• Exercise endurance [ Time Frame: 8 weeks ] [ Designated as safety issue: No ]
  

Dynamic hyperinflation limits exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). Recently, several innovative approaches have been developed to reduce the burden of dynamic hyperinflation. Two such innovations, ventilation-feedback training and Heliox supplementation during exercise show great promise and posit a reduction in dynamic hyperinflation as a key to their effectiveness. In our recently completed trial, when age, FEV1 and RV/TLC were controlled, exercise plus VF (E+VF) was superior to E training alone (E only) or VF training alone in improving exercise tolerance. The mechanism responsible for this difference was, in part, a reduction in exercise-induced dynamic hyperinflation secondary to a change in breathing pattern. In additional preliminary studies, we determined that exercise tolerance can be increased when patients exercise while inhaling Heliox. Similar to VF, the mechanism for exercise improvement with Heliox was a reduction in exercise-induced dynamic hyperinflation. Although both interventions are promising, there are no definitive data to support use of either intervention as a standard of care for pulmonary rehabilitation. The goal of our new proposal is to compare E+VF to E only and to compare E+Heliox to E only. We hope to provide definitive evidence whether either or both interventions are superior to E only. As a secondary objective, we will compare the two interventions "head to head" using the same rigorous research methods.

Hypothesis/Research Questions Overview: The two primary hypotheses are that patients with moderate-severe COPD who successfully complete eight weeks of (a) E+VF training will achieve longer exercise duration than patients randomly assigned to E only and (b) E+heliox training will achieve longer exercise duration than patients randomly assigned to E only. Next, we hypothesize that the primary mechanism/predictor responsible for the increased exercise performance in all patients will be a reduction in dynamic hyperinflation and not a difference in exercise-induced adaptation of the respiratory or peripheral muscles.

Methods: This study is a randomized controlled clinical trial. After baseline testing is completed, 135 subjects with moderate-severe COPD will be randomized into one of three groups: E+VF, E+Heliox and E training only. Follow-up testing will be completed at 8 weeks. Additionally, in order to assess carryover effects of each training program, subjects will be asked to return to the testing facility at 14 weeks for follow-up assessments. Testing will include a pulmonary function test, two symptom-limited treadmill tests, two constant work-rate tests (CWR), maximal inspiratory and expiratory pressures, respiratory muscle endurance, tissue spectrometry, quadriceps muscle endurance testing, activity monitoring, and dyspnea measurements. After baseline testing is completed, randomized subjects will train in the Physical Performance Laboratory three times weekly. Exercise prescriptions will be standardized and based on data from the exercise stress test. Measures of central tendency will be used to describe changes in physiological parameters pre-and post-treatment.

Analysis: A two-sample t-test with Bonferroni adjustment of the alpha level (a = 0.025) for each pairwise comparison will be used to analyze changes in treadmill CWR duration from baseline to 8-weeks between the E+VF and E only and the E+Heliox and training will achieve longer exercise duration than patients randomly assigned to E only groups. Multiple regression procedures will be employed to determine the predictors of improved exercise performance.