Small changes in lung function in runners with marathon-induced interstitial lung edema

The purpose of this study was to assess lung function in runners with marathon-induced lung edema. Thirty-six (24 males) healthy subjects, 34 (SD 9) years old, body mass index 23.7 (2.6) kg/m(2) had posterior/anterior (PA) radiographs taken 1 day before and 21 (6) minutes post marathon finish. Pulmonary function was performed 1-3 weeks before and 73 (27) minutes post finish. The PA radiographs were viewed together, as a set, and evaluated by two experienced readers separately who were blinded as to time the images were obtained. Radiographs were scored for edema based on four different radiological characteristics such that the summed scores for any runner could range from 0 (no edema) to a maximum of 8 (severe interstitial edema). Overall, the mean edema score increased significantly from 0.2 to 1.0 units (P < 0.01), and from 0.0 to 2.9 units post exercise in the six subjects that were edema positive (P = 0.03). Despite a 2% decrease in forced vital capacity (FVC, P = 0.024) and a 12% decrease in alveolar-membrane diffusing capacity for carbon monoxide (DmCO, P = 0.01), there was no relation between the change in the edema score and the change in DmCO or FVC. In conclusion, (1) mild pulmonary edema occurs in at least 17% of subjects and that changes in pulmonary function cannot predict the occurrence or severity of edema, (2) lung edema is of minimal physiological significance as marathon performance is unaffected, exercise-induced arterial hypoxemia is unlikely, and postexercise pulmonary function changes are mild.