Relationship of Pulmonary Vascular Structure and Function With Exercise Capacity in Health and COPD

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 are associated with higher exercise capacity (peak rate of oxygen consumption [V˙o₂peak]).

Is there a cross-sectional association between the pulmonary vasculature and V˙o₂peak? We hypothesized that those with higher CT blood vessel volumes and pulmonary diffusing capacity for carbon monoxide (Dlco) would have higher V˙o₂peak, independent of airflow limitation.

Participants from the Canadian Cohort Obstructive Lung Disease (CanCOLD) study were categorized as follows: participants with normal spirometry who had never smoked (n = 263), participants with normal spirometry who had ever smoked (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. V˙o₂peak was evaluated via incremental cardiopulmonary exercise testing.

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 V˙o₂peak. Interaction effects were observed between COPD and TVV, BV5, and BV5-10, indicating a weaker association between pulmonary vascular volumes and V˙o₂peak in COPD.

Our results suggest that pulmonary vascular structure and Dlco are independently associated with V˙o₂peak, regardless of severity of airflow limitation and emphysema, suggesting that these associations are not limited to COPD.