INDICATOR DILUTION LUNG WATER AND CAPILLARY BLOOD-VOLUME IN PROLONGED HEAVY EXERCISE IN NORMAL MEN

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Abstract
The indicator dilution quantity of extravascular water in the lung (idQwl) increased in exercise, but whether it was a real accumulation of fluid or was due to increased distribution of blood flow to previously unperfused regions of alveolar wall was unsettled. In 9 well-trained young men, idQwl and the pulmonary capillary blood volume were compared, as measured by the CO diffusing capacity procedure, at rest and after 10 and about 50 min of heavy work (150 watts) on a bicycle ergometer. After 10-min exercise, the heart rate was 72 .+-. 15 beats/min (mean .+-. SD) to 151 .+-. 23; cardiac output 6.0 .+-. 1 l/min to 17.7 .+-. 4.1; diffusing capacity, 46 .+-. 10 ml/min per mm Hg to 65 .+-. 11. These all remained constant between 10- and 50-min exercise. The idQwl increased from 178 .+-. 37 ml at rest to 219 .+-. 46 ml at 10 min and 233 .+-. 43 ml at 50 min, and pulmonary capillary blood volume increased from 140 .+-. 52 ml at rest to 220 .+-. 106 and 206 .+-. 98 at 10 and 50 min of exercise, respectively. All of the changes from rest to early exercise were significant (P < 0.05) by paired t test. There were no significant changes between early and late exercise. The early exercise increase in idQwl was probably due to redistribution of blood flow among and within alveolar walls. The absence of any increase in idQwl between early and late exercise was evidence against accumulation of lung fluid.