Introduction/Purpose: Hyperpnea and hyperinflation have been proposed as contributors to exaggerated energy demands in chronic obstructive pulmonary disease (COPD), yet there are incomplete data on exercise requirements. This study compared total-body energy demands of the internal (unloaded) and external work of cycling and delta mechanical efficiency in 40 patients (FEV1: 36 ± 14% predicted) with COPD and 28 healthy age-matched controls while characterizing dynamic hyperinflation.
Methods: Steady-state V˙O2 was obtained at rest, during unloaded and 20-W cycling, and at 20, 50, and 65% peak cycling power. Delta mechanical efficiency was calculated between constant-load cycling at 65 and 20% peak power. Dynamic hyperinflation was assessed from inspiratory capacity maneuvers.
Results: Oxygen demands (L·min−1) at rest, for internal work (0.47 ± 0.14 vs 0.45 ± 0.11) or external work at 20 W (0.62 ± 0.20 vs 0.57 ± 0.13), were not different between patients and controls, although ventilation was elevated in COPD. Cycling at 65% of peak power induced dynamic hyperinflation in COPD, which indices were not related to cycling efficiency. Delta efficiency (%) was not different between patients (26.3 ± 8.1) and controls (24.8 ± 4.0).
Conclusion: Findings suggest that bioenergetics of submaximal cycling is not compromised in moderately severe COPD despite tachypnea and dynamic hyperinflation.