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

Reduced lung diffusing capacity for carbon monoxide (DL CO ) at rest and increased ventilation (⩒ E )-carbon dioxide output (⩒CO 2 ) during exercise are frequent findings in dyspneic smokers with largely preserved FEV 1 . It remains unclear whether low DL CO and high ⩒ E -⩒CO 2 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 1 = 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 versus reduced DL CO . Within each emphysema subgroup, participants with abnormally low DL CO showed lower TPVV, higher ⩒ E -⩒CO 2 , and exertional dyspnea than those with preserved DL CO (p