Pulmonary Vascular Volume by Quantitative CT in Dyspneic Smokers with Minor Emphysema.

Reduced lung diffusing capacity for carbon monoxide (DL) at rest and increased ventilation ()-carbon dioxide output (CO) during exercise are frequent findings in dyspneic smokers with largely preserved FEV. It remains unclear whether low DL and high -CO are mere reflections of alveolar destruction (i.e. emphysema) or impaired pulmonary perfusion in non-emphysematous tissue contributes to these functional abnormalities. Sixty-four smokers (41 males, FEV= 84 ± 13%predicted) underwent pulmonary function tests, an incremental exercise test, and quantitative chest computed tomography. Total pulmonary vascular volume (TPVV) was calculated for the entire segmented vascular tree (VIDA Vision™). Using the median % low attenuation area (-950 HU), participants were dichotomized into "Trace" or "Mild" emphysema (E), each group classified into preserved reduced DL. Within each emphysema subgroup, participants with abnormally low DL showed lower TPVV, higher -CO, and exertional dyspnea than those with preserved DL ( < 0.05). TPVV ( = 0.34;  = 0.01), but not emphysema ( = -0.05;  = 0.67), correlated with lower DL after adjusting for age and height. Despite lower emphysema burden, Trace-E participants with reduced DL had lower TPVV, higher dyspnea, and lower peak work rate than the Mild-E with preserved DL ( < 0.05). Interestingly, TPVV (but not emphysema) correlated inversely with both dyspnea-work rate ( = -0.36,  = 0.004) and dyspnea- slopes ( = -0.40,  = 0.001). Reduced pulmonary vascular volume adjusted by emphysema extent is associated with low DL and heightened exertional ventilation in dyspneic smokers with minor emphysema. Impaired perfusion of non-emphysematous regions of the lungs has greater functional and clinical consequences than hitherto assumed in these subjects.