Pulmonary Vascular Structure and Function Are Related to Exercise Capacity in Health and COPD

Background: Although it is generally accepted that aerobic exercise training does not change lung structure or function, some work suggests that greater pulmonary vascular structure and function is associated with higher exercise capacity (peak oxygen consumption [Vo₂peak]).

Research question: Is there a cross-sectional association between the pulmonary vasculature and Vo₂peak? We hypothesized that those with higher CT blood vessel volumes and capacity of the lungs for carbon monoxide (Dlco) would have higher Vo₂peak, independent of airflow limitation.

Study design and methods: Participants from the Canadian Cohort Obstructive Lung Disease (CanCOLD) study were categorized as follows: never smokers with normal spirometry (n = 263), ever smokers with normal spirometry (n = 407), and COPD: individuals with spirometric airflow obstruction (n = 334). Total vessel volume (TVV), volume for vessels < 5 mm² in cross-sectional area (BV5), and volume for vessels between 5 and 10 mm² in cross-sectional area (BV5-10) were generated from CT scans and used as indices of pulmonary vascular structure. Dlco was used as an index of pulmonary microvascular function. Vo₂peak was evaluated via incremental cardiopulmonary exercise testing.

Results: General linear regression models revealed that even after controlling for FEV₁, emphysema severity, and body morphology, Dlco, TVV, BV5, and BV5-10, were independently associated with Vo₂peak. Interaction effects were observed between COPD and TVV, BV5, and BV5-10, indicating a weaker association between pulmonary vascular volumes and Vo₂peak in COPD.

Interpretation: Our results suggest that pulmonary vascular structure and Dlco are independently associated with Vo₂peak, regardless of severity of airflow limitation and emphysema, suggesting that these associations are not limited to COPD.