Hyperinflation and its effects on upper and lower extremities exercise in patients with COPD and controls. A longitudinal study

Introduction: In chronic obstructive pulmonary disease (COPD), a decreased inspiratory/total lung capacity ratio (IC/TLC), is associated with dynamic hyperinflation (DH) and poor exercise capacity. The association to upper extremity force measured by handgrip strength (HGS) and 6 minute walk distance has not been described. We hypothesized that IC/TLC affects muscle strength of upper and lower extremities affecting HGS and the six minute walk test (6MWD) performance. Methods: We prospectively measured lung function, HGS and 6MWD in 27 patients with COPD and 12 healthy nonsmoking individuals twice, 1 year apart. The patients were classified according to level of hyperinflation in 2 groups, IC/TLC > or ≤ 25%. Results: Patients with COPD had reduced lung function, static hyperinflation, reduced HGS and 6MWD compared to the controls on both evaluations (p < 0.01). There was a statistically significant deterioration in HGS, IC/TLC and 6MWD after 1 year follow up in the COPD compared to the control group (p < 0.001). More hyperinflation (IC/TLC < .25) was associated with lower HGS and 6MWD (p < 0.001). Changes in IC/TLC correlated with changes in HGS (r = 0.429, p < 0.05) . A multivariate analysis determined that IC/TLC and heart rate were independent factors associated to HSG and to 6MWD. Conclusion: Handgrip strength and 6MWD are reduced in patients with COPD, particularly in patients with hyperinflation with evidence of longitudinal deterioration not seen in controls. This suggests that resting hyperinflation may exert a detrimental effect on cardiac function and play a role in the reduced exercise performance in COPD patients.