Hypothesis: Hospital based, comprehensive pulmonary rehabilitation of patients with COPD in GOLD stage IV can be optimized by application of nocturnal non invasive ventilation.

This hypotheses shall be tested by an observational trial, comparing rehabilitation effects of a prospectively observed group receiving non invasive ventilation, compared wiht a historical control group of patients who did received the same treatment without non invasive ventilation.

Non invasive ventilation is known to allow improvements if applied during endurance training, but this is technically difficult. Nocturnal application of non invasive ventilation is known to unload the ventilatory pump, reset the control of breathing, and improve sleep quality.

The protocol also aimed to evaluate the acceptance of non invasive ventilation in patients undergoing a four week inpatient pulmonary rehabilitation programme.

Inclusion Criteria:

• Confirmed diagnosis of COPD in stages GOLD IV
• Receiving optimized medical treatment and long term oxygen treatment, if indicated
• Patient's consent to participate in this trial

Exclusion Criteria:

• Previous treatment with NIPPV
• Unwillingness or intolerance to perform NIPPV
• Acute exacerbation of COPD at baseline or during pulmonary rehabilitation,
• Significant orthopaedic or neurologic problems that reduce mobility or cooperation with physical training
• Poor controlled coexisting psychiatric or unstable cardiac disease,
• Inability to perform a six minute walk test
• Extreme hypercapnia (pCO2 > 74 mmHg)

All patients were recruited at a single center, the rehabilitation hospital "Klinikum Berchtesgadener Land" at Germany.

Patients entering the well defined, hospital based pulmonary rehabilitation programme after Januar 1, 2005 were additionally treated with nocturnal non invasive ventilation. The results of these patients were compared with a group of patients who underwent the same rehabilitation programme in the years 2003 to 2005, when non invasive ventilation was not availabe.