Determinants of exercise performance in normal men with externally imposed expiratory flow limitation

To understand how externally applied expiratory flow limitation (EFL) leads to impaired exercise performance and dyspnea, we studied six healthy males during control incremental exercise to exhaustion (C) and with EFL at ∼1. We measured volume at the mouth (Vm), esophageal, gastric and transdiaphragmatic (Pdi) pressures, maximal exercise power (W˙max) and the difference (Δ) in Borg scale ratings of breathlessness between C and EFL exercise. Optoelectronic plethysmography measured chest wall and lung volume (Vl). From Campbell diagrams, we measured alveolar (Pa) and expiratory muscle (Pmus) pressures, and from Pdi and abdominal motion, an index of diaphragmatic power (W˙di). Four subjects hyperinflated and two did not. EFL limited performance equally to 65%W˙max with Borg = 9–10 in both. At EFLW˙max, inspiratory time (Ti) was 0.66s ± 0.08, expiratory time (Te) 2.12 ± 0.26 s, Pmus ∼40 cmH2O and ΔVl-ΔVm = 488.7 ± 74.1 ml. From Pa and Vl, we calculated compressed gas volume (Vc) = 163.0 ± 4.6 ml. The differen...