Patient -Ventilator Interaction in Chronic Respiratory Failure

Inclusion Criteria: 1. Patients over the age of 16 years. 2. Patients with confirmed diagnosis of Duchenne Muscular dystrophy or Chronic Obstructive Pulmonary Disease or Obesity Hypoventilation Syndrome. 3. Patients with evidence of nocturnal hypoventilation with an arterial carbon dioxide partial pressure of \>6.0 kPa in the morning. 4. Patients with evidence of hypercapnic respiratory failure with an arterial carbon dioxide partial pressure of \>6.0 kPa during the day. 5. No prior domiciliary ventilation. Exclusion Criteria: 1. Patients with other co-morbidities e.g. cancer or cardiac failure. 2. Patients with muscular weakness but an unconfirmed diagnosis of Duchenne Muscular Dystrophy, Obesity Hypoventilation Syndrome or Chronic Obstructive Pulmonary Disease. 3. Patients who have had an acute illness within the last 4 weeks prior to starting assessment for ventilation. 4. Patients who have an abnormal bleeding tendency (INR or APTTr \>1.4 or platelets \<100). 5. Patients with a psychological, social or geographical situation that would impair compliance with the project.