It is known from various other studies with other patient collectives with nocturnal positive pressure therapy, like patients with obstructive sleep apnoea syndrome, that only 50 to 70% of those patients are using their therapy constantly. Daily practice shows that patients with chronic hypercapnia based on COPD are even harder to accustom oneself to a nocturnal breathing therapy than patients with restrictive lung diseases or patients with obstructive sleep apnoea syndrome.