Interpretation of changes in DLCO and pulmonary function after running five miles

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 (DLCO) and cardiac output (Q) 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 DLCO did not change, significant change in cardiac output occurred during the DLCO 10 sec breathhold maneuver. The pre-run DLCO maneuver produced a fall in stroke volume (SV) with an increase in HR while maintaining Q. The post-run Q fell during the DLCO 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 DLCO to increase immediately after exercise when HR and presumably Q is elevated. To avoid any misinterpretation of changes in DLCO produced by exercise, Q should be measured at the time of the DLCO determination. Our findings suggest that values for DLCO post-exercise are entirely appropriate for the pulmonary blood flow at the time of the DLCO maneuver.