THE IMPACT OF EXERCISE RECONDITIONING ON BREATHLESSNESS IN SEVERE CHRONIC AIR-FLOW LIMITATION

Exercise in chronic airflow limitation (CAL) is often limited by symptoms before the physiologic boundaries of maximal ventilatory or cardiovascular capacities are attained. Symptom amelioration should translate directly into improved exercise performance. We studied the impact of a 6-wk supervised multimodality endurance exercise program (EXT) on perceived breathlessness (B) and leg effort (LE) and sought a physiologic rationale for symptom improvement. Thirty patients with CAL (FEV(1)/FVC = 42 +/- 2%, mean +/- SEM) were tested before and after EXT. Their responses were compared with those of a matched control group (n = 30; FEV(1)/FVC = 44 +/- 2%) after a nonintervention period. Testing included pulmonary function tests, chronic dyspnea evaluation (Baseline/Transition Dyspnea Index [BDI/TDI]), and graded cycle exercise with cardioventilatory monitoring and Borg scaling of B and LE. Spirometry did not change (Delta) post-EXT. EXT significantly (p < 0.001) reduced chronic breathlessness (TDI = +2.8 +/- 0.3) compared with control (TDI = 0.0 +/- 0.3). Exertional symptoms of B and LE also fell (p < 0.01) after EXT (slopes of B and LE relative to V over dot O-2 fell by 14 and 23%, respectively; Delta B/V over dot O-2 was associated with Delta LE/V over dot O-2, r = 0.52, p < 0.01). Post-EXT slopes of B over ventilation (V over dot E) also decreased by 10% (p < 0.025). Total cycle work increased 142 +/- 70% (p < 0.001) post-EXT and correlated primarily with Delta B/V over dot O-2 (r = -0.64, p < 0.001). The best correlate of Delta B/V over dot O-2 was Delta V over dot E/V over dot O-2 (r = 0.47, p < 0.001). V over dot E fell in proportion to V over dot CO2 at a standardized work rate (r = 0.91, p < 0.001), whereas efficiency improved (V over dot O-2/work rate slopes fell 12%, p < 0.01). In conclusion, supervised EXT effectively relieved both chronic and acute activity-related breathlessness in CAL, and thereby improved exercise tolerance. Relief of breathlessness was related to a fall in ventilatory demand during exercise as a result of enhanced mechanical efficiency. Reduced B for a given V over dot E after EXT may occur in part as a result of increased tolerance to the sensory perturbations that induce breathlessness in CAL.