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Daily Physical Activity in Patients with Chronic Obstructive Pulmonary Disease Is Mainly Associated with Dynamic Hyperinflation

¹ Servicio de Neumología, Hospital Universitario La Paz, Madrid; ² Sección de Neumología, Hospital Infanta Sofía, Madrid; ³ Servicio de Bioquímica, Hospital Universitario La Paz, Madrid; and ⁴ Investigation Unit, Hospital Universitario La Paz, Madrid, Spain

Correspondence and reqests for reprints should be addressed to Francisco Garcia-Rio, Ph.D., Senior Consultor, Alfredo Marquerie 11, izqda, 1° A, 28034 Madrid, Spain. E-mail: fgr01m{at}gmail.com

Rationale: Although the major limitation to exercise performance in patients with COPD is dynamic hyperinflation, little is known about its relation to daily physical activity.

Objectives: To analyze the contribution of dynamic hyperinflation, exercise tolerance, and airway oxidative stress to physical activity in patients with COPD.

Methods: In a cross-sectional study, we included 110 patients with moderate to very severe COPD. Daily physical activity was measured using a triaxial accelerometer providing a mean of 1-minute movement epochs as vector magnitude units (VMU). Patients performed the 6-minute walk test, incremental exercise test with measurement of breathing pattern and operating lung volumes, and constant-work rate test at 75% of maximal work rate.

Measurements and Main Results: Using the GOLD stage and BODE index, we determined arterial blood gases, lung volumes, diffusing capacity, and biomarkers in exhaled breath condensate. Daily physical activity was lower in the 89 patients who developed dynamic hyperinflation than in the 21 who did not (n =161 [SD 70] vs. n = 288 [SD 85] VMU; P = 0.001). Physical activity was mainly related to distance walked in 6 minutes (r = 0.72; P = 0.001), O₂ (r = 0.63; P = 0.001), change in end-expiratory lung volume during exercise (r = –0.73; P = 0.001), endurance time (r = 0.61; P = 0.001), and 8-isoprostane in exhaled breath condensate (r = –0.67; P = 0.001). In a multivariate linear regression analysis using VMU as a dependent variable, dynamic hyperinflation, change in end-expiratory lung volume, and distance walked in 6 minutes were retained in the prediction model (r² = 0.84; P = 0.001).

Conclusions: Daily physical activity of patients with COPD is mainly associated with dynamic hyperinflation, regardless of severity classification.

Key Words: pulmonary disease • activities of daily living • respiratory mechanics • exercise • ventilation

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Reduction of physical activity in patients with chronic obstructive pulmonary disease is related to exacerbations and mortality. What This Study Adds to the Field In patients with moderate to very severe chronic obstructive pulmonary disease, daily physical activity is mainly associated with dynamic hyperinflation.