2 consumption. Controls were eight normal nonathletes wh o did not exercise before BAL. In contrast with our previous study, we did not find higher concentrations of red blood cells, total protein, and leukotriene B-4 in the exercising athletes compared with control subjects. However, higher concentrations of surfactant apoprotein A an d a higher surfactant apoprotein A-to-phospholipid ratio were observed in the athletes performing prolonged exercise, compared with both the controls and the athletes from our previous study. These results sugg est that, in elite athletes, the integrity of the blood-gas barrier is altered only at extreme levels of exercise.