Background: Pulmonary vascular alteration is an important feature of chronic obstructive pulmonary disease (COPD), which is characterized by distal pulmonary vascular pruning in angiography. We aimed to further investigate the clinical relevance of pulmonary vasculature in COPD patients using non-contrast computed tomography (CT).
Methods: Seventy-one control subjects and 216 COPD patients completed the questionnaires, spirometry, and computed tomography (CT) scans within 1 month and were included in the study. Small pulmonary vessels represented by percentage of cross-sectional area of pulmonary vessels smaller than 5 mm² or 5– 10 mm² to the total lung fields (%CSA< 5 or %CSA5– 10, respectively) were measured using ImageJ software. Spearman correlation was used to investigate the relationship between %CSA< 5 and airflow limitation. A receiver operating characteristic (ROC) curve was built to evaluate the value of %CSA< 5 in discriminating COPD patients from healthy control subjects. Segmented regression was used to analyze the relationship between %CSA< 5 and %LAA-950 (percentage of low-attenuation areas less than − 950 HU).
Results: We found a significant correlation between %CSA< 5 and forced expiratory volume in one second (FEV1) percentage of predicted value (%pred) (r = 0.564, P < 0.001). The area under the ROC curve for the value of %CSA< 5 in distinguishing COPD was 0.816, with a cut-off value of 0.537 (Youden index J, 0.501; sensitivity, 78.24%; specificity, 71.83%). Since the relationship between %CSA< 5 and %LAA-950 was not constant, performance of segmented regression was better than ordinary linear regression (adjusted R², 0.474 vs 0.332, P < 0.001 and P < 0.001, respectively). As %CSA< 5 decreased, %LAA-950 slightly increased until an inflection point (%CSA< 5 = 0.524) was reached, after which the %LAA-950 increased apparently with a decrease in %CSA< 5.
Conclusion: %CSA< 5 was significantly correlated with both airflow limitation and emphysema, and we identified an inflection point for the relationship between %CSA< 5 and %LAA-950.
Keywords: computed tomography, pulmonary vascular pruning, airflow limitation, emphysema, chronic obstructive pulmonary disease