Ambulatory Adaptation to Non-Invasive Mechanical Ventilation

Inclusion Criteria: 1. Age between 18 and 75 2. Chronic respiratory insufficiency secondary to neuromuscular disease or thoracic cage alterations with indication of non-invasive mechanical ventilation (presence of fatigue, dyspnea, morning headache, etc) plus one of the following criteria): * PaCO2 \> 45 mmHg * Night time oxygen saturation \< 88% at least for 5 consecutive minutes * In neuromuscular diseases, PIM \< 60 cmH2O or FVC \< 50% of theoretical. 3. Stable disease. 4. Airway access through nasal mask. 5. Ability to provide written informed consent. 6. Ability to attend the visits Exclusion Criteria: 1. Contraindications for mechanical ventilation: * Patient with terminal disease or vegetative state * Lack of motivation of the patient * Lack of family or social support * Patients clinically unstable * Agitation or lack of co-operation * Depression. 2. Patients with acute symptoms requiring hospital admission. 3. Need for airway access through tracheostomy, face mask or mouth piece. 4. Relevant comorbidity (ie. heart failure, diabetes non controlled, infections, malignancies, etc.) leading to difficulties in adaptation to ventilation. 5. Use (for 7 days or more) of CNS depressors(benzodiazepines, antihistamines H1, tricyclic antidepressants , antiepileptic or antipsychotic drugs ) in the 30-day period prior to inclusion, or expected need for such drugs during the study. 6. Lack of understanding of the study procedures.