Effects of L-arginine and Liposomial Vitamin C on Severe Copd Patients Undergoing Pulmonary Rehabilitation.

Inclusion criteria: * COPD patients of both sexes complicated by respiratory failure (PaO2 inferior to 60 mmHg while breathing room air) * aged between 40 and 90 years selected from the inpatient/outpatient population admitted to perform a PR program in 12 Italian rehabilitation hospitals. Exclusion criteria: * consuming any ergogenic supplement in the last 2 months; * severe acute exacerbations in the 3 months before enrolment; * clinical instability (pH inferior to 7.35, hemodynamic instability, tachypnea at rest); * lung restrictive diseases; * primitive pulmonary hypertension; * recent lung thromboembolic events; * orthopaedic clinical conditions interfering with exercise; * coronary heart disease; * cardiac failure with reduced ejection fraction; * major cardiac arrhythmias; * neuromuscular diseases; * mini mental state examination (MMSE) \<24; * any prior or current medical problem that would limit the subject participation