Patients aged 30–75 years with very severe COPD (GOLD IV),
with and without the presence of chronic respiratory failure, were
recruited prospectively. Exclusion criteria were resting capillary
PCCO2 >55 mmHg, use of non-invasive ventilation, and/or acute
exacerbation in the last 4 weeks. The Bavarian ethical committee
approved this study and all subjects provided written informed
consent (Germany: Ethic committee approval number: 12007).
Sixty-two (n = 62) out of 75 patients with very severe COPD, participating in an inpatient Pulmonary Rehabilitation at Schoen Klinik
Berchtesgadener Land (Schoenau am Koenigssee, Germany) were
used for data analyses. Data from 13 patients were incomplete, and,
in turn, not used for further analyses.