LUNG DIFFUSION CAPACITY DURING 60 MIN's HIGH INTENSITY EXERCISE IN NORMOXIA1624:

After exercise at different intensities, particularly during hypoxia, a transient decrease in lung diffusion capacity (DLco) has been reported. Impairment of gas exchange has not been examined during constant load exercise in normoxia. Methods: 17 healthy, male subjects participated in the study(25±4 yrs, 77.1±6.5 kg, ˙VO2max 4.1 ±0.6 l·min-1). Subjects performed 60 min of cycling at approx. 86% of˙VO2max breathing room air. Cardiac output (˙Qc), ˙VO2 and DLco were measured by acetylene and CO rebreathing at rest, 8, 40, and 55 min during exercise, and 25 min after the test. Results: During the test, mean power was 232±37 W, mean˙VO2 was 3.6±.5 l·min-1, and mean ˙Qc was 22.1 l·min-1. DLco decreased during the test in 6 of the subjects (D) from 62.1±5.6 to 54.5±5.6 mm·min-1·mmHg-1 after 40 min of exercise (12.2%, p<0.05), whereas DLco was constant in the others (59.9±7.4 to 62.1±11.6 mm·min-1·mmHg-1). Power was nearly unchanged in both groups (change: -1.1 vs -2.6%, ns), but there was a tendency to lower ˙VO2 (-9.4% vs +9.8%, ns) and lower ˙Qc (-4.4% vs 2.7%, ns) in D compared to others. During the last minutes of the test, D had to decrease their power by 9.4%, ˙VO2 decreased 11.9%, ˙Qc by 8.9% and DLco by 16.7%. There was no sign. difference between DLco before and after the test. Conclusion: In 6 of 17 healthy subjects, DLco was decreased significantly after 40 min of constantly high intensive exercise. The decrease in DLco was not in proportion to smaller changes in ˙VO2 or ˙Qc, and these subjects could not maintain power in the remaining test. These findings indicate that intensive exercise can induce lung gas exchange abnormalities in healthy subjects.