Peak exercise workload ( WLpeak ) , dyspnea ( Borg ) , end-expiratory lung volume ( EELV ) , tidal volume ( VT ) , minute ventilation ( VE ) , O2 uptake ( VO2 ) , and CO2 production ( VCO2 ) were assessed in 10 COPD patients ( FEV1 53 22 % pred ) during three symptom-limited bicycle exercise tests while breathing i ) without a ventilator ( noPS ) , ii ) with a pressure support ( PS ) of 0 cm H2O ( PS0 ; IPAP & EPAP 4 cm H2O ) and iii ) PS of 10 cm H2O ( PS10 ; IPAP 14 & EPAP 4 cm H2O ) on separate days using a randomized crossover design .