Restricted postexercise pulmonary diffusion capacity does not impair maximal transport for O2.

We evaluated whether the postexercise reduction of pulmonary diffusion capacity for carbon monoxide (DLco) is influenced by a second bout of rowing and whether it affects arterial O2 tension during maximal exercise. After exercise, DLco was reduced [from a median of 37 (range of 30-44) to 34 (27-40) ml.min-1.mmHg-1; n = 21; P < 0.001], and both the membrane diffusion capacity [from 80 (58-139) to 68 (54-104) ml.min-1.mmHg-1] and the pulmonary capillary blood volume [from 88 (74-119) to 79 (61-121) ml; P < 0.01] were affected. A second bout of exercise did not influence DLco or membrane diffusion capacity (n = 7), but during both bouts arterial O2 tension was reduced [from 105 (91-110) to 91 (77-102) Torr; P < 0.001] and arterial O2 saturation decreased [from 0.98 (0.97-0.99) to 0.95 (0.86-0.96); P < 0.001]. Furosemide (iv) did not affect DLco (n = 7), suggesting that it was influenced by the central blood volume rather than by pulmonary edema.