Table 1 Inclusion and exclusion criteria

1. Chronic obstructive pulmonary disease + chronic respiratory failure

2. Long-term oxygen therapy

3. Clinical stability (7.35 < pH < 7.46)

1. Orthopaedic or neurological disease

2. Cognitive impairment (MMSE < 22)

3. Anamnestic history of ischemic heart disease or chronic heart failure

4. Pulmonary fibrosis