Peak exercise workload ( WLpeak ) , dyspnea ( Borg ) , end-expiratory lung volume ( EELV ) , tidal volume ( VT ) , minute ventilation ( VE ) , O@ uptake ( VO@ ) , and CO@ production ( VCO@ ) were assessed in @ COPD patients ( FEV@ @ @ % pred ) during three symptom-limited bicycle exercise tests while breathing i ) without a ventilator ( noPS ) , ii ) with a pressure support ( PS ) of @ cm H@O ( PS@ ; IPAP & EPAP @ cm H@O ) and iii ) PS of @ cm H@O ( PS@ ; IPAP @ & EPAP @ cm H@O ) on separate days using a randomized crossover design .