Interpretation of changes in D lCO and pulmonary function after running five miles

Abstract

The purpose of this study was to evaluate changes in pulmonary function after running five miles. Of particular interest was the reaffirmation of the previously reported ‘uncoupling’ or dissociation of pulmonary diffusing capacity (D l CO) and cardiac output (Q̇) after moderate or strenuous exercise. Cardiopulmonary assessments were made on eight runners before and after completing three separate five mile runs. There were significant reductions in vital capacity (5.7%) and volume at closing with increases in residual volume (22.5%) and closing capacity post-run. Although D l CO did not change, significant change in cardiac output occurred during the D l CO 10 sec breathhold maneuver. The pre-run D l CO maneuver produced a fall in stroke volume (SV) with an increase in HR while maintaining Q̇. The post-run Q̇ fell during the D l CO maneuver due to a fall in SV with HR remaining constant. The primary basis for previous speculation of the development of a transient pulmonary edema during exercise has been the failure of D l CO to increase immediately after exercise when HR and presumably Q̇ is elevated. To avoid any misinterpretation of changes in D l CO produced by exercise, Q̇ should be measured at the time of the D l CO determination. Our findings suggest that values for D l CO post-exercise are entirely appropriate for the pulmonary blood flow at the time of theD l CO maneuver.