Small Pulmonary Artery and Vein Volumes Independently Predict Oxygen Desaturation in Smokers.

BACKGROUND AND RESEARCH QUESTION: Multiple factors affect oxygen levels in chronic obstructive pulmonary disease (COPD), including airflow limitation, emphysema, ventilation-perfusion mismatch, cardiac dysfunction, and pulmonary vascular remodeling. We investigated the association of small pulmonary vein and artery volume with oxygen saturation.

METHODS

In the COPD Genetic Epidemiology (COPDGene®) study cohort, current and former smokers were characterized with questionnaires, spirometry, oxygen saturation measurements, and computed tomography (CT). On CT scans, small pulmonary vein and artery volume (diameter <1mm) were quantified with automated image analysis. Associations of small vein and artery volume with oxygen saturation and supplemental oxygen use were investigated with multivariable regression, correcting for body surface area, clinical (including emphysema, forced expiratory volume in 1 second percentage predicted, and coronary calcium), and technical covariates.

RESULTS

A total of 8931 individuals were included with a mean age of 60.0±9.0 years. Of the participants, 52.7% were male. Half were current smokers (50.7%), and the number of pack years was 44.5±25.0. Median saturation was 97% (interquartile range 95%–98%), and 1040 (11.6%) participants used supplemental oxygen. Oxygen saturation decreased with 0.14% (-0.25, -0.03) (p=0.01) for 1mL/m2 each increase in vein volume and 0.15% (-0.21, -0.09) for artery volume. Oxygen users had higher small vein volume (3.01±0.61mL/m2) compared to those without oxygen (2.68±0.53mL/m2). Each 1mL/m2 increase in vein volume (adjusted odds ratio [OR] 1.51 [1.25, 1.84] p<0.001) and artery volume (OR 1.16 [1.02, 1.31]) was associated with more supplemental oxygen use.

INTERPRETATION: In current and former smokers, higher small pulmonary vein and artery volume were associated with lower resting saturation and more supplemental oxygen use, independent of lung disease severity or technical parameters. This suggests a role for vascular remodeling in smoking-related disease.