Background: Physical activity is known to cause significant deoxygenation in patients with severe chronic obstructive pulmonary disease (COPD). Although noninvasive positive pressure ventilation (NPPV) has been shown to improve oxygenation and physical activity in these patients, no practical approach for the application of NPPV during walking has yet been established.
Objective: To elucidate the most effective approach to preserving oxygenation during walking in patients with severe COPD receiving long-term NPPV.
Methods: Three 12-min walking tests were performed in a randomized cross-over design on 3 consecutive days, comparing the usual and double dosages of oxygen versus NPPV plus the usual dosage of oxygen. The ventilator and oxygen tank were placed in a backpack.
Results: Eleven patients (FEV(1) 26 +/- 9% predicted) completed the study, while 8 patients refused to walk with NPPV, due to the weight of the ventilatory device (7.3 kg with NPPV vs. 3.1 kg without). PaO(2) changes during walking differed [p = 0.01, repeated-measures (RM)-ANOVA], whereas dyspnea was unchanged. The difference in PaO(2) change was 14.0 +/- 16.6 mm Hg (unadjusted p = 0.0036, critical level = 0.017, RM-ANOVA) in favor of NPPV compared to the usual dosage of oxygen. Changes in FEV(1), tidal volume and inspiratory impedance were in favor of NPPV-aided exercise (all p < 0.05, RM-ANOVA). Walking distance was reduced under NPPV (555 +/- 227 m) compared to the usual (619 +/- 210 m) and double (622 +/- 215 m) dosages of oxygen (p = 0.024, RM-ANOVA).
Conclusions: NPPV plus supplemental oxygen, but not oxygen alone, preserves oxygenation during walking in patients with severe COPD. However, dyspnea and walking distance were not improved due to the burden of carrying the heavy ventilatory equipment in a backpack.