The overall objective of the study is to investigate the feasibility of home based inspiratory muscle training (IMT) on chronic hypercapnia in patients with severe COPD, and to examine the relationship between inspiratory muscle strength and carbon dioxide level.

The development of chronic hypercapnia in patients with COPD indicates an imbalance of increased ventilatory work caused by hyperinflation and airway resistance and a decreased inspiratory muscle reserve, probably caused by diaphragm- dysfunction. The inspiratory muscle strength can be trained by a devise, which provides a resistance to inspiration.

This study will be conducted as an a feasibility study and will examine whether inspiratory muscle training with a Power Breathe device (K3) is possible over a 6 week period in patients with COPD and chronic hypercapnia (pCO2 > 6 kilo pascal).

IMT will be considered as feasible if 80% of the planned training sessions have been completed, and if the maximum inspiratory strength improves by an average of 10% from MIP and if patients do not experience any discomfort or increased dyspnea during training.

The training of the respiratory strength is carried out daily with an electronic handheld device (Power Breathe K3) and will consist of 2x30 inspirations per day with the resistance adjusted individually and progressively with a pressure of 30 - 50% of maximal inspiratory pressure. Training will take place in the home.

Inclusion Criteria:

• Have the diagnosis COPD with FEV1 / FVC <0.70 and FEV1 <50%
• Have elevated pCO2 in stable phase assessed by arterial blood gas with pCO2> 6 kPa
• Have given informed consent
• Can understand written and oral instructions

Exclusion Criteria:

• Patients are included in other projects with impact on the carbon dioxide level, e.g. home noninvasive ventilation treatment
• Patients using variable oxygenation rate that may affect the carbon dioxide level.
• Unstable patients and at high risk of exacerbation during the investigation period
• Hospitalized patient with COPD exacerbation during the intervention period
• Patients with an expected need for change of COPD medication or oxygen supply equipment in the study period.

The participation in the study will be postponed if the patient is in a rehabilitation program