Key result
Sustained, heavy exercise significantly increased pulmonary perfusion heterogeneity in the coronal plane, as measured by relative dispersion (from 0.62 to 0.82, P<0.0001).
Why the study?
Does sustained, heavy exercise increase the spatial heterogeneity of pulmonary perfusion in athletic subjects?
Does sustained, heavy exercise increase the spatial heterogeneity of pulmonary perfusion in athletic subjects?
Absolute Event Rate: 0.82% vs 0.62%
p-value: p=<0.0001
Sustained heavy exercise significantly increases spatial perfusion heterogeneity in the coronal plane, which correlates with ventilation-perfusion heterogeneity and may suggest exercise-induced interstitial pulmonary edema.
May signal transient V/Q mismatch in athletes; leaves open clinical relevance and requires prospective confirmation.
Exercise presents a considerable stress to the pulmonary system and ventilation-perfusion (Va/Q) heterogeneity increases with exercise, affecting the efficiency of gas exchange. In particular, prolonged heavy exercise and maximal exercise are known to increase Va/Q heterogeneity and these changes persist into recovery. We hypothesized that the spatial heterogeneity of pulmonary perfusion would be similarly elevated after prolonged exercise. To test this, athletic subjects (n = 6, Vo(2max) = 61 ml. kg(-1).min(-1)) with exercising Va/Q heterogeneity previously characterized by the multiple inert gas elimination technique (MIGET), performed 45 min of cycle exercise at approximately 70% Vo(2max). MRI arterial spin labeling measures of pulmonary perfusion were acquired pre- and postexercise (at 20, 40, 60 min post) to quantify the spatial distribution in isogravitational (coronal) and gravitationally dependent (sagittal) planes. Regional proton density measurements allowed perfusion to be normalized for density and quantified in milliliters per minute per gram. Mean lung density did not change significantly in either plane after exercise (P = 0.19). Density-normalized perfusion increased in the sagittal plane postexercise (P =or <0.01) but heterogeneity did not (all P >or= 0.18), likely because of perfusion redistribution and vascular recruitment. Density-normalized perfusion was unchanged in the coronal plane postexercise (P = 0.66), however, perfusion heterogeneity was significantly increased as measured by the relative dispersion [RD, pre 0.62(0.07), post 0.82(0.21), P < 0.0001] and geometric standard deviation [GSD, pre 1.74(0.14), post 2.30(0.56), P < 0.005]. These changes in heterogeneity were related to the exercise-induced changes of the log standard deviation of the ventilation distribution, an MIGET index of Va/Q heterogeneity (RD R(2) = 0.68, P < 0.05, GSD, R(2) = 0.55, P = 0.09). These data are consistent with but not proof of interstitial pulmonary edema as the mechanism underlying exercise-induced increases in both spatial perfusion heterogeneity and Va/Q heterogeneity.
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Burnham et al. (2009) studied Healthy athletic males (n=6). Sustained, heavy exercise vs. Pre-exercise baseline was evaluated on Relative dispersion (RD) of density-normalized perfusion in the coronal plane (p=<0.0001). Sustained, heavy exercise significantly increased pulmonary perfusion heterogeneity in the coronal plane, as measured by relative dispersion (from 0.62 to 0.82, P<0.0001).
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