Table 1: In- and exclusion criteria.

Inclusion Criteria	Exclusion Criteria
COPD
Daytime pCO2 > 7,0kPa, ph > 7,35 FEV1/FVC < 80% Established diagnosis of COPD according to GOLD Stable on inhaled medication	Worsened dyspnoea, cough, increased sputum production two weeks before entry oft the study Clinical signs of an exacerbation [22] Any other cause for hypercapnia Decompensated cor pulmonale Systemic corticosteroids
Obesity Hypoventilation
Daytime pCO2 > 7,0kPa, ph > 7,35 FVC < 70% BMI > 30kg/m2	FEV1/FVC < 80% Any other cause for hypercapnia Decompensated cor pulmonale