Relationship of Pulmonary Vascular Structure and Function With 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 are associated with higher exercise capacity (peak rate of oxygen consumption [V˙opeak]).

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

Study Design And Methods: 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 mm in cross-sectional area (BV5), and volume for vessels between 5 and 10 mm 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˙opeak was evaluated via incremental cardiopulmonary exercise testing.

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

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