Rationale Severe pulmonary hypertension (PH) is very uncommon in COPD, and a distinct phenotype has been hypothesised. We aimed to evaluate whether CT can help to recognise this condition non-invasively by measuring small pulmonary vessels.

Material and methods Patients with COPD who underwent pulmonary function tests, unenhanced CT of the chest and right heart catheterisation (RHC) during a period of stability were included in the study. From 105 included patients, 20 patients with COPD with severe PH (mean pulmonary arterial pressure, mPAP>35 mm Hg) were compared with 20 FEV₁-matched and age-matched patients with COPD with mild or without PH (mPAP<35 mm Hg). The percentage of total cross-sectional area of vessels less than 5 mm² normalised by lung area (%CSA_<5) and 5–10 mm² (%CSA_5–10), the mean number of cross-sectioned vessels (CSNs) and bronchial wall thickness (WT) were measured on CT examination and compared between groups. Paw scores combining PaO₂ measurement and CT parameters best correlated with mPAP were compared by receiver operating characteristic analysis to predict severe PH in COPD.

Results Patients with severe PH COPD had higher %CSA and CSN values than those of patients with COPD without severe PH. Using multiple regression analysis, %CSA_<5 and WT were the best predictors of mPAP in patients with and without severe PH, respectively. A score combining %CSA_<5, PaO₂ and WT best predicted severe PH in patients with COPD.

Conclusions CT measurements of small vessels support a distinct vessel-related phenotype in patients with COPD with severe PH, and combined with WT and PaO₂ parameters in the paw score, which may offer a non-invasive tool to select patients for RHC.