CT-detected pulmonary vascular changes are associated with measures of small airways disease in smokers

<bold>Background:</bold> Pulmonary vascular changes occur early in the development of COPD. CT measures can quantify these changes in vivo. Understanding the natural history of vascular pathology may enable new approaches to early diagnosis and disease stratification. <bold>Aims:</bold> We have previously demonstrated a relationship between small pulmonary vessel volume and decline in FEV1. Here we seek to identify whether pulmonary vascular changes are associated with physiological measures of early COPD. <bold>Methods:</bold> The British Early COPD Network observational study recruited current smokers aged 30-45 under ethically approved informed consent. Participants had normal spirometry or mild airflow limitation and underwent thoracic CT, spirometry and oscillometry. CT images were segmented and volume of vessels with cross sectional area <5mm² (BV5), total pulmonary vascular volume (TPVV) and total lung volume (TLV) were measured. <bold>Results:</bold> In a preliminary analysis of 20 scans, those with physiological features of small airways disease (defined as MEF25-75% <65% predicted, R5-R20 ≥0.07 kPa/L/s or R5-R20 z-score >1.64) at any time over 4 years of follow-up had significantly higher BV5/TPVV (mean difference +/-SE. 098+/-.029, p=.004) and BV5/TLV (mean difference. 473mL/dL +/-.119, p<.001). Positive correlations with reactance area (AX, cmH₂O/L) and R5-R20 (kPa/L/s and z-score) were seen in TPVV/TLV, BV5/TPVV and BV5/TLV, suggesting enlargement of small vessels, though in a preliminary group of 20 this only reached significance between AX and BV5/TLV (r=.447, p=.048). <bold>Conclusions:</bold> An enlargement of small vessels detected on CT was associated with markers of small airways disease in an early COPD cohort.