title: Daily physical activity in patients with chronic obstructive pulmonary disease is mainly associated with dynamic hyperinflation.
abstract: BACKGROUND
  Although the major limitation to exercise performance in patients with COPD is dynamic hyperinflation, little is known about its relation to daily physical activity.
  
  
  OBJECTIVE
  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.
  
  
  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), Vo(2) (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 (r(2) = 0.84; P = 0.001).
  
  
  CONCLUSIONS
  Daily physical activity of patients with COPD is mainly associated with dynamic hyperinflation, regardless of severity classification.
authors: Servicio de Neumología, Hospital Universitario La Paz, Madrid, Spain. fgr01m@gmail.com
authors: Francisco
authors: F
authors: Garcia-Rio
authors: Vanesa
authors: V
authors: Lores
authors: Olga
authors: O
authors: Mediano
authors: Blas
authors: B
authors: Rojo
authors: Angel
authors: A
authors: Hernanz
authors: Eduardo
authors: E
authors: López-Collazo
authors: Rodolfo
authors: R
authors: Alvarez-Sala
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D003430:Cross-Sectional Studies; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods; D009043:Motor Activity / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012123:Pulmonary Ventilation / Q000502:physiology; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology; D012720:Severity of Illness Index; D016138:Walking / Q000502:physiology