Cardiopulmonary Exercise Testing and Quantitative Chest CT in COPD: The Stronger Association of Emphysema Over Airway...

The relationship between cardiopulmonary function and chest structure, particularly the square root of wall area of a hypothetical airway with a luminal perimeter of 10 mm (Pi10), in patients with chronic obstructive pulmonary disease (COPD) remains unclear. This study aims to compare cardiopulmonary function across computed tomography (CT) phenotypes and to evaluate the association between emphysema, airway thickness and cardiopulmonary function, respectively.

Patients with stable COPD were recruited and underwent pulmonary function testing, CT, and cardiopulmonary exercise testing (CPET). Emphysema was assessed using the percentage of low attenuation areas < -950 Hounsfield units (%LAA-950), and airway wall thickness was evaluated with Pi10. Based on these two CT metrics, patients were categorized into four phenotypes: normal, emphysema-dominant (E-dominant), airway-dominant (A-dominant), and mixed. Pearson's correlation and Multiple linear regression were conducted to assess the relationship between %LAA-950, Pi10 and cardiopulmonary function.

Ninety-three patients were enrolled in this study. Individuals with E-dominant phenotype and mixed phenotype had lower FEV1/FVC, and those with E-dominant phenotype had worse ventilatory efficiency (V_D/V_Tpeak and V_E/VCO₂ slope). %LAA-950 showed negative correlations with VO_2peak (β = -0.288, p = 0.004) and VO_2peak%pred (β = -0.244, p = 0.027) and positive correlations with V_D/V_Tpeak (β = 0.272, p = 0.017), V_E/VCO_2AT (β = 0.285, p = 0.011) and V_E/VCO₂ slope (β = 0.276, p = 0.026). However, Pi10 exhibited no significant associations with the studied CPET variables.

Patients with emphysema are more likely to have reduced exercise endurance and ventilatory efficiency during exercise. Emphysema may be a better indicator of cardiopulmonary function than airway thickness.