Home Mechanical Ventilation in Patients With Chronic Obstructive Pulmonary Disease (COPD) and Hypercapnic Response

The objective of this study is to evaluate the clinical benefits of home mechanical ventilation associated to oxygen therapy in COPD patients with chronic respiratory failure (CRF) who develop hypercapnia and nocturnal respiratory acidosis secondary to oxygen administration. We will include clinically stable COPD patients with hypercapnic CRF who develop a nocturnal hypercapnic response to oxygen (PaCO2 increase on awakening, at night with oxygen, \>10 mmHg respect to PaCO2 breathing room air and awake). Obstructive sleep apnoea syndrome (OSAS) will previously have been excluded. Patients will be admitted to the Pneumology ward where a nocturnal pulsioxymetry breathing oxygen therapy will be performed. Arterial blood gas samples will be taken at awakening (7AM). Patients who develop a hypercapnic response to oxygen will be randomised into 2 treatment groups: * Oxygen therapy group * Home mechanical ventilation plus oxygen therapy group Home mechanical ventilation will be performed with a bilevel pressure ventilator. Functional respiratory variables as well as quality of life and sleep at onset and after 6 months treatment will be compared. The principal outcome will be the evolution of arterial blood gases (PaCO2) between the two groups.