Correlation Between the Six-Minute Walk Test and Pulmonary Function Test Parameters in Patients with Chronic Obstructive Pulmonary Disease: A Longitudinal Analysis.

Abstract

Background: The six-minute walk test (6MWT) serves as a straightforward and reliable measure of functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD), while pulmonary function tests (PFTs) provide detailed insights into lung mechanics through key parameters such as forced vital capacity (FVC), forced expiratory volume in one second (FEV1), the FEV1/FVC ratio, and peak expiratory flow (PEF). Elucidating the correlations between 6MWT performance and these PFT parameters can enhance clinical evaluation, disease monitoring, and therapeutic decision-making in COPD management.
Methods: This longitudinal correlational study analysed data from 21 COPD patients assessed at five distinct time points (baseline, 2 weeks, 3 weeks, 5 weeks, and 10 weeks), resulting in a total of 105 observations. Pearson correlation coefficients were computed to evaluate the relationships between 6MWT distance and PFT parameters, both overall and stratified by COPD severity grades (1-3).
Results: Across all observations, correlations were generally weak: FVC (r=0.078, p=0.429), FEV1 (r=0.178, p=0.069), FEV1/FVC (r=0.035, p=0.720), and PEF (r=0.149, p=0.129). Stratification by COPD grade revealed more nuanced patterns, with significant correlations in specific subgroups, including positive associations with PEF in grade 1 (r=0.276, p=0.046), FEV1/FVC in grade 2 (r=0.319, p=0.045), and both FVC (r=0.619, p=0.032) and PEF (r=0.795, p=0.002) in grade 3.
Conclusion: Overall correlations between 6MWT and PFT parameters are modest, they strengthen with increasing COPD severity, suggesting that 6MWT may be particularly valuable as a complementary tool in advanced disease stages for assessing functional limitations beyond spirometry measures.