Fig. 3From: Portable NIV for patients with moderate to severe COPD: two randomized crossover trialsa Study I: Borg Dyspnea difference before and after the 6-min walking test, with and without the pNIV device (N = 38). Abreviation: w/o without. b Study II: Borg Dyspnea difference before and after 6-min walking test, with and without the pNIV device (N = 23). Abreviation: w/o withoutBack to article page