Fig. 1

Correlation between respiratory function and cardiopulmonary exercise testing (CPET) indices. The upper two panels show the relationship between FEV1.0/FVC and the Y-intercept of V̇E/V̇CO₂ in the convex group (A-1) and the non-convex group (A-2). The lower two panels show the relationship between FEV1.0/FVC and the difference between the minimum V̇E/V̇CO₂ and V̇E/V̇CO₂ slopes in the convex (B-1) and non-convex groups (B-2). V̇E/V̇CO₂: ventilatory equivalent for carbon dioxide production; FEV1.0/FVC: forced expiratory volume in 1 s as a percent of forced vital capacity;