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Abstract

Twelve healthy male endurance trained athletes (mean age=24.8 ± 3.3 yrs, ht.=181.4 ± 4.8 cm., wt.=75.3 ± 6.7 kg., V02max=67.9 ± 5.6 ml/kg/min) served as subjects in an experiment to examine the effects of changing plasma volume on the relationship between pulmonary diffusion capacity (DLCO) and arterial blood oxygen saturation (%Sa02) following intense exercise. Subjects were divided into two groups based on the minimum %Sa02 recorded (HP47201A ear oximeter) during a V02max test; Non-desaturaters (ND=4) %SaO2>91.0 and Desaturaters (D=8) %SaO2<91.0. Each subject performed two, 5 minute bouts of exercise on separate days (Mijnhardt electrically-braked cycle ergometer) at a floating workload (mean=370 ± 30 W) assigned to maintain a V 0 2 equal to 90% of the subjects previously determined VC^max. The two trials (PLACEBO and LASIX) were assigned in random, double blind manner. In each of the trials the percent change in plasma volume (%dPV) was measured using hematocrit and hemoglobin values from 3cc blood samples taken immediately prior to each DLCO test. The DLCO (single-breath carbon monoxide method) was measured at three points during each trial; immediately prior to ingestion of the capsule, three hours later (one half hour prior to exercise) and one hour after completion of the exercise bout. The %Sa02 was monitored throughout the exercise period. In the PLACEBO trial both groups showed no significant changes in either %dPV or bodyweight. There was also no significant change in Pre-Pill to Pre-Exercise DLCO but a significant decrease (p2 showed a significant 6.54% decrease during intense exercise (p