Lung function and peak oxygen uptake in chronic obstructive pulmonary disease phenotypes with and without emphysema

Area of Science:

• Pulmonary Medicine
• Cardiorespiratory Physiology
• Chronic Obstructive Pulmonary Disease (COPD) Research

Background:

• Previous studies on the association between forced expiratory lung volume in one second (FEV1) and peak oxygen uptake (VO2peak) in COPD have not accounted for sex, age, and height variations in lung volumes.
• Comparisons of VO2peak between COPD phenotypes, such as emphysema (E-COPD) and non-emphysema (NE-COPD), have also lacked consideration for the demographic spread of spirometric measures.

Purpose of the Study:

• To assess the association between the FEV1 Z-score and VO2peak in a cohort of COPD patients (n=186).
• To investigate whether this association differs between E-COPD and NE-COPD phenotypes.
• To compare VO2peak differences between COPD phenotypes using FEV1 Z-score and standardized percent predicted FEV1 (ppFEV1).

Main Methods:

• Linear regression models were used to assess the association of FEV1 Z-score with VO2peak.
• Stratified analyses were performed to examine associations within E-COPD and NE-COPD phenotypes.
• E-COPD and NE-COPD were defined based on the transfer factor of the lung for carbon monoxide relative to the lower limits of normal (LLN).

Main Results:

• A one-unit reduction in FEV1 Z-score was associated with a 1.9 ml/kg/min decrease in VO2peak.
• The association was stronger in E-COPD (2.2 ml/kg/min lower VO2peak per unit FEV1 Z-score reduction) compared to NE-COPD (1.2 ml/kg/min).
• Despite a stronger association in E-COPD, the difference was not statistically significant between phenotypes (p=0.153). E-COPD showed significantly lower VO2peak compared to NE-COPD, independent of FEV1 measures.

Conclusions:

• FEV1 Z-score is positively associated with VO2peak in COPD patients.
• While the association is stronger in the emphysema phenotype, it does not differ significantly between E-COPD and NE-COPD.
• The relationship between FEV1 and VO2peak, as well as VO2peak differences between COPD phenotypes, appears independent of sex, age, and height-related lung volume variations.